/* =====================================================================
   数学十六年 · 样式
   浅色 = 坐标纸 + 红笔批改；深色 = 黑板 + 粉笔
   ===================================================================== */
:root {
  color-scheme: light;
  --paper: #F1F5F2;
  --paper-grid: rgba(28, 105, 76, .075);
  --card: #FFFFFF;
  --card-2: #F7FAF8;
  --card-3: #E9F0EB;
  --line: #D2DDD6;
  --line-2: #E3EBE6;
  --ink: #14212A;
  --ink-2: #3B4B55;
  --ink-3: #687A84;
  --red: #C8302B;
  --on-red: #FFFFFF;
  --red-soft: rgba(200, 48, 43, .08);
  --hl: #FFE98A;
  --note-bg: #FFF9DB;
  --note-line: #E8D78C;
  --note-ink: #2A2410;
  --good: #1B8452;
  --good-soft: rgba(27, 132, 82, .1);
  --bad: #C8302B;
  --bad-soft: rgba(200, 48, 43, .07);
  --grid: rgba(20, 33, 42, .075);
  --grid-major: rgba(20, 33, 42, .16);
  --axis: #4A5963;
  --c1: #2360C0; --c2: #D46A12; --c3: #1B8452; --c4: #C8302B; --c5: #7043BA; --c6: #0A8494;
  --st-primary: #CC6415; --st-junior: #1B8452; --st-senior: #2360C0; --st-college: #7043BA;
  --accent: #14212A;
  --on-accent: #FFFFFF;
  --shadow: 0 1px 0 rgba(20, 33, 42, .03), 0 12px 30px -20px rgba(20, 33, 42, .35);
  --f-display: "Noto Serif SC", "Source Han Serif SC", "Songti SC", "STSong", "SimSun", serif;
  --f-brush: "Ma Shan Zheng", "STKaiti", "KaiTi", "Kaiti SC", "Noto Serif SC", serif;
  --f-body: -apple-system, BlinkMacSystemFont, "PingFang SC", "HarmonyOS Sans SC", "Microsoft YaHei", "Noto Sans SC", "Source Han Sans SC", "Helvetica Neue", Arial, sans-serif;
  --f-mono: "JetBrains Mono", ui-monospace, "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  --top-h: 64px;
  /* 字号倍率（宽屏放大一点，见下方 @media）；页面左右留白 */
  --fs: 1;
  --gutter: 20px;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    color-scheme: dark;
    --paper: #102019;
    --paper-grid: rgba(220, 244, 230, .035);
    --card: #162A21;
    --card-2: #1A3027;
    --card-3: #20382E;
    --line: #2A443A;
    --line-2: #22392F;
    --ink: #E9F0EA;
    --ink-2: #B4C4BB;
    --ink-3: #87998F;
    --red: #FF8E83;
    --on-red: #10201A;
    --red-soft: rgba(255, 142, 131, .1);
    --hl: rgba(255, 222, 102, .32);
    --note-bg: rgba(255, 226, 120, .06);
    --note-line: rgba(255, 226, 120, .28);
    --note-ink: #F5E7A9;
    --good: #7FD6A3;
    --good-soft: rgba(127, 214, 163, .12);
    --bad: #FF8E83;
    --bad-soft: rgba(255, 142, 131, .1);
    --grid: rgba(233, 240, 234, .07);
    --grid-major: rgba(233, 240, 234, .15);
    --axis: #A5B7AD;
    --c1: #8BBCF7; --c2: #F4B26A; --c3: #7FD6A3; --c4: #FF8E83; --c5: #C5A7F5; --c6: #6ED2DA;
    --st-primary: #F4B26A; --st-junior: #7FD6A3; --st-senior: #8BBCF7; --st-college: #C5A7F5;
    --accent: #E9F0EA;
    --on-accent: #10201A;
    --shadow: 0 1px 0 rgba(0, 0, 0, .25), 0 14px 34px -20px rgba(0, 0, 0, .7);
  }
}
:root[data-theme="dark"] {
  color-scheme: dark;
  --paper: #102019;
  --paper-grid: rgba(220, 244, 230, .035);
  --card: #162A21;
  --card-2: #1A3027;
  --card-3: #20382E;
  --line: #2A443A;
  --line-2: #22392F;
  --ink: #E9F0EA;
  --ink-2: #B4C4BB;
  --ink-3: #87998F;
  --red: #FF8E83;
  --on-red: #10201A;
  --red-soft: rgba(255, 142, 131, .1);
  --hl: rgba(255, 222, 102, .32);
  --note-bg: rgba(255, 226, 120, .06);
  --note-line: rgba(255, 226, 120, .28);
  --note-ink: #F5E7A9;
  --good: #7FD6A3;
  --good-soft: rgba(127, 214, 163, .12);
  --bad: #FF8E83;
  --bad-soft: rgba(255, 142, 131, .1);
  --grid: rgba(233, 240, 234, .07);
  --grid-major: rgba(233, 240, 234, .15);
  --axis: #A5B7AD;
  --c1: #8BBCF7; --c2: #F4B26A; --c3: #7FD6A3; --c4: #FF8E83; --c5: #C5A7F5; --c6: #6ED2DA;
  --st-primary: #F4B26A; --st-junior: #7FD6A3; --st-senior: #8BBCF7; --st-college: #C5A7F5;
  --accent: #E9F0EA;
  --on-accent: #10201A;
  --shadow: 0 1px 0 rgba(0, 0, 0, .25), 0 14px 34px -20px rgba(0, 0, 0, .7);
}
[data-stage="primary"] { --accent: var(--st-primary); }
[data-stage="junior"] { --accent: var(--st-junior); }
[data-stage="senior"] { --accent: var(--st-senior); }
[data-stage="college"] { --accent: var(--st-college); }

/* ---------- 基础 ---------- */
*, *::before, *::after { box-sizing: border-box; }
[hidden] { display: none !important; }
/* 布局：默认“标准”（页面最宽 1340px、原字号）；<html data-layout="wide"> 是“宽屏”：铺满屏幕，电脑上字放大 10%（手机字号不变）。顶栏按钮切换，记在本机 */
:root[data-layout="wide"] { --gutter: clamp(16px, 2.6vw, 48px); }
@media (min-width: 900px) { :root[data-layout="wide"] { --fs: 1.1; } }
html { -webkit-text-size-adjust: 100%; scroll-padding-top: calc(var(--top-h) + 16px); }
body {
  margin: 0;
  background-color: var(--paper);
  background-image:
    linear-gradient(var(--paper-grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--paper-grid) 1px, transparent 1px);
  background-size: 28px 28px;
  color: var(--ink);
  font: calc(16px * var(--fs))/1.75 var(--f-body);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
#app { min-height: 100vh; display: flex; flex-direction: column; }
a { color: inherit; }
button, input, select { font: inherit; color: inherit; }
button { cursor: pointer; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 4px; }
.sr { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
.mono { font-family: var(--f-mono); }
.katex { font-size: 1.08em; }
.katex-display { margin: .55em 0; overflow-x: auto; overflow-y: hidden; padding: 2px 0; }
.tex-raw { font-family: var(--f-mono); font-size: .9em; color: var(--ink-2); }

/* ---------- 顶栏 ---------- */
.topbar {
  position: sticky; top: env(safe-area-inset-top, 0px); z-index: 40;
  background: color-mix(in srgb, var(--paper) 90%, transparent);
  -webkit-backdrop-filter: saturate(1.2) blur(10px); backdrop-filter: saturate(1.2) blur(10px);
  border-bottom: 1px solid var(--line);
}
.topbar-in { max-width: 1340px; margin: 0 auto; padding: 10px var(--gutter); display: flex; align-items: center; gap: 10px 18px; flex-wrap: wrap; }
.brand { display: inline-flex; align-items: center; gap: 10px; text-decoration: none; flex: 0 0 auto; }
.seal {
  width: 36px; height: 36px; border-radius: 5px; background: var(--red); color: var(--on-red);
  display: grid; place-items: center; font-family: var(--f-brush); font-size: calc(25px * var(--fs)); line-height: 1;
  box-shadow: inset 0 0 0 2px var(--red), inset 0 0 0 3.5px var(--on-red);
  transform: rotate(-4deg);
}
.brand-name { display: flex; flex-direction: column; line-height: 1.15; }
.brand-name b { font-family: var(--f-display); font-weight: 900; font-size: calc(19px * var(--fs)); letter-spacing: .04em; }
.brand-name small { font: 500 calc(10.5px * var(--fs)) var(--f-mono); color: var(--ink-3); letter-spacing: .08em; }
.tabs { display: flex; gap: 2px; padding: 3px; background: var(--card-3); border: 1px solid var(--line); border-radius: 10px; overflow-x: auto; scrollbar-width: none; }
.tabs::-webkit-scrollbar { display: none; }
.tab { --tab-c: var(--ink); display: flex; flex-direction: column; align-items: flex-start; padding: 4px 14px 5px; border-radius: 7px; text-decoration: none; color: var(--ink-2); line-height: 1.3; white-space: nowrap; transition: background .15s, color .15s; }
.tab b { font-family: var(--f-display); font-weight: 900; font-size: calc(15px * var(--fs)); letter-spacing: .06em; }
.tab small { font: 500 calc(10.5px * var(--fs)) var(--f-mono); color: var(--ink-3); }
.tab:hover { background: color-mix(in srgb, var(--card) 60%, transparent); }
.tab[aria-current="page"] { background: var(--card); color: var(--tab-c); box-shadow: 0 1px 2px rgba(0, 0, 0, .08), inset 0 -2px 0 var(--tab-c); }
.tab[data-s="primary"] { --tab-c: var(--st-primary); }
.tab[data-s="junior"] { --tab-c: var(--st-junior); }
.tab[data-s="senior"] { --tab-c: var(--st-senior); }
.tab[data-s="college"] { --tab-c: var(--st-college); }
.top-tools { margin-left: auto; display: flex; align-items: center; gap: 8px; flex: 1 1 340px; max-width: 600px; min-width: 0; }
.search { position: relative; flex: 1 1 auto; min-width: 0; }
.search input {
  width: 100%; height: 38px; border: 1px solid var(--line); background: var(--card); border-radius: 8px;
  padding: 0 12px 0 34px; font-size: calc(14px * var(--fs)); color: var(--ink);
}
.search input::placeholder { color: var(--ink-3); }
.search svg { position: absolute; left: 11px; top: 11px; width: 16px; height: 16px; color: var(--ink-3); pointer-events: none; }
.results {
  position: absolute; top: calc(100% + 6px); right: 0; width: min(440px, calc(100vw - 32px)); max-height: 62vh; overflow: auto;
  background: var(--card); border: 1px solid var(--line); border-radius: 10px; box-shadow: var(--shadow); padding: 6px; z-index: 60;
}
.res { display: grid; grid-template-columns: auto 1fr; gap: 0 10px; padding: 8px 10px; border-radius: 7px; text-decoration: none; align-items: baseline; }
.res:hover, .res.on { background: var(--card-3); }
.res-st { font: 600 calc(11px * var(--fs)) var(--f-mono); padding: 2px 6px; border-radius: 4px; border: 1px solid currentColor; }
.res-t { font-weight: 600; font-size: calc(14.5px * var(--fs)); }
.res-c { grid-column: 2; font-size: calc(12.5px * var(--fs)); color: var(--ink-3); }
.res-empty { padding: 14px; color: var(--ink-3); font-size: calc(14px * var(--fs)); }
.st-primary { color: var(--st-primary); } .st-junior { color: var(--st-junior); } .st-senior { color: var(--st-senior); } .st-college { color: var(--st-college); }
.icon-btn { flex: 0 0 auto; display: inline-flex; align-items: center; gap: 6px; height: 38px; padding: 0 12px; border: 1px solid var(--line); background: var(--card); border-radius: 8px; font-size: calc(13.5px * var(--fs)); font-weight: 600; color: var(--ink); white-space: nowrap; }
.icon-btn:hover { border-color: var(--ink-3); }
#topLayout[aria-pressed="true"] { background: var(--accent); border-color: var(--accent); color: var(--on-accent); }
/* 屏幕不够宽时两种布局看起来一样，不显示切换按钮 */
@media (max-width: 1100px) { #topLayout { display: none; } }
.login-btn { flex: 0 0 auto; white-space: nowrap; }

/* ---------- 通用 ---------- */
.wrap { width: 100%; max-width: 1340px; margin: 0 auto; padding-inline: var(--gutter); padding-block: 28px 72px; flex: 1 0 auto; }
.eyebrow { font: 600 calc(12.5px * var(--fs))/1.5 var(--f-body); letter-spacing: .06em; color: var(--ink-3); margin: 0 0 10px; }
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px; min-height: 42px; padding: 0 18px;
  border-radius: 8px; border: 1px solid var(--line); background: var(--card); color: var(--ink);
  font-size: calc(15px * var(--fs)); font-weight: 600; text-decoration: none; transition: transform .12s, border-color .12s, background .12s;
}
.btn:hover { border-color: var(--ink-3); }
.btn:active { transform: translateY(1px); }
.btn.primary { background: var(--accent); color: var(--on-accent); border-color: var(--accent); }
.btn.primary:hover { filter: brightness(1.08); }
.btn.sm { min-height: 34px; padding: 0 12px; font-size: calc(13.5px * var(--fs)); }
.btn.ghost { background: transparent; }
.prog { display: flex; align-items: center; gap: 10px; font-size: calc(12.5px * var(--fs)); color: var(--ink-3); }
.prog-bar { flex: 1; height: 6px; border-radius: 3px; background: var(--card-3); overflow: hidden; min-width: 60px; }
.prog-bar i { display: block; height: 100%; width: 0; background: var(--red); border-radius: 3px; transition: width .4s; }
.prog b { color: var(--ink); font-variant-numeric: tabular-nums; }

/* ---------- 首页 ---------- */
.hero { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 520px); gap: 28px 48px; align-items: center; padding-block: 18px 8px; }
.hero h1 { font-family: var(--f-display); font-weight: 900; font-size: clamp(36px, 5.2vw, 62px); line-height: 1.14; letter-spacing: -.005em; margin: 0; text-wrap: balance; }
.hero h1 em { font-style: normal; color: var(--red); background: linear-gradient(transparent 78%, var(--red-soft) 78%); }
.lede { font-size: calc(17px * var(--fs)); line-height: 1.85; color: var(--ink-2); max-width: 33em; margin: 18px 0 0; }
.hero-cta { display: flex; gap: 10px; flex-wrap: wrap; margin-top: 26px; }
figure { margin: 0; }
.hero-demo { margin: 0; min-width: 0; background: var(--card); border: 1px solid var(--line); border-radius: 12px; box-shadow: var(--shadow); overflow: hidden; }
.hero-demo .demo-cap { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: baseline; gap: 2px 10px; padding: 10px 16px; border-bottom: 1px solid var(--line-2); font-size: calc(13px * var(--fs)); color: var(--ink-3); }
.hero-demo .demo-cap b { color: var(--ink); font-size: calc(14px * var(--fs)); }
.hero-demo .ma-canvas { background: var(--card); }

.path { margin-top: 48px; }
.path-head { display: flex; justify-content: space-between; align-items: baseline; gap: 12px; flex-wrap: wrap; margin-bottom: 12px; }
.path-head h2 { font-family: var(--f-display); font-weight: 900; font-size: calc(24px * var(--fs)); margin: 0; }
.path-head p { margin: 0; color: var(--ink-3); font-size: calc(14px * var(--fs)); }
.ruler { display: grid; grid-template-columns: repeat(16, minmax(0, 1fr)); background: var(--card); border: 1px solid var(--line); border-radius: 6px; overflow: hidden; }
.yr {
  --sc: var(--ink-3); position: relative; padding: 18px 0 12px 7px; border-left: 1px solid var(--line-2); min-width: 0;
  background-image: repeating-linear-gradient(90deg, var(--ink-3) 0 1px, transparent 1px 10%);
  background-size: 100% 6px; background-repeat: no-repeat; background-position: 0 0;
}
.yr:first-child { border-left: 0; }
.yr::before { content: ""; position: absolute; left: -1px; top: 0; width: 1.5px; height: 13px; background: var(--ink); }
.yr::after { content: ""; position: absolute; left: 0; right: 0; bottom: 0; height: 4px; background: var(--sc); }
.yr-n { display: block; font: 700 calc(14px * var(--fs))/1 var(--f-mono); color: var(--sc); }
.yr-g { display: block; margin-top: 4px; font-size: calc(11.5px * var(--fs)); color: var(--ink-3); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.yr[data-s="primary"] { --sc: var(--st-primary); } .yr[data-s="junior"] { --sc: var(--st-junior); }
.yr[data-s="senior"] { --sc: var(--st-senior); } .yr[data-s="college"] { --sc: var(--st-college); }
.stage-cards { display: grid; grid-template-columns: 6fr 3fr 3fr 4fr; gap: 12px; margin-top: 12px; }
.stage-card {
  --sc: var(--ink); display: flex; flex-direction: column; gap: 10px; padding: 16px 16px 18px; min-width: 0;
  background: var(--card); border: 1px solid var(--line); border-radius: 10px; text-decoration: none; color: var(--ink);
  transition: transform .18s, box-shadow .18s, border-color .18s;
}
.stage-card:hover { transform: translateY(-3px); box-shadow: var(--shadow); border-color: var(--sc); }
.stage-card[data-s="primary"] { --sc: var(--st-primary); } .stage-card[data-s="junior"] { --sc: var(--st-junior); }
.stage-card[data-s="senior"] { --sc: var(--st-senior); } .stage-card[data-s="college"] { --sc: var(--st-college); }
.sc-top { display: flex; align-items: baseline; justify-content: space-between; gap: 8px; flex-wrap: wrap; }
.sc-name { font-family: var(--f-brush); font-size: calc(46px * var(--fs)); line-height: 1; color: var(--sc); }
.sc-grades { font: 600 calc(12px * var(--fs)) var(--f-mono); color: var(--ink-3); }
.sc-canvas { height: 168px; border-radius: 7px; background: var(--card-2); border: 1px solid var(--line-2); overflow: hidden; }
.sc-canvas .ma-canvas { background: transparent; }
.sc-canvas .ma-ui { display: none; }
.sc-classic { font-size: calc(13px * var(--fs)); line-height: 1.6; color: var(--ink-2); }
.sc-classic b { font-family: var(--f-display); font-weight: 900; color: var(--ink); margin-right: 6px; }
.sc-blurb { margin: 0; font-size: calc(14px * var(--fs)); line-height: 1.7; color: var(--ink-2); }
.sc-stats { display: flex; gap: 14px; flex-wrap: wrap; font-size: calc(13px * var(--fs)); color: var(--ink-3); margin-top: auto; }
.sc-stats b { font: 700 calc(18px * var(--fs)) var(--f-mono); color: var(--ink); margin-right: 2px; font-variant-numeric: tabular-nums; }
.sc-go { font-weight: 700; font-size: calc(14px * var(--fs)); color: var(--sc); }

.howto { margin-top: 56px; display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 12px; }
.how { background: var(--card); border: 1px solid var(--line); border-radius: 10px; padding: 18px 18px 16px; }
.how-k { display: flex; align-items: center; gap: 12px; margin-bottom: 8px; }
.how-k span { font-family: var(--f-brush); font-size: calc(40px * var(--fs)); line-height: 1; color: var(--red); }
.how-k b { font-family: var(--f-display); font-weight: 900; font-size: calc(17px * var(--fs)); }
.how-k i { font: 600 calc(12px * var(--fs)) var(--f-mono); font-style: normal; color: var(--ink-3); margin-left: auto; }
.how p { margin: 0; font-size: calc(14px * var(--fs)); color: var(--ink-2); line-height: 1.7; }
.home-more { margin-top: 44px; display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: 12px; }
.panel { background: var(--card); border: 1px solid var(--line); border-radius: 10px; padding: 18px 20px; }
.panel h3 { font-family: var(--f-display); font-weight: 900; font-size: calc(18px * var(--fs)); margin: 0 0 10px; }
.panel p { margin: 0 0 12px; color: var(--ink-2); font-size: calc(14.5px * var(--fs)); }
.sheet-links { display: flex; gap: 8px; flex-wrap: wrap; }
.today { display: block; text-decoration: none; padding: 14px 16px; border: 1px dashed var(--line); border-radius: 8px; background: var(--card-2); }
.today .t { font-family: var(--f-display); font-weight: 900; font-size: calc(18px * var(--fs)); display: block; margin: 2px 0 4px; }
.today .s { font-size: calc(14px * var(--fs)); color: var(--ink-2); }
.today:hover { border-color: var(--ink-3); }

/* ---------- 学段页 ---------- */
.stage-view { display: grid; grid-template-columns: 276px minmax(0, 1fr); gap: 36px; align-items: start; }
.rail { position: sticky; top: calc(env(safe-area-inset-top, 0px) + var(--top-h) + 16px); max-height: calc(100vh - var(--top-h) - 32px); overflow: auto; scrollbar-width: thin; padding-right: 4px; }
.rail-head { background: var(--card); border: 1px solid var(--line); border-radius: 10px; padding: 16px 16px 14px; }
.rail-name { display: flex; align-items: baseline; justify-content: space-between; gap: 8px; }
.rail-name b { font-family: var(--f-brush); font-weight: 400; font-size: calc(44px * var(--fs)); line-height: 1; color: var(--accent); }
.rail-name small { font: 600 calc(12px * var(--fs)) var(--f-mono); color: var(--ink-3); }
.rail-head .prog { margin-top: 12px; }
.rail-actions { display: flex; gap: 8px; margin-top: 12px; flex-wrap: wrap; }
.rail-actions .btn { flex: 1 1 auto; }
.ch-select-wrap { display: none; margin-top: 12px; }
.ch-select-wrap select { width: 100%; height: 42px; border-radius: 8px; border: 1px solid var(--line); background: var(--card); padding: 0 10px; font-size: calc(15px * var(--fs)); }
.ch-list { display: flex; flex-direction: column; gap: 2px; margin-top: 12px; }
.ch-link { display: grid; grid-template-columns: 26px 1fr auto; gap: 8px; align-items: baseline; padding: 8px 10px; border-radius: 8px; text-decoration: none; color: var(--ink-2); line-height: 1.4; }
.ch-link:hover { background: color-mix(in srgb, var(--card) 70%, transparent); color: var(--ink); }
.ch-link.on { background: var(--card); color: var(--ink); box-shadow: inset 2px 0 0 var(--accent); }
.ch-no { font: 600 calc(12px * var(--fs)) var(--f-mono); color: var(--ink-3); }
.ch-link.on .ch-no { color: var(--accent); }
.ch-t { font-size: calc(14.5px * var(--fs)); font-weight: 600; min-width: 0; }
.ch-t small { display: block; font-weight: 400; font-size: calc(12px * var(--fs)); color: var(--ink-3); }
.ch-p { font: 500 calc(11.5px * var(--fs)) var(--f-mono); color: var(--ink-3); font-variant-numeric: tabular-nums; }
.ch-p.full { color: var(--red); }

.chapter { min-width: 0; max-width: 940px; }
.ch-head { padding: 4px 0 6px; }
.ch-head h2 { font-family: var(--f-display); font-weight: 900; font-size: clamp(28px, 3.6vw, 42px); line-height: 1.2; margin: 0 0 10px; text-wrap: balance; }
.ch-intro { font-size: calc(16.5px * var(--fs)); color: var(--ink-2); max-width: 44em; margin: 0; }
.pt-index { display: flex; flex-wrap: wrap; gap: 6px 8px; margin-top: 16px; }
.pi { font-size: calc(13px * var(--fs)); line-height: 1.5; padding: 4px 11px; border-radius: 999px; border: 1px solid var(--line); background: var(--card); text-decoration: none; color: var(--ink-2); }
.pi:hover { border-color: var(--accent); color: var(--ink); }
.pi.done { border-color: var(--red); color: var(--red); }
.pi.done::before { content: "✓ "; font-weight: 700; }
.pi .katex { font-size: 1em; }

/* ---------- 知识点卡片 ---------- */
.pt { position: relative; background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 26px 30px 28px; margin-top: 22px; box-shadow: var(--shadow); scroll-margin-top: calc(var(--top-h) + 16px); }
.pt.flash { animation: ptflash 1.6s ease-out; }
@keyframes ptflash { 0% { box-shadow: 0 0 0 3px var(--accent), var(--shadow); } 100% { box-shadow: 0 0 0 0 transparent, var(--shadow); } }
.pt-head { position: relative; padding-right: 96px; }
.pt-meta { display: flex; align-items: center; flex-wrap: wrap; gap: 6px; }
.pt-no { font: 700 calc(12.5px * var(--fs)) var(--f-mono); color: var(--accent); margin-right: 4px; }
.chip { font-size: calc(12px * var(--fs)); line-height: 1; padding: 5px 8px; border-radius: 4px; background: var(--card-3); color: var(--ink-2); white-space: nowrap; }
.chip.grade { background: transparent; box-shadow: inset 0 0 0 1px var(--accent); color: var(--accent); font-weight: 600; }
.pt-title { font-family: var(--f-display); font-weight: 900; font-size: clamp(22px, 2.5vw, 27px); line-height: 1.32; margin: 10px 0 6px; text-wrap: balance; }
.pt-sum { color: var(--ink-2); margin: 0; font-size: calc(16.5px * var(--fs)); }
.stamp-btn {
  position: absolute; top: -4px; right: -8px; width: 82px; height: 82px; border-radius: 50%;
  border: 1.5px dashed var(--line); background: transparent; color: var(--ink-3);
  font-size: calc(12.5px * var(--fs)); font-weight: 600; line-height: 1.3; display: grid; place-items: center; text-align: center;
  transition: border-color .15s, color .15s, background .15s;
}
.stamp-btn:hover { border-color: var(--red); color: var(--red); }
.stamp-btn .st-on, .stamp-btn .st-wait { display: none; }
/* 待复习：学会了 / 自己盖了章，还没经过复习检验——淡红虚线章 */
.pt.pending .stamp-btn { border: 2px dashed var(--red); color: var(--red); transform: rotate(-8deg); opacity: .8; }
.pt.pending .stamp-btn .st-off { display: none; }
.pt.pending .stamp-btn .st-wait { display: block; font-weight: 800; font-size: calc(14px * var(--fs)); }
.pt.pending .stamp-btn .st-wait small { display: block; font-weight: 600; font-size: calc(10.5px * var(--fs)); margin-top: 1px; }
.pi.rev { border-color: color-mix(in srgb, var(--red) 55%, var(--line)); border-style: dashed; color: var(--ink-2); }
.pi.rev::before { content: "◔ "; color: var(--red); }
.pi.half::before { content: "· "; color: var(--accent); font-weight: 900; }
.pt.mastered .stamp-btn { border: 3px double var(--red); color: var(--red); background: var(--red-soft); transform: rotate(-13deg); }
.pt.mastered .stamp-btn .st-off { display: none; }
.pt.mastered .stamp-btn .st-on { display: block; font-family: var(--f-display); font-weight: 900; font-size: calc(16px * var(--fs)); letter-spacing: .08em; }
.pt.mastered .stamp-btn .st-on small { display: block; font: 600 calc(9.5px * var(--fs)) var(--f-mono); letter-spacing: .06em; }
.pt.just .stamp-btn { animation: stamp .38s cubic-bezier(.2, 1.5, .4, 1); }
@keyframes stamp { 0% { transform: rotate(-13deg) scale(1.7); opacity: 0; } 100% { transform: rotate(-13deg) scale(1); opacity: 1; } }

.pt-key {
  margin: 20px 0 4px; padding: 12px 18px; border-radius: 8px; border: 1px solid var(--line-2);
  background-color: var(--card-2);
  background-image: linear-gradient(var(--grid) 1px, transparent 1px), linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 18px 18px; background-position: -1px -1px;
  display: flex; flex-wrap: wrap; justify-content: center; align-items: center; gap: 0 40px; position: relative;
}
.pt-key::before { content: "核心公式"; position: absolute; top: -9px; left: 14px; padding: 0 6px; font: 600 calc(11px * var(--fs))/18px var(--f-mono); letter-spacing: .1em; color: var(--accent); background: var(--card); }
.key-item { text-align: center; min-width: 0; max-width: 100%; overflow-x: auto; overflow-y: hidden; }
.key-item .katex-display { margin: .35em 0; }
.key-item .katex { font-size: 1.28em; }
.key-label { display: block; font-size: calc(12px * var(--fs)); color: var(--ink-3); margin-bottom: -4px; }

/* 卡片里的动画按原来的宽度画（约 876px，宽屏时整块居中），不跟着页面无限拉宽 */
.pt-anim { max-width: 878px; margin: 20px auto 6px; border: 1px solid var(--line); border-radius: 10px; background: var(--card-2); overflow: hidden; }
.pt-anim figcaption { display: flex; align-items: baseline; gap: 6px 10px; flex-wrap: wrap; padding: 10px 16px; border-bottom: 1px solid var(--line-2); font-size: calc(14.5px * var(--fs)); }
.live { font: 700 calc(10.5px * var(--fs)) var(--f-mono); letter-spacing: .12em; color: var(--accent); box-shadow: inset 0 0 0 1px var(--accent); border-radius: 3px; padding: 2px 6px; }
.pt-anim figcaption b { font-weight: 700; }
.hint { color: var(--ink-3); font-size: calc(13px * var(--fs)); flex-basis: 100%; }
@media (min-width: 720px) { .hint { flex-basis: auto; } }
.anim-host { min-height: 140px; position: relative; }
.anim-host.pending::after { content: "动画加载中…"; position: absolute; inset: 0; display: grid; place-items: center; color: var(--ink-3); font-size: calc(13px * var(--fs)); }
.anim-err { padding: 22px; color: var(--bad); font-size: calc(14px * var(--fs)); }

/* 工具包控件 */
.ma-stage { display: flex; flex-direction: column; }
.ma-canvas-wrap { position: relative; width: 100%; }
.ma-canvas { display: block; width: 100%; background: var(--card); -webkit-user-select: none; user-select: none; }
.ma-ui { display: flex; flex-wrap: wrap; align-items: center; gap: 10px 18px; padding: 12px 16px 14px; border-top: 1px solid var(--line-2); font-size: 14px; }
.ma-ui:empty { display: none; }
.ma-row { display: flex; flex-wrap: wrap; align-items: center; gap: 10px 18px; flex-basis: 100%; min-width: 0; }
.ma-slider { display: flex; align-items: center; gap: 10px; flex: 1 1 220px; max-width: 400px; min-width: 0; }
.ma-scrub .ma-slider { max-width: none; }
.ma-sl-name { font-size: 14px; color: var(--ink-2); white-space: nowrap; }
.ma-sl-name .katex { font-size: 1.05em; }
.ma-slider input[type="range"] { flex: 1; min-width: 70px; accent-color: var(--accent); height: 22px; }
.ma-sl-val { font: 600 13px var(--f-mono); color: var(--ink); min-width: 3.4em; text-align: right; font-variant-numeric: tabular-nums; }
.ma-btn { min-height: 32px; padding: 0 12px; border: 1px solid var(--line); border-radius: 6px; background: var(--card); color: var(--ink); font-size: 13px; font-weight: 600; white-space: nowrap; }
.ma-btn:hover:not(:disabled) { border-color: var(--ink-3); }
.ma-btn.primary { background: var(--accent); border-color: var(--accent); color: var(--on-accent); }
.ma-btn:disabled { opacity: .45; cursor: default; }
.ma-toggle { display: inline-flex; align-items: center; gap: 7px; cursor: pointer; font-size: 14px; color: var(--ink-2); }
.ma-toggle input { accent-color: var(--accent); width: 16px; height: 16px; }
.ma-select { display: inline-flex; align-items: center; gap: 8px; font-size: 14px; color: var(--ink-2); }
.ma-select select { height: 32px; border: 1px solid var(--line); border-radius: 6px; background: var(--card); padding: 0 8px; font-size: 13.5px; }
.ma-seg { display: inline-flex; border: 1px solid var(--line); border-radius: 7px; overflow: hidden; flex-wrap: wrap; }
.ma-seg button { border: 0; border-left: 1px solid var(--line); background: var(--card); padding: 5px 11px; font-size: 13px; color: var(--ink-2); }
.ma-seg button:first-child { border-left: 0; }
.ma-seg button.on { background: var(--accent); color: var(--on-accent); }
.ma-readout { flex-basis: 100%; font-size: 15px; color: var(--ink); line-height: 1.7; overflow-x: auto; overflow-y: hidden; }
.ma-readout .katex { font-size: 1.1em; }
.ma-note { flex-basis: 100%; font-size: 13px; color: var(--ink-3); }

/* 分节 */
.pt-sec { margin-top: 24px; }
.sec-h { font-size: calc(13px * var(--fs)); font-weight: 700; letter-spacing: .16em; color: var(--ink-3); margin: 0 0 8px; display: flex; align-items: center; gap: 10px; }
.sec-h::after { content: ""; flex: 1; height: 1px; background: var(--line-2); }
.sec-h .mini { order: 2; }
.mini { font-size: calc(12.5px * var(--fs)); font-weight: 600; letter-spacing: 0; padding: 3px 10px; border-radius: 999px; border: 1px solid var(--line); background: var(--card); color: var(--ink-2); }
.mini:hover { border-color: var(--accent); color: var(--accent); }
.prose { max-width: 46em; }
.prose p { margin: 0 0 .75em; }
.prose p:last-child { margin-bottom: 0; }
.prose ul, .prose ol { margin: .2em 0 .8em; padding-left: 1.4em; }
.prose li { margin: .25em 0; }
.prose b, .prose strong { font-weight: 700; color: var(--ink); }
.prose em { font-style: normal; background: linear-gradient(transparent 58%, var(--hl) 58%); }
.prose .hl, .hl { background: linear-gradient(transparent 58%, var(--hl) 58%); }
.prose .red, .red { color: var(--red); }
.prose small { color: var(--ink-3); }
.tbl-wrap { overflow-x: auto; margin: .5em 0 1em; }
.prose table, table.tbl { border-collapse: collapse; font-size: calc(14.5px * var(--fs)); line-height: 1.6; }
.prose th, .prose td, .tbl th, .tbl td { border: 1px solid var(--line); padding: 6px 12px; text-align: center; }
.prose th, .tbl th { background: var(--card-3); font-weight: 700; }

.steps { list-style: none; margin: 0; padding: 0; counter-reset: st; }
.step { position: relative; padding: 2px 0 12px 44px; counter-increment: st; transition: opacity .3s, filter .3s; }
.step::before { content: counter(st); position: absolute; left: 0; top: 8px; width: 27px; height: 27px; border-radius: 50%; box-shadow: inset 0 0 0 1.5px var(--accent); color: var(--accent); font: 700 calc(13px * var(--fs))/27px var(--f-mono); text-align: center; background: var(--card); z-index: 1; }
.step:not(:last-child)::after { content: ""; position: absolute; left: 13px; top: 36px; bottom: -4px; width: 1.5px; background: var(--line); }
.step-tex { overflow-x: auto; overflow-y: hidden; }
.step-tex .katex-display { margin: .3em 0; text-align: left; }
.step-tex .katex-display > .katex { text-align: left; }
.step-note { color: var(--ink-2); font-size: calc(14.5px * var(--fs)); line-height: 1.7; max-width: 46em; }
.steps-sec.stepping .step.future { opacity: .1; filter: blur(2px); }
.steps-sec.stepping .step.now::before { background: var(--accent); color: var(--on-accent); }
.step-ctl { display: inline-flex; gap: 6px; align-items: center; order: 2; }
.step-ctl .cnt { font: 600 calc(12px * var(--fs)) var(--f-mono); color: var(--ink-3); letter-spacing: 0; }

.pt-mn { margin-top: 24px; padding: 14px 20px 16px; border-radius: 8px; background: var(--note-bg); border: 1px dashed var(--note-line); }
.mn-label { font-size: calc(12.5px * var(--fs)); font-weight: 700; letter-spacing: .16em; color: var(--red); margin-bottom: 4px; }
.mn-body { font-family: var(--f-display); font-weight: 600; font-size: calc(17px * var(--fs)); line-height: 1.85; color: var(--note-ink); }
.mn-body p { margin: 0 0 .4em; }
.mn-body p:last-child { margin: 0; }
.mn-body b { font-weight: 900; }

.ex { border: 1px solid var(--line-2); border-radius: 8px; padding: 12px 16px; margin-top: 10px; background: var(--card); }
.ex-q { line-height: 1.8; }
.ex-tag { font: 700 calc(12px * var(--fs)) var(--f-mono); color: var(--accent); margin-right: 8px; }
.ex-a summary { cursor: pointer; color: var(--accent); font-size: calc(14px * var(--fs)); font-weight: 700; margin-top: 6px; list-style: none; width: fit-content; }
.ex-a summary::-webkit-details-marker { display: none; }
.ex-a summary::before { content: "▸ "; }
.ex-a[open] summary::before { content: "▾ "; }
.ex-a .prose { padding-top: 8px; border-top: 1px dashed var(--line); margin-top: 8px; }

.pitfalls { margin: 0; padding: 0; list-style: none; }
.pitfalls li { position: relative; padding-left: 26px; margin: 6px 0; line-height: 1.75; }
.pitfalls li::before { content: "✗"; position: absolute; left: 4px; top: 0; color: var(--red); font-weight: 900; }

.qz { margin-top: 12px; }
.qz + .qz { border-top: 1px dashed var(--line); padding-top: 14px; }
.qz-q { font-weight: 600; margin-bottom: 8px; line-height: 1.75; }
.qz-opts { display: grid; grid-template-columns: repeat(auto-fit, minmax(210px, 1fr)); gap: 8px; }
.qz-opt { position: relative; display: flex; align-items: center; gap: 10px; text-align: left; padding: 9px 42px 9px 12px; border: 1px solid var(--line); border-radius: 8px; background: var(--card); font-size: calc(15px * var(--fs)); line-height: 1.55; color: var(--ink); min-width: 0; }
.qz-opt:hover:not(:disabled) { border-color: var(--accent); }
.qz-opt:disabled { cursor: default; }
.qz-letter { font: 700 calc(12px * var(--fs)) var(--f-mono); color: var(--ink-3); flex: 0 0 auto; }
.qz-text { min-width: 0; overflow-x: auto; }
.qz-opt.right { border-color: var(--good); background: var(--good-soft); }
.qz-opt.wrong { border-color: var(--bad); background: var(--bad-soft); }
.qz-mark { position: absolute; right: 12px; top: 50%; transform: translateY(-50%) rotate(-8deg); font: 900 calc(24px * var(--fs))/1 var(--f-display); color: var(--red); }
.qz-opt.right .qz-mark::after { content: "✓"; }
.qz-opt.wrong .qz-mark::after { content: "✗"; }
.qz-why { margin-top: 8px; font-size: calc(14.5px * var(--fs)); color: var(--ink-2); padding: 10px 14px; background: var(--card-2); border-radius: 8px; border: 1px solid var(--line-2); }
.qz-why b.ok { color: var(--good); } .qz-why b.no { color: var(--bad); }

.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-top: 32px; }
.pager a { display: block; padding: 14px 18px; border: 1px solid var(--line); border-radius: 10px; background: var(--card); text-decoration: none; min-width: 0; }
.pager a:hover { border-color: var(--accent); }
.pager small { display: block; font: 600 calc(12px * var(--fs)) var(--f-mono); color: var(--ink-3); letter-spacing: .08em; }
.pager b { font-family: var(--f-display); font-weight: 900; font-size: calc(17px * var(--fs)); }
.pager .next { text-align: right; grid-column: 2; }

/* ---------- 公式速查 ---------- */
.sheet-head { margin-bottom: 18px; }
.sheet-head h2 { font-family: var(--f-display); font-weight: 900; font-size: clamp(28px, 3.6vw, 40px); margin: 0 0 8px; }
.sheet-head p { margin: 0 0 14px; color: var(--ink-2); }
.sheet-ch { margin-top: 28px; }
.sheet-ch h3 { font-family: var(--f-display); font-weight: 900; font-size: calc(20px * var(--fs)); margin: 0 0 12px; display: flex; align-items: baseline; gap: 10px; flex-wrap: wrap; }
.sheet-ch h3 small { font: 500 calc(12px * var(--fs)) var(--f-mono); color: var(--ink-3); }
.sheet-grid { columns: 290px; column-gap: 12px; }
.sheet-item { break-inside: avoid; display: block; margin: 0 0 12px; padding: 10px 14px 8px; background: var(--card); border: 1px solid var(--line); border-radius: 8px; text-decoration: none; }
.sheet-item:hover { border-color: var(--accent); }
.si-t { display: flex; justify-content: space-between; gap: 8px; font-size: calc(13.5px * var(--fs)); color: var(--ink-2); font-weight: 600; }
.si-t i { font-style: normal; font: 500 calc(11px * var(--fs)) var(--f-mono); color: var(--ink-3); white-space: nowrap; }
.si-f { display: block; overflow-x: auto; overflow-y: hidden; }
.si-f .katex-display { margin: .35em 0 .15em; }
.si-f.txt { font-size: calc(14px * var(--fs)); color: var(--ink); padding: 4px 0; }

/* ---------- 记忆卡片 ---------- */
.overlay {
  position: fixed; inset: 0; z-index: 100; display: flex; flex-direction: column; overflow: auto;
  background: color-mix(in srgb, var(--paper) 96%, transparent);
  -webkit-backdrop-filter: blur(6px); backdrop-filter: blur(6px);
  padding: calc(env(safe-area-inset-top, 0px) + 14px) 16px calc(env(safe-area-inset-bottom, 0px) + 18px);
}
.fc-top { width: 100%; max-width: 780px; margin: 0 auto; display: flex; align-items: center; gap: 10px 14px; flex-wrap: wrap; }
.fc-title { font-family: var(--f-display); font-weight: 900; font-size: calc(18px * var(--fs)); }
.fc-count { font: 600 calc(13px * var(--fs)) var(--f-mono); color: var(--ink-3); font-variant-numeric: tabular-nums; }
.fc-top .spacer { flex: 1; }
.fc-top select { height: 34px; border: 1px solid var(--line); border-radius: 8px; background: var(--card); padding: 0 8px; font-size: calc(13.5px * var(--fs)); }
.fc-bar { width: 100%; max-width: 780px; margin: 10px auto 0; }
.fc-stage { width: 100%; max-width: 780px; margin: 14px auto 0; perspective: 1600px; }
.fc-card { position: relative; display: grid; min-height: 380px; transition: transform .55s cubic-bezier(.3, .7, .3, 1); transform-style: preserve-3d; cursor: pointer; }
.fc-card.flipped { transform: rotateY(180deg); }
.fc-face { grid-area: 1 / 1; backface-visibility: hidden; -webkit-backface-visibility: hidden; background: var(--card); border: 1px solid var(--line); border-radius: 14px; padding: 26px 30px; box-shadow: var(--shadow); display: flex; flex-direction: column; gap: 12px; min-width: 0; overflow: hidden; }
.fc-back { transform: rotateY(180deg); }
.fc-face .fc-q { font-family: var(--f-display); font-weight: 900; font-size: clamp(26px, 4vw, 36px); line-height: 1.3; margin: auto 0 0; text-wrap: balance; }
.fc-face .fc-prompt { color: var(--ink-3); font-size: calc(15px * var(--fs)); margin: 0 0 auto; }
.fc-face .fc-meta { display: flex; gap: 6px; flex-wrap: wrap; align-items: center; font-size: calc(13px * var(--fs)); color: var(--ink-3); }
.fc-back .fc-key { overflow-x: auto; overflow-y: hidden; padding: 6px 12px; border-radius: 8px; background-color: var(--card-2); background-image: linear-gradient(var(--grid) 1px, transparent 1px), linear-gradient(90deg, var(--grid) 1px, transparent 1px); background-size: 18px 18px; }
.fc-back .fc-key .katex { font-size: 1.2em; }
.fc-back .fc-sum { font-size: calc(16px * var(--fs)); color: var(--ink); }
.fc-back .pt-mn { margin-top: 0; }
.fc-flip-hint { margin-top: auto; font-size: calc(12.5px * var(--fs)); color: var(--ink-3); text-align: center; }
.fc-actions { width: 100%; max-width: 780px; margin: 14px auto 0; display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; }
.fc-actions button { min-height: 50px; border-radius: 10px; border: 1px solid var(--line); background: var(--card); font-weight: 700; font-size: calc(15px * var(--fs)); }
.fc-actions button small { display: block; font: 500 calc(11px * var(--fs)) var(--f-mono); color: var(--ink-3); }
.fc-actions .r1:hover { border-color: var(--bad); color: var(--bad); }
.fc-actions .r2:hover { border-color: var(--c2); color: var(--c2); }
.fc-actions .r3 { border-color: var(--red); color: var(--red); }
.fc-actions .r3:hover { background: var(--red-soft); }
.fc-help { width: 100%; max-width: 780px; margin: 12px auto 0; text-align: center; font-size: calc(12.5px * var(--fs)); color: var(--ink-3); }
.fc-done { max-width: 560px; margin: 60px auto 0; text-align: center; }
.fc-done h3 { font-family: var(--f-display); font-weight: 900; font-size: calc(30px * var(--fs)); margin: 0 0 8px; }
.fc-done .seal-big { width: 120px; height: 120px; margin: 0 auto 18px; border-radius: 50%; border: 4px double var(--red); color: var(--red); display: grid; place-items: center; font-family: var(--f-display); font-weight: 900; font-size: calc(22px * var(--fs)); transform: rotate(-12deg); background: var(--red-soft); }
.fc-go { align-self: flex-start; }

/* ---------- 账号：用户菜单 ---------- */
.user-menu { position: relative; flex: 0 0 auto; }
.user-chip { display: inline-flex; align-items: center; gap: 8px; height: 38px; padding: 0 12px 0 4px; border: 1px solid var(--line); background: var(--card); border-radius: 999px; max-width: 170px; }
.user-chip:hover { border-color: var(--ink-3); }
.avatar { flex: 0 0 auto; width: 30px; height: 30px; border-radius: 6px; background: var(--red); color: var(--on-red); display: grid; place-items: center; font-family: var(--f-display); font-weight: 900; font-size: calc(16px * var(--fs)); line-height: 1; transform: rotate(-4deg); box-shadow: inset 0 0 0 1.5px var(--red), inset 0 0 0 2.5px var(--on-red); }
.avatar.big { width: 64px; height: 64px; border-radius: 10px; font-size: calc(34px * var(--fs)); box-shadow: inset 0 0 0 2.5px var(--red), inset 0 0 0 4.5px var(--on-red); }
.uname { font-size: calc(14px * var(--fs)); font-weight: 600; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.menu { position: absolute; right: 0; top: calc(100% + 8px); min-width: 200px; background: var(--card); border: 1px solid var(--line); border-radius: 10px; box-shadow: var(--shadow); padding: 6px; z-index: 70; }
.menu-head { padding: 8px 10px 10px; border-bottom: 1px solid var(--line-2); margin-bottom: 4px; display: flex; flex-direction: column; line-height: 1.4; }
.menu-head b { font-size: calc(15px * var(--fs)); }
.menu-head small { font-size: calc(12px * var(--fs)); color: var(--ink-3); }
.menu-item { display: block; width: 100%; text-align: left; padding: 9px 10px; border: 0; background: none; border-radius: 6px; font-size: calc(14.5px * var(--fs)); text-decoration: none; color: var(--ink); }
.menu-item:hover { background: var(--card-3); }

/* ---------- 登录 / 注册 ---------- */
.auth { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 420px); grid-template-areas: "pitch card"; gap: 32px 56px; align-items: start; padding-block: 24px 8px; }
.auth-card { grid-area: card; background: var(--card); border: 1px solid var(--line); border-radius: 14px; box-shadow: var(--shadow); padding: 8px 26px 26px; position: sticky; top: calc(var(--top-h) + 20px); }
.auth-pitch { grid-area: pitch; min-width: 0; }
.auth-pitch h1 { font-family: var(--f-display); font-weight: 900; font-size: clamp(34px, 4.6vw, 56px); line-height: 1.14; margin: 0; text-wrap: balance; }
.auth-pitch h1 em { font-style: normal; color: var(--red); background: linear-gradient(transparent 78%, var(--red-soft) 78%); }
.auth-pitch .hero-demo { margin-top: 26px; max-width: 560px; }
.auth-tabs { display: flex; gap: 22px; border-bottom: 1px solid var(--line-2); margin: 0 -2px 18px; }
.auth-tabs a { position: relative; padding: 14px 2px 12px; text-decoration: none; font-family: var(--f-display); font-weight: 900; font-size: calc(18px * var(--fs)); color: var(--ink-3); }
.auth-tabs a.on { color: var(--ink); }
.auth-tabs a.on::after { content: ""; position: absolute; left: 0; right: 0; bottom: -1px; height: 3px; border-radius: 2px; background: var(--red); }
.auth-form { display: flex; flex-direction: column; gap: 14px; }
.auth-form h4 { margin: 0; font-size: calc(15px * var(--fs)); }
.field { display: flex; flex-direction: column; gap: 6px; }
.field > span { font-size: calc(14px * var(--fs)); font-weight: 600; color: var(--ink-2); }
.field > span em { font-style: normal; font-weight: 400; font-size: calc(12px * var(--fs)); color: var(--ink-3); margin-left: 4px; }
.field input, .field select { height: 44px; border: 1px solid var(--line); border-radius: 8px; background: var(--card-2); padding: 0 12px; font-size: calc(15px * var(--fs)); color: var(--ink); width: 100%; min-width: 0; }
.field input:focus, .field select:focus { outline: 2px solid var(--accent); outline-offset: 0; border-color: transparent; background: var(--card); }
.field small { font-size: calc(12.5px * var(--fs)); color: var(--ink-3); line-height: 1.5; }
.check { display: inline-flex; align-items: center; gap: 8px; font-size: calc(14px * var(--fs)); color: var(--ink-2); cursor: pointer; }
.check input { width: 16px; height: 16px; accent-color: var(--red); }
.form-err { margin: 0; padding: 10px 12px; border-radius: 8px; background: var(--bad-soft); color: var(--bad); font-size: calc(14px * var(--fs)); line-height: 1.6; border: 1px solid color-mix(in srgb, var(--bad) 30%, transparent); }
.form-note { margin: 0 0 14px; padding: 10px 12px; border-radius: 8px; background: var(--note-bg); border: 1px dashed var(--note-line); font-size: calc(14px * var(--fs)); color: var(--note-ink); }
.form-alt { margin: 2px 0 0; font-size: calc(14px * var(--fs)); color: var(--ink-3); text-align: center; }
.form-alt a { color: var(--red); font-weight: 600; }
.btn.block { width: 100%; min-height: 46px; font-size: calc(16px * var(--fs)); }
.btn.primary:disabled { opacity: .6; cursor: default; filter: none; }

/* ---------- 我的学习 ---------- */
.me { max-width: 980px; }
.me-head { display: flex; align-items: center; gap: 18px; }
.me-title { font-family: var(--f-display); font-weight: 900; font-size: clamp(26px, 3.4vw, 36px); line-height: 1.25; margin: 0 0 4px; }
.me-sub { margin: 0; color: var(--ink-3); font-size: calc(14px * var(--fs)); }
.me-loading { color: var(--ink-3); }
.me-stats { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 12px; margin-top: 24px; }
.stat { background: var(--card); border: 1px solid var(--line); border-radius: 10px; padding: 14px 16px 12px; display: flex; flex-direction: column; gap: 2px; min-width: 0; }
.stat b { font: 700 calc(30px * var(--fs))/1.1 var(--f-mono); font-variant-numeric: tabular-nums; color: var(--ink); }
.stat span { font-size: calc(14px * var(--fs)); color: var(--ink-2); font-weight: 600; }
.stat small { display: block; font-weight: 400; font-size: calc(12.5px * var(--fs)); color: var(--ink-3); }
.me-block { margin-top: 18px; background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 18px 20px 20px; }
.me-block h3 { font-family: var(--f-display); font-weight: 900; font-size: calc(18px * var(--fs)); margin: 0 0 12px; }
.me-stage { display: grid; grid-template-columns: 56px minmax(0, 1fr) 64px auto; align-items: center; gap: 12px; padding: 8px 0; border-top: 1px dashed var(--line-2); }
.me-stage:first-of-type { border-top: 0; }
.me-sn { font-family: var(--f-brush); font-size: calc(26px * var(--fs)); line-height: 1; color: var(--accent); }
.me-stage .prog-bar { height: 8px; border-radius: 4px; }
.me-stage .prog-bar i { background: var(--accent); }
.me-sc { font: 600 calc(13px * var(--fs)) var(--f-mono); color: var(--ink-2); text-align: right; font-variant-numeric: tabular-nums; }
.me-chart { display: grid; grid-template-columns: repeat(30, minmax(0, 1fr)); align-items: end; gap: 3px; height: 120px; padding: 6px 0 0; border-bottom: 1px solid var(--line); }
.me-chart .bar { height: 100%; display: flex; align-items: flex-end; }
.me-chart .bar i { display: block; width: 100%; border-radius: 3px 3px 0 0; background: color-mix(in srgb, var(--red) 55%, transparent); }
.me-chart .bar.cur i { background: var(--red); }
.me-axis { display: flex; justify-content: space-between; font: 500 calc(11.5px * var(--fs)) var(--f-mono); color: var(--ink-3); margin-top: 6px; }
.me-note { margin: 10px 0 0; font-size: calc(13px * var(--fs)); color: var(--ink-3); }
.me-forms { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px 28px; margin-bottom: 16px; }
.me-forms .btn { align-self: flex-start; }

/* ---------- 教学模式 ---------- */
.learn-btn { display: inline-flex; align-items: center; gap: 8px; margin-top: 12px; padding: 5px 14px 5px 5px; border-radius: 999px; background: var(--card); box-shadow: inset 0 0 0 1.5px var(--accent); color: var(--accent); font-weight: 700; font-size: calc(14.5px * var(--fs)); text-decoration: none; transition: background .15s; }
.learn-btn:hover { background: color-mix(in srgb, var(--accent) 10%, var(--card)); }
.learn-btn small { font-weight: 500; font-size: calc(12px * var(--fs)); color: var(--ink-3); margin-left: 2px; }
.lb-ic { width: 26px; height: 26px; border-radius: 50%; background: var(--accent); color: var(--on-accent); display: grid; place-items: center; font-family: var(--f-display); font-weight: 900; font-size: calc(14px * var(--fs)); }
.today-learn { margin-top: 10px; }

.lesson { max-width: 980px; margin: 0 auto; }
.ls-top { display: flex; align-items: center; gap: 10px 16px; flex-wrap: wrap; }
.ls-exit { font-size: calc(14px * var(--fs)); color: var(--ink-2); text-decoration: none; white-space: nowrap; }
.ls-exit:hover { color: var(--ink); }
.ls-title { display: flex; align-items: center; gap: 8px; flex: 1 1 260px; min-width: 0; flex-wrap: wrap; }
.ls-title b { font-family: var(--f-display); font-weight: 900; font-size: clamp(19px, 2.4vw, 24px); line-height: 1.3; }
.ls-voice { display: inline-flex; align-items: center; gap: 6px; height: 36px; padding: 0 12px; border-radius: 999px; border: 1px solid var(--line); background: var(--card); color: var(--ink-2); font-size: calc(13.5px * var(--fs)); font-weight: 600; }
.ls-voice[aria-pressed="true"] { background: var(--accent); border-color: var(--accent); color: var(--on-accent); }
.ls-vbox { display: inline-flex; align-items: center; gap: 6px; }
.ls-vset { display: inline-flex; align-items: center; gap: 5px; height: 36px; padding: 0 11px; border-radius: 999px; border: 1px solid var(--line); background: var(--card); color: var(--ink-2); font-size: calc(13.5px * var(--fs)); font-weight: 600; }
.ls-vset[aria-expanded="true"] { border-color: var(--accent); color: var(--accent); }
.ls-vpanel { margin-top: 12px; padding: 12px 16px; border: 1px solid var(--line); border-radius: 12px; background: var(--card); box-shadow: var(--shadow); display: flex; flex-direction: column; gap: 10px; }
.ls-vrow { display: flex; align-items: center; gap: 8px 10px; flex-wrap: wrap; font-size: calc(14.5px * var(--fs)); }
.ls-vrow > span { color: var(--ink-3); font-weight: 700; font-size: calc(13.5px * var(--fs)); min-width: 2.6em; }
.ls-vrow select { height: 36px; flex: 1 1 220px; min-width: 0; max-width: 380px; border: 1px solid var(--line); border-radius: 8px; background: var(--card-2); color: var(--ink); padding: 0 8px; font-size: calc(14.5px * var(--fs)); }
.ls-vrate button[data-rate] { height: 32px; padding: 0 12px; border-radius: 999px; border: 1px solid var(--line); background: var(--card-2); color: var(--ink-2); font-size: calc(13.5px * var(--fs)); }
.ls-vrate button[data-rate][aria-pressed="true"] { background: var(--accent); border-color: var(--accent); color: var(--on-accent); font-weight: 700; }
.ls-vtry { display: inline-flex; align-items: center; gap: 5px; margin-left: 4px; }
.ls-vtip { margin: 0; font-size: calc(13.5px * var(--fs)); line-height: 1.7; color: var(--ink-3); }
.ls-vtip b { color: var(--ink-2); }
.ls-parts { display: flex; align-items: center; gap: 4px 6px; margin-top: 14px; overflow-x: auto; scrollbar-width: none; padding-bottom: 2px; scroll-margin-top: calc(var(--top-h) + 12px); }
.ls-parts::-webkit-scrollbar { display: none; }
.ls-parts .lp { font-size: calc(13px * var(--fs)); white-space: nowrap; color: var(--ink-3); padding: 3px 9px; border-radius: 999px; }
.ls-parts .lp.done { color: var(--ink-2); }
.ls-parts .lp.done::before { content: "✓ "; color: var(--red); font-weight: 700; }
.ls-parts .lp.on { background: var(--accent); color: var(--on-accent); font-weight: 700; }
.ls-parts i { font-style: normal; color: var(--line); }
.ls-bar { height: 4px; border-radius: 2px; background: var(--card-3); margin-top: 10px; overflow: hidden; }
.ls-bar i { display: block; height: 100%; width: 0; background: var(--accent); transition: width .35s; }
.ls-stage { min-height: 52vh; padding-top: 18px; }
.ls-step { display: flex; flex-direction: column; gap: 16px; animation: lsIn .35s ease-out; }
@keyframes lsIn { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: none; } }
.ls-teacher { display: flex; align-items: flex-start; gap: 14px; }
.ls-avatar { flex: 0 0 auto; width: 52px; height: 52px; border-radius: 9px; background: var(--red); color: var(--on-red); display: grid; place-items: center; font-family: var(--f-display); font-weight: 900; font-size: calc(28px * var(--fs)); transform: rotate(-4deg); box-shadow: inset 0 0 0 2px var(--red), inset 0 0 0 3.5px var(--on-red); margin-top: 4px; }
.ls-bubble { position: relative; flex: 1; min-width: 0; background: var(--card); border: 1px solid var(--line); border-radius: 14px; padding: 12px 20px 16px; box-shadow: var(--shadow); }
.ls-bubble::before { content: ""; position: absolute; left: -8px; top: 22px; width: 14px; height: 14px; background: var(--card); border-left: 1px solid var(--line); border-bottom: 1px solid var(--line); transform: rotate(45deg); }
.ls-part { display: inline-block; font-size: calc(12.5px * var(--fs)); font-weight: 700; letter-spacing: .08em; color: var(--accent); margin-bottom: 4px; }
.ls-say { font-size: calc(18px * var(--fs)); line-height: 1.9; color: var(--ink); }
.ls-say p { margin: 0 0 .5em; }
.ls-say p:last-child { margin: 0; }
.ls-say .katex { font-size: 1.06em; }
.ls-more-btn { margin-top: 10px; }
.ls-more { margin-top: 10px; padding: 12px 14px; border-radius: 10px; background: var(--note-bg); border: 1px dashed var(--note-line); color: var(--note-ink); font-size: calc(16px * var(--fs)); line-height: 1.85; }
.ls-board { background-color: var(--card-2); background-image: linear-gradient(var(--grid) 1px, transparent 1px), linear-gradient(90deg, var(--grid) 1px, transparent 1px); background-size: 22px 22px; border: 1px solid var(--line); border-radius: 12px; padding: 20px 22px; display: flex; flex-direction: column; gap: 14px; min-width: 0; }
.ls-board-in { font-size: calc(17px * var(--fs)); line-height: 1.85; overflow-x: auto; overflow-y: hidden; }
.ls-board-in .katex-display { margin: .4em 0; }
.ls-board-in .katex-display > .katex { font-size: 1.28em; }
.ls-board-in p { margin: 0 0 .6em; }
.ls-board-in small { display: block; color: var(--ink-3); font-size: calc(13px * var(--fs)); }
.ls-mn { font-family: var(--f-display); font-weight: 600; font-size: calc(18px * var(--fs)); color: var(--note-ink); }
.ls-board.split { display: grid; gap: 16px; align-items: start; }
.ls-col { display: flex; flex-direction: column; gap: 14px; min-width: 0; }
/* 动画一栏约 480px：卡片动画按窄版画（课件里“动手做”的描述都按这个样子写、截图核对过），不要随意加宽 */
@media (min-width: 900px) { .ls-board.split { grid-template-columns: minmax(0, 1.12fr) minmax(0, 1fr); } }
/* 宽屏：动画那一栏固定 485px（课件里“动手做”按这个宽度写的，别加宽），其余空间都给题目 / 板书 */
@media (min-width: 1000px) { .ls-board.split { grid-template-columns: 485px minmax(0, 1fr); } }
.ls-board > .ls-anim, .ls-board > .ls-task { width: 100%; max-width: 934px; align-self: center; }
.ls-lines .ln, .lq, .ls-pq { scroll-margin-bottom: 96px; scroll-margin-top: calc(var(--top-h) + 12px); }
.ls-anim { border: 1px solid var(--line); border-radius: 10px; overflow: hidden; background: var(--card); min-height: 160px; }
.ls-task { margin: 0; padding: 10px 14px; border-radius: 8px; background: var(--card); border: 1px solid var(--line-2); font-size: calc(15.5px * var(--fs)); }
.ls-task b { color: var(--accent); }
.ls-ex { font-size: calc(17px * var(--fs)); line-height: 1.85; padding: 12px 16px; background: var(--card); border-radius: 10px; border: 1px solid var(--line-2); }
.ls-lines { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: 10px; }
.ls-lines .ln { padding: 8px 14px 10px; border-left: 3px solid var(--accent); background: var(--card); border-radius: 0 8px 8px 0; min-width: 0; }
.ls-lines .ln.fresh { animation: lnIn .45s ease-out; }
@keyframes lnIn { from { opacity: 0; transform: translateX(-10px); } to { opacity: 1; transform: none; } }
.ls-lines .ln-ask { border-left-color: var(--red); background: transparent; padding: 0 0 0 14px; }
.ln-tex { overflow-x: auto; overflow-y: hidden; }
.ln-tex .katex-display { margin: .2em 0; text-align: left; }
.ln-tex .katex-display > .katex { text-align: left; font-size: 1.18em; }
.ln-say { font-size: calc(15.5px * var(--fs)); color: var(--ink-2); line-height: 1.75; }
.ls-pq-h { display: flex; align-items: center; justify-content: space-between; gap: 10px; font-size: calc(13.5px * var(--fs)); font-weight: 700; color: var(--ink-3); margin-bottom: 8px; }
.ls-dots { display: inline-flex; gap: 7px; }
.ls-dots i { width: 11px; height: 11px; border-radius: 50%; background: var(--card); box-shadow: inset 0 0 0 1.5px var(--line); }
.ls-dots i.cur { box-shadow: inset 0 0 0 1.5px var(--accent), 0 0 0 2px color-mix(in srgb, var(--accent) 30%, transparent); }
.ls-dots i.r { background: var(--good); box-shadow: none; }
.ls-dots i.s { background: var(--note-line); box-shadow: none; }
.ls-pq-h .lvl { color: var(--accent); }
.ls-list { margin: 0; padding-left: 1.3em; font-size: calc(16.5px * var(--fs)); line-height: 1.85; }
.ls-list.tick { list-style: none; padding-left: 0; }
.ls-list.tick li { position: relative; padding-left: 26px; }
.ls-list.tick li + li { margin-top: 4px; }
.ls-list.tick li::before { content: "✓"; position: absolute; left: 2px; top: 0; color: var(--red); font-weight: 900; }
.ls-goal h4 { margin: 0 0 6px; font-size: calc(15px * var(--fs)); color: var(--ink-2); }
.ls-goal .ls-list + h4 { margin-top: 14px; }
.ls-howto { margin: 14px 0 0; font-size: calc(14.5px * var(--fs)); color: var(--ink-3); }
.ls-resume { margin-top: 14px; display: flex; align-items: center; gap: 10px; flex-wrap: wrap; padding: 10px 14px; border-radius: 10px; background: var(--note-bg); border: 1px dashed var(--note-line); color: var(--note-ink); font-size: calc(15px * var(--fs)); }
.ls-resume.top { margin: 0 0 16px; }
.ls-ask { display: flex; flex-direction: column; }
.lq { background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 14px 16px; box-shadow: var(--shadow); }
.ls-board .lq { box-shadow: none; }
.lq-q { font-size: calc(17px * var(--fs)); font-weight: 600; line-height: 1.8; margin-bottom: 10px; }
.lq-q::before { content: "问"; display: inline-grid; place-items: center; width: 24px; height: 24px; margin-right: 8px; border-radius: 6px; background: var(--red); color: var(--on-red); font-family: var(--f-display); font-weight: 900; font-size: calc(14px * var(--fs)); vertical-align: 2px; }
.lq-opts { display: grid; grid-template-columns: repeat(auto-fit, minmax(210px, 1fr)); gap: 8px; }
.lq-opts.judge { grid-template-columns: repeat(2, minmax(0, 160px)); }
.lq-opt { position: relative; display: flex; align-items: center; gap: 10px; text-align: left; padding: 10px 40px 10px 12px; border: 1.5px solid var(--line); border-radius: 10px; background: var(--card-2); font-size: calc(16px * var(--fs)); line-height: 1.55; color: var(--ink); min-width: 0; }
.lq-opts.judge .lq-opt { justify-content: center; padding: 12px 20px; font-weight: 700; font-size: calc(17px * var(--fs)); }
.lq-opt:hover:not(:disabled) { border-color: var(--accent); background: var(--card); }
.lq-opt:disabled { cursor: default; }
.lq-l { font: 700 calc(12px * var(--fs)) var(--f-mono); color: var(--ink-3); }
.lq-t { min-width: 0; overflow-x: auto; }
.lq-opt.right { border-color: var(--good); background: var(--good-soft); }
.lq-opt.wrong { border-color: var(--bad); background: var(--bad-soft); opacity: .8; }
.lq-mk { position: absolute; right: 12px; top: 50%; transform: translateY(-50%) rotate(-8deg); font: 900 calc(24px * var(--fs))/1 var(--f-display); color: var(--red); }
.lq-opt.right .lq-mk::after { content: "✓"; }
.lq-opt.wrong .lq-mk::after { content: "✗"; }
.lq-input { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.lq-input input { height: 44px; width: min(240px, 100%); border: 1.5px solid var(--line); border-radius: 10px; background: var(--card-2); padding: 0 12px; font-size: calc(17px * var(--fs)); font-family: var(--f-mono); color: var(--ink); }
.lq-input input:focus { outline: 2px solid var(--accent); outline-offset: 0; border-color: transparent; }
.lq-unit { font-size: calc(16px * var(--fs)); color: var(--ink-2); }
.lq-tools { display: flex; gap: 8px; margin-top: 10px; flex-wrap: wrap; }
.lq-tools:empty { display: none; }
.lq-fb { margin-top: 10px; padding: 10px 14px; border-radius: 10px; font-size: calc(15.5px * var(--fs)); line-height: 1.8; }
.lq-fb.ok { background: var(--good-soft); border: 1px solid color-mix(in srgb, var(--good) 35%, transparent); }
.lq-fb.ok b { color: var(--good); }
.lq-fb.no { background: var(--bad-soft); border: 1px solid color-mix(in srgb, var(--bad) 30%, transparent); }
.lq-fb.no b { color: var(--bad); }
.lq-fb.hint { background: var(--note-bg); border: 1px dashed var(--note-line); color: var(--note-ink); }
.lq-fb.show { background: var(--card-2); border: 1px solid var(--line); }
.lq-fb.show b { color: var(--red); }
.lq.done .lq-tools { display: none; }
.ls-nav { position: sticky; bottom: 0; z-index: 20; display: flex; align-items: center; gap: 12px; margin-top: 22px; padding: 12px 0 calc(env(safe-area-inset-bottom, 0px) + 12px); background: color-mix(in srgb, var(--paper) 92%, transparent); -webkit-backdrop-filter: blur(8px); backdrop-filter: blur(8px); border-top: 1px solid var(--line); }
.ls-nav .btn { min-height: 48px; }
.ls-nav .btn.primary { flex: 1 1 auto; max-width: 360px; margin-left: auto; font-size: calc(16.5px * var(--fs)); }
.ls-nav .btn:disabled { opacity: .55; cursor: default; }
.ls-count { font: 600 calc(13px * var(--fs)) var(--f-mono); color: var(--ink-3); font-variant-numeric: tabular-nums; }
.ls-finish { text-align: center; padding: 30px 12px 10px; animation: lsIn .4s ease-out; }
.ls-finish h2 { font-family: var(--f-display); font-weight: 900; font-size: clamp(26px, 3.6vw, 36px); margin: 0 0 10px; }
.ls-finish p { max-width: 34em; margin: 0 auto; color: var(--ink-2); font-size: calc(16.5px * var(--fs)); line-height: 1.85; }
.ls-seal { width: 128px; height: 128px; margin: 0 auto 20px; border-radius: 50%; border: 4px double var(--red); color: var(--red); display: grid; place-items: center; font-family: var(--f-display); font-weight: 900; font-size: calc(26px * var(--fs)); line-height: 1.2; transform: rotate(-12deg); background: var(--red-soft); animation: stamp .45s cubic-bezier(.2, 1.5, .4, 1); }
.ls-review { max-width: 36em; margin: 18px auto 0; padding: 12px 16px; border-radius: 12px; background: var(--note-bg); border: 1px dashed var(--note-line); text-align: left; }
.ls-review h4 { margin: 0 0 8px; font-size: calc(14.5px * var(--fs)); color: var(--note-ink); }
.ls-review-list { display: flex; flex-wrap: wrap; gap: 8px; }
.ch-learn { margin-top: 14px; }
.ls-actions { display: flex; gap: 10px; justify-content: center; flex-wrap: wrap; margin-top: 22px; }
.ls-mk-note { margin: 10px 0 0 !important; font-size: calc(14px * var(--fs)) !important; color: var(--note-ink) !important; text-align: left; }
.ls-mk-note a { color: var(--red); font-weight: 700; }

/* ---------- 学习路径：前置知识 · 复习 · 错题本 ---------- */
/* 知识点状态色：已掌握 = 红；待复习 / 要巩固 = 红虚线；学了一半 = 墨色点；没学 = 灰 */
.s-mastered { --sc: var(--red); }
.s-review, .s-weak { --sc: color-mix(in srgb, var(--red) 60%, var(--ink-3)); }
.s-learning { --sc: var(--accent); }
.s-new { --sc: var(--ink-3); }
.pt-pre { display: flex; flex-wrap: wrap; align-items: center; gap: 6px; margin: 10px 0 0; font-size: calc(13px * var(--fs)); }
.pt-pre-l { color: var(--ink-3); font-weight: 600; margin-right: 2px; }
.pt-pre a { padding: 2px 9px; border-radius: 999px; border: 1px solid var(--line); background: var(--card-2); color: var(--ink-2); text-decoration: none; line-height: 1.6; }
.pt-pre a::before { content: ""; display: inline-block; width: 7px; height: 7px; margin-right: 6px; border-radius: 50%; border: 1.5px solid var(--sc); vertical-align: 1px; }
.pt-pre a.s-mastered::before { background: var(--sc); }
.pt-pre a.s-review::before, .pt-pre a.s-weak::before { border-style: dashed; }
.pt-pre a:hover { border-color: var(--ink-3); color: var(--ink); }
.pt-pre .katex { font-size: 1em; }

.ls-pre { margin-top: 16px; padding: 12px 16px 14px; border-radius: 12px; background: var(--card); border: 1px solid var(--line); }
.ls-pre h4 { margin: 0 0 8px; }
.ls-pre-list { display: flex; flex-wrap: wrap; gap: 8px; }
.ls-pre-i { display: inline-flex; align-items: baseline; gap: 6px; padding: 5px 12px; border-radius: 10px; border: 1.5px solid var(--sc); background: var(--card-2); color: var(--ink); text-decoration: none; font-size: calc(15px * var(--fs)); }
.ls-pre-i.s-review, .ls-pre-i.s-weak { border-style: dashed; }
.ls-pre-i.s-new { border-color: var(--line); }
.ls-pre-i small { font-size: calc(12px * var(--fs)); font-weight: 700; color: var(--sc); }
.ls-pre-i:hover { background: var(--card); }
.ls-pre-i .katex { font-size: 1em; }
.ls-pre-tip { margin: 10px 0 0; font-size: calc(14.5px * var(--fs)); line-height: 1.75; color: var(--ink-2); }
.ls-pre-tip.ok { color: var(--good); font-weight: 600; }
#lsPreQ { margin-top: 10px; display: flex; flex-direction: column; gap: 12px; }
#lsPreQ > .btn { align-self: flex-start; }
.ls-pre-h { font-size: calc(13px * var(--fs)); font-weight: 700; color: var(--ink-3); margin-bottom: 6px; }
.ls-pre-q .lq { box-shadow: none; background: var(--card-2); }
.ls-pre-res { padding: 10px 14px; border-radius: 10px; font-size: calc(15px * var(--fs)); line-height: 1.8; }
.ls-pre-res.ok { background: var(--good-soft); border: 1px solid color-mix(in srgb, var(--good) 35%, transparent); }
.ls-pre-res.ok b { color: var(--good); }
.ls-pre-res.no { background: var(--note-bg); border: 1px dashed var(--note-line); color: var(--note-ink); }
.ls-pre-res.no a { color: var(--red); font-weight: 700; }

#topReview { position: relative; text-decoration: none; }
.badge { position: absolute; top: -7px; right: -7px; min-width: 19px; height: 19px; padding: 0 5px; border-radius: 10px; background: var(--red); color: var(--on-red); font: 700 calc(11px * var(--fs))/19px var(--f-mono); text-align: center; box-shadow: 0 0 0 2px var(--paper); }

.plan { margin-top: 40px; }
.plan-head { display: flex; justify-content: space-between; align-items: baseline; gap: 6px 12px; flex-wrap: wrap; margin-bottom: 12px; }
.plan-head h2 { font-family: var(--f-display); font-weight: 900; font-size: calc(24px * var(--fs)); margin: 0; }
.plan-head p { margin: 0; color: var(--ink-3); font-size: calc(14px * var(--fs)); }
.plan-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 12px; }
.plan-card { display: flex; flex-direction: column; align-items: flex-start; gap: 10px; background: var(--card); border: 1px solid var(--line); border-radius: 10px; padding: 16px 18px 18px; min-width: 0; }
.plan-card.hot { border-color: var(--red); box-shadow: inset 0 0 0 1px var(--red); }
.plan-card h3 { display: flex; align-items: center; gap: 8px; font-family: var(--f-display); font-weight: 900; font-size: calc(18px * var(--fs)); margin: 0; }
.plan-card h3 span { display: inline-grid; place-items: center; width: 22px; height: 22px; border-radius: 50%; background: var(--red); color: var(--on-red); font: 700 calc(12.5px * var(--fs))/1 var(--f-mono); }
.plan-card p { margin: 0; color: var(--ink-2); font-size: calc(14.5px * var(--fs)); line-height: 1.75; }
.plan-card p b { color: var(--ink); }
.plan-card p small { display: block; color: var(--ink-3); font-size: calc(12.5px * var(--fs)); }
.plan-card .btn { margin-top: auto; }
.plan-tip { font-size: calc(13.5px * var(--fs)) !important; padding: 8px 10px; border-radius: 8px; background: var(--note-bg); border: 1px dashed var(--note-line); color: var(--note-ink) !important; }
.plan-tip a { color: var(--red); font-weight: 600; text-decoration: none; }
.plan-tip a:hover { text-decoration: underline; }

.rv, .mk { max-width: 860px; margin: 0 auto; }
.rv-top { display: flex; align-items: center; gap: 10px 16px; flex-wrap: wrap; }
.rv-title { font-family: var(--f-display); font-weight: 900; font-size: clamp(19px, 2.4vw, 24px); }
.rv-n { margin-left: auto; font: 600 calc(13px * var(--fs)) var(--f-mono); color: var(--ink-3); font-variant-numeric: tabular-nums; }
.rv-pt { display: flex; align-items: center; gap: 8px 10px; flex-wrap: wrap; margin: 18px 0 12px; font-size: calc(16px * var(--fs)); }
.rv-pt b { font-family: var(--f-display); font-weight: 900; }
.rv-link { margin-left: auto; font-size: calc(13.5px * var(--fs)); color: var(--ink-3); }
.rv-link:hover { color: var(--ink); }
.rv-say { margin: 0 0 12px; padding: 10px 14px; border-radius: 10px; background: var(--card); border: 1px solid var(--line-2); font-size: calc(15.5px * var(--fs)); line-height: 1.8; color: var(--ink-2); }
.rv .ls-board, .rv .ls-ex, .rv-lines { margin-bottom: 12px; }
.rv-q { min-height: 120px; }
.rv-tip { font-size: calc(13px * var(--fs)); color: var(--ink-3); }
.rv-finish .ls-actions { margin-top: 18px; }
.rv-list { list-style: none; max-width: 36em; margin: 18px auto 0; padding: 0; text-align: left; display: flex; flex-direction: column; gap: 8px; }
.rv-list li { display: flex; align-items: center; gap: 10px; padding: 10px 14px; border-radius: 10px; background: var(--card); border: 1px solid var(--line); }
.rv-list li.ok { border-color: color-mix(in srgb, var(--good) 45%, var(--line)); }
.rv-list li.no { border-style: dashed; border-color: color-mix(in srgb, var(--red) 50%, var(--line)); }
.rv-mark { font: 900 calc(20px * var(--fs))/1 var(--f-display); color: var(--good); }
.rv-list li.no .rv-mark { color: var(--red); }
.rv-t { flex: 1; min-width: 0; font-weight: 600; }
.rv-t small { display: block; font-weight: 400; font-size: calc(12.5px * var(--fs)); color: var(--ink-3); }
.rv-s { font: 600 calc(13px * var(--fs)) var(--f-mono); color: var(--ink-3); }
.mk-head h2 { font-family: var(--f-display); font-weight: 900; font-size: clamp(24px, 3.2vw, 32px); margin: 0 0 8px; }
.mk-head p { margin: 0 0 14px; color: var(--ink-2); font-size: calc(15px * var(--fs)); line-height: 1.8; }
.mk-pt { margin-top: 18px; background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 14px 18px 16px; }
.mk-pt h3 { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; margin: 0 0 10px; font-size: calc(17px * var(--fs)); }
.mk-pt h3 a { font-family: var(--f-display); font-weight: 900; color: var(--ink); text-decoration: none; }
.mk-pt h3 a:hover { text-decoration: underline; }
.mk-pt h3 small { margin-left: auto; font-size: calc(12.5px * var(--fs)); font-weight: 500; color: var(--ink-3); }
.mk-list { margin: 0; padding-left: 1.4em; display: flex; flex-direction: column; gap: 8px; }
.mk-list li { font-size: calc(15px * var(--fs)); line-height: 1.75; }
.mk-list li small { display: block; font-size: calc(12.5px * var(--fs)); color: var(--ink-3); }
.mk-list li small a { color: var(--red); }
.mk-q { overflow-x: auto; overflow-y: hidden; }
.mk-acts { display: flex; gap: 8px; flex-wrap: wrap; margin-top: 12px; }
.me-plan-row { display: flex; align-items: center; justify-content: space-between; gap: 8px 12px; flex-wrap: wrap; padding: 8px 0; border-top: 1px dashed var(--line-2); font-size: calc(15px * var(--fs)); color: var(--ink-2); }
.me-plan-row:first-of-type { border-top: 0; }
.me-plan-row b { font-family: var(--f-mono); color: var(--ink); }

/* ---------- 加载、提示 ---------- */
.ch-loading { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; margin-top: 22px; padding: 28px; border: 1px dashed var(--line); border-radius: 12px; background: var(--card); color: var(--ink-2); }
.spin { width: 18px; height: 18px; border-radius: 50%; border: 2.5px solid var(--line); border-top-color: var(--accent); animation: spin .8s linear infinite; }
@keyframes spin { to { transform: rotate(360deg); } }
.boot-err { max-width: 460px; margin: 12vh auto; padding: 0 20px; text-align: center; }
.boot-err .seal { margin: 0 auto 16px; width: 52px; height: 52px; font-size: calc(36px * var(--fs)); }
.boot-err h2 { font-family: var(--f-display); font-weight: 900; margin: 0 0 8px; }
.boot-err p { color: var(--ink-2); }
.toasts { position: fixed; left: 50%; bottom: calc(env(safe-area-inset-bottom, 0px) + 20px); transform: translateX(-50%); z-index: 200; display: flex; flex-direction: column; gap: 8px; align-items: center; pointer-events: none; width: max-content; max-width: calc(100vw - 32px); }
.toast { background: var(--ink); color: var(--card); padding: 10px 16px; border-radius: 10px; font-size: calc(14.5px * var(--fs)); box-shadow: var(--shadow); transition: opacity .35s, transform .35s; }
.toast.warn { background: var(--c2); color: var(--on-accent); }
.toast.out { opacity: 0; transform: translateY(8px); }

/* ---------- 页脚 ---------- */
.foot { border-top: 1px solid var(--line); }
.foot-in { max-width: 1340px; margin: 0 auto; padding: 20px var(--gutter) 36px; display: flex; gap: 8px 24px; flex-wrap: wrap; justify-content: space-between; color: var(--ink-3); font-size: calc(13px * var(--fs)); }
:root[data-layout="wide"] :is(.topbar-in, .wrap, .foot-in, .chapter, .me, .lesson, .rv, .mk) { max-width: none; }
.foot-in p { margin: 0; max-width: 60em; }

/* ---------- 响应式 ---------- */
@media (max-width: 1180px) {
  .stage-cards { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .howto { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
@media (max-width: 1020px) {
  .hero { grid-template-columns: minmax(0, 1fr); }
  .auth { grid-template-columns: minmax(0, 1fr); grid-template-areas: "card" "pitch"; }
  .auth-card { position: static; max-width: 480px; width: 100%; margin: 0 auto; }
  .me-stats { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .stage-view { grid-template-columns: minmax(0, 1fr); gap: 18px; }
  .rail { position: static; max-height: none; overflow: visible; padding-right: 0; }
  .ch-list { display: none; }
  .ch-select-wrap { display: block; }
}
@media (max-width: 860px) {
  .topbar-in { padding: 8px 16px; gap: 8px 10px; }
  .tabs { order: 3; width: 100%; }
  .tab { flex: 1 1 0; align-items: center; padding: 4px 6px; }
  .top-tools { flex: 1 1 200px; }
  .brand-name small { display: none; }
  .home-more, .plan-grid { grid-template-columns: minmax(0, 1fr); }
}
@media (max-width: 640px) {
  .wrap { padding-inline: 16px; padding-block: 20px 56px; }
  .stage-cards, .howto { grid-template-columns: minmax(0, 1fr); }
  .yr { padding: 16px 0 10px 3px; }
  .yr-g { display: none; }
  .yr-n { font-size: calc(11px * var(--fs)); }
  .pt { padding: 20px 16px 22px; border-radius: 10px; }
  .pt-head { padding-right: 64px; }
  .stamp-btn { width: 62px; height: 62px; font-size: calc(11px * var(--fs)); right: -6px; top: -6px; }
  .pt.mastered .stamp-btn .st-on { font-size: calc(13px * var(--fs)); }
  .pt-key { padding: 10px 10px; }
  .step { padding-left: 38px; }
  .fc-face { padding: 20px 18px; }
  .pager { grid-template-columns: minmax(0, 1fr); }
  .pager .next { grid-column: 1; }
  .icon-btn .lbl, .login-btn .lbl { display: none; }
  .uname { display: none; }
  .user-chip { padding: 0 4px; }
  .auth-card { padding: 4px 18px 20px; }
  .me-forms { grid-template-columns: minmax(0, 1fr); }
  .me-stage { grid-template-columns: 44px minmax(0, 1fr) 54px; }
  .me-stage .btn { grid-column: 2 / 4; justify-self: start; }
  .me-chart { gap: 2px; }
  .ls-teacher { gap: 10px; }
  .ls-avatar { width: 40px; height: 40px; font-size: calc(22px * var(--fs)); }
  .ls-bubble { padding: 10px 14px 14px; }
  .ls-say { font-size: calc(16.5px * var(--fs)); }
  .ls-board { padding: 14px 12px; }
  .lq { padding: 12px; }
  .lq-q { font-size: calc(16px * var(--fs)); }
  .ls-nav .btn { min-height: 46px; padding: 0 14px; }
  .ls-count { display: none; }
  .rv-link { margin-left: 0; flex-basis: 100%; }
  .rv-tip { display: none; }
  .mk-pt { padding: 12px 14px 14px; }
  .mk-pt h3 small { margin-left: 0; flex-basis: 100%; }
}
/* 小屏手机：顶栏只留印章，把位置让给搜索框和按钮 */
@media (max-width: 480px) {
  .brand-name { display: none; }
}
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: .001ms !important; animation-iteration-count: 1 !important; transition-duration: .001ms !important; scroll-behavior: auto !important; }
  .fc-card { transition: none; }
}