/* Python 从零开始。版式概念：一本写满荧光笔的练习本。正文安静，术语用 Python 黄标记，代码永远在深色的终端面板里。 */
:root {
  color-scheme: light;
  --page: #f5f7fb;
  --surface: #ffffff;
  --surface-2: #eef1f8;
  --ink-1: #16213a;
  --ink-2: #414c66;
  --ink-3: #667088;
  --line: #d9dfeb;
  --bar: #1b2a4a;
  --bar-ink: #f2f5fb;
  --bar-ink-2: #b4bfd6;
  --accent: #245a9c;
  --accent-ink: #ffffff;
  --accent-soft: #e4edf9;
  --marker: #ffd43b;
  --marker-soft: #ffe88a;
  --marker-ink: #16213a;
  --good: #0f7a3f;
  --good-soft: #e0f3e7;
  --bad: #b3302f;
  --bad-soft: #fbe8e7;
  --code-bg: #141b2d;
  --code-bg-2: #0f1524;
  --code-line: #2a3450;
  --code-text: #e7ebf5;
  --code-comment: #8a96b3;
  --code-keyword: #ffd43b;
  --code-string: #9fe0a8;
  --code-number: #ffb38a;
  --code-function: #8cc4ff;
  --code-active: rgba(255, 255, 255, 0.04);
  --code-select: rgba(140, 196, 255, 0.3);
  --code-error: rgba(255, 96, 96, 0.22);
  --code-err-text: #ff9d9d;
  --code-size: 14px;
  --font-ui: system-ui, -apple-system, "Segoe UI", "PingFang SC", "Microsoft YaHei", "Noto Sans CJK SC", sans-serif;
  --font-code: "Cascadia Code", "JetBrains Mono", "SF Mono", Menlo, Consolas, "Noto Sans Mono CJK SC", "Microsoft YaHei", monospace;
  --radius: 8px;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    color-scheme: dark;
    --page: #0f1422;
    --surface: #181f31;
    --surface-2: #20283d;
    --ink-1: #edf1f9;
    --ink-2: #c0c8db;
    --ink-3: #8e99b3;
    --line: #2f3950;
    --bar: #0c1120;
    --accent: #8cc4ff;
    --accent-ink: #0b1a2e;
    --accent-soft: #1d2d47;
    --marker-soft: #5a4a10;
    --marker-ink: #fff3c4;
    --good: #58cf8b;
    --good-soft: #15321f;
    --bad: #ff9d9d;
    --bad-soft: #3b2024;
    --code-bg: #0f1524;
    --code-bg-2: #0a0f1b;
  }
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --page: #0f1422;
  --surface: #181f31;
  --surface-2: #20283d;
  --ink-1: #edf1f9;
  --ink-2: #c0c8db;
  --ink-3: #8e99b3;
  --line: #2f3950;
  --bar: #0c1120;
  --accent: #8cc4ff;
  --accent-ink: #0b1a2e;
  --accent-soft: #1d2d47;
  --marker-soft: #5a4a10;
  --marker-ink: #fff3c4;
  --good: #58cf8b;
  --good-soft: #15321f;
  --bad: #ff9d9d;
  --bad-soft: #3b2024;
  --code-bg: #0f1524;
  --code-bg-2: #0a0f1b;
}

@media (pointer: coarse) {
  :root { --code-size: 16px; }
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-padding-top: 64px; }
body {
  margin: 0;
  background: var(--page);
  color: var(--ink-1);
  font: 16px/1.75 var(--font-ui);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}
[hidden] { display: none !important; }
a { color: var(--accent); }
h1, h2, h3 { line-height: 1.3; text-wrap: balance; margin: 0; }
p { margin: 0; }
button, input, textarea { font: inherit; color: inherit; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
main { flex: 1; outline: none; width: 100%; min-width: 0; }
.skip { position: absolute; left: -999px; top: 0; background: var(--surface); padding: 8px 12px; z-index: 50; }
.skip:focus { left: 8px; top: 8px; }
.muted { color: var(--ink-3); }
.small { font-size: 13px; }

/* 顶栏 */
.topbar {
  position: sticky;
  top: env(safe-area-inset-top, 0px);
  z-index: 20;
  display: flex;
  align-items: center;
  gap: 16px;
  background: var(--bar);
  color: var(--bar-ink);
  padding: 8px max(16px, env(safe-area-inset-right, 0px)) 8px max(16px, env(safe-area-inset-left, 0px));
}
.brand { display: inline-flex; align-items: center; gap: 8px; color: inherit; text-decoration: none; font-weight: 700; white-space: nowrap; }
.topnav { display: flex; gap: 2px; margin-left: auto; }
.topnav a { color: var(--bar-ink-2); text-decoration: none; padding: 4px 10px; border-radius: 6px; font-size: 14px; white-space: nowrap; }
.topnav a:hover { color: var(--bar-ink); }
.topnav a.current { color: var(--bar-ink); background: rgba(255, 255, 255, 0.12); }
.progress-chip { font-size: 12px; color: var(--bar-ink-2); white-space: nowrap; font-variant-numeric: tabular-nums; }

/* 按钮 */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  min-height: 36px;
  padding: 4px 14px;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: var(--surface);
  color: var(--ink-1);
  cursor: pointer;
  font-size: 14px;
  text-decoration: none;
  white-space: nowrap;
}
.btn:hover { background: var(--surface-2); }
.btn:disabled { opacity: 0.55; cursor: not-allowed; }
.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); font-weight: 600; }
.btn.primary:hover { filter: brightness(1.1); }
.btn.go { background: var(--marker); border-color: var(--marker); color: #16213a; font-weight: 700; }
.btn.go:hover { background: #ffdf66; }
.btn.stop { background: var(--bad); border-color: var(--bad); color: #fff; font-weight: 600; }
:root[data-theme="dark"] .btn.stop { color: #2a0f0f; }
.btn.quiet { background: transparent; }
.code-tools .btn:not(.go):not(.stop) { background: transparent; border-color: var(--code-line); color: var(--code-text); }
.code-tools .btn:not(.go):not(.stop):hover { background: rgba(255, 255, 255, 0.08); }

/* 首页 */
.hero {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1.05fr);
  gap: 40px;
  align-items: center;
  max-width: 1120px;
  margin: 0 auto;
  padding: 48px max(20px, env(safe-area-inset-right, 0px)) 40px max(20px, env(safe-area-inset-left, 0px));
}
.hero h1 { font-size: clamp(34px, 5vw, 52px); letter-spacing: -0.01em; }
.hero h1 mark { background: linear-gradient(transparent 80%, var(--marker) 80%, var(--marker) 94%, transparent 94%); color: inherit; padding: 0 2px; }
.hero-text { display: grid; gap: 18px; min-width: 0; }
.hero-lead { font-size: 18px; color: var(--ink-2); max-width: 30em; }
.hero-actions { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; }
.hero-facts { display: flex; flex-wrap: wrap; gap: 6px 18px; font-size: 14px; color: var(--ink-3); }
.hero-facts b { color: var(--ink-1); font-size: 16px; }
.big-btn { min-height: 46px; font-size: 16px; padding: 6px 22px; }

.course-map { max-width: 1120px; margin: 0 auto; padding: 8px max(20px, env(safe-area-inset-right, 0px)) 48px max(20px, env(safe-area-inset-left, 0px)); display: grid; gap: 14px; }
.map-title { font-size: 22px; margin-bottom: 4px; }
.map-module {
  display: grid;
  grid-template-columns: 240px minmax(0, 1fr);
  gap: 20px;
  padding: 18px 20px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}
.map-head h3 { font-size: 17px; }
.map-num { font-size: 12px; font-weight: 700; color: var(--ink-3); font-variant-numeric: tabular-nums; }
.map-en { font-size: 12px; color: var(--ink-3); font-family: var(--font-code); }
.map-intro { font-size: 14px; color: var(--ink-2); margin-top: 6px; line-height: 1.6; }
.map-bar { height: 4px; background: var(--surface-2); border-radius: 2px; overflow: hidden; margin-top: 10px; }
.map-bar i { display: block; height: 100%; background: var(--marker); }
.map-lessons { list-style: none; margin: 0; padding: 0; display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 2px 16px; align-content: start; }
.map-lessons a { display: flex; gap: 8px; align-items: baseline; padding: 3px 0; color: var(--ink-1); text-decoration: none; font-size: 15px; line-height: 1.5; }
.map-lessons a:hover { color: var(--accent); text-decoration: underline; }
.tick { flex: none; width: 16px; text-align: center; font-size: 13px; color: var(--ink-3); }
.tick.done { color: var(--good); font-weight: 700; }

/* 课程页 */
.lesson-shell {
  display: grid;
  grid-template-columns: 260px minmax(0, 1fr);
  gap: 36px;
  max-width: 1120px;
  margin: 0 auto;
  padding: 24px max(20px, env(safe-area-inset-right, 0px)) 48px max(20px, env(safe-area-inset-left, 0px));
  align-items: start;
}
.side { position: sticky; top: 64px; max-height: calc(100vh - 80px); overflow-y: auto; font-size: 14px; padding-right: 4px; }
.side h2 { font-size: 13px; color: var(--ink-3); font-weight: 700; margin-bottom: 6px; }
.side ul { list-style: none; margin: 0; padding: 0; }
.side a { display: flex; gap: 6px; align-items: baseline; padding: 5px 8px; border-radius: 5px; color: var(--ink-2); text-decoration: none; line-height: 1.45; }
.side a:hover { background: var(--surface-2); }
.side a.current { background: var(--accent-soft); color: var(--ink-1); font-weight: 600; }
.side .all { display: block; margin-top: 10px; font-size: 13px; padding: 5px 8px; color: var(--accent); }
.article { min-width: 0; display: grid; grid-template-columns: minmax(0, 1fr); gap: 20px; max-width: 760px; }
.crumb { font-size: 13px; color: var(--ink-3); }
.crumb a { color: inherit; }
.lesson-title { font-size: clamp(26px, 4vw, 34px); }
.lesson-en { font-family: var(--font-code); font-size: 14px; color: var(--ink-3); margin-top: 4px; }

/* 正文 */
.prose { min-width: 0; }
.prose > * + * { margin-top: 14px; }
.prose h2 { font-size: 21px; margin-top: 28px; }
.prose h2:first-child { margin-top: 0; }
.prose ul, .prose ol { padding-left: 22px; margin-bottom: 0; }
.prose li + li { margin-top: 5px; }
.prose code { font-family: var(--font-code); font-size: 0.88em; background: var(--surface-2); padding: 1px 5px; border-radius: 4px; white-space: break-spaces; }
.prose pre { background: var(--code-bg); color: var(--code-text); padding: 12px 14px; border-radius: 6px; overflow-x: auto; line-height: 1.6; font-size: var(--code-size); margin-bottom: 0; }
.prose pre code { background: none; padding: 0; font-size: inherit; color: inherit; white-space: pre; }
.prose table { display: block; overflow-x: auto; border-collapse: collapse; font-size: 14.5px; max-width: 100%; }
.prose th, .prose td { border: 1px solid var(--line); padding: 6px 12px; text-align: left; white-space: nowrap; }
.prose td { white-space: normal; min-width: 54px; }
.prose th { background: var(--surface-2); font-weight: 600; }
.term { background: linear-gradient(transparent 60%, var(--marker-soft) 60%); font-weight: 600; padding: 0 1px; }
.term-en { font-family: var(--font-code); font-weight: 400; font-size: 0.74em; color: var(--ink-2); margin-left: 4px; }

/* 代码面板 */
.code-card { background: var(--code-bg); border-radius: var(--radius); overflow: hidden; min-width: 0; box-shadow: 0 0 0 1px var(--code-line); }
.code-editor { min-width: 0; max-height: 460px; overflow: auto; }
.code-tools { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; padding: 8px 10px; background: var(--code-bg-2); border-top: 1px solid var(--code-line); }
.code-tools .spacer { flex: 1; }
.code-tools .hint-key { font-size: 12px; color: var(--code-comment); }
.key-row { display: none; gap: 4px; padding: 6px 8px; background: var(--code-bg-2); border-top: 1px solid var(--code-line); overflow-x: auto; }
.key-row button { flex: none; min-width: 38px; height: 34px; border: 1px solid var(--code-line); background: transparent; color: var(--code-text); border-radius: 5px; font-family: var(--font-code); font-size: 15px; }
@media (pointer: coarse) { .key-row { display: flex; } .hint-key { display: none; } }
.console { background: var(--code-bg-2); border-top: 1px solid var(--code-line); color: var(--code-text); font-family: var(--font-code); font-size: var(--code-size); line-height: 1.6; padding: 10px 14px; }
.console-out { margin: 0; white-space: pre-wrap; word-break: break-word; font: inherit; max-height: 320px; overflow-y: auto; }
.console-out .err { color: var(--code-err-text); }
.console-out .echo { color: var(--code-keyword); }
.console-status { color: var(--code-comment); font-size: 13px; font-family: var(--font-ui); }
.console-input { display: flex; gap: 8px; align-items: center; margin-top: 6px; }
.console-input span { color: var(--code-keyword); }
.console-input input {
  flex: 1;
  min-width: 0;
  height: 36px;
  padding: 0 10px;
  background: var(--code-bg);
  color: var(--code-text);
  border: 1px solid var(--code-keyword);
  border-radius: 5px;
  font: inherit;
}
.preset { padding: 8px 12px; background: var(--code-bg-2); border-top: 1px solid var(--code-line); color: var(--code-comment); font-size: 13px; }
.preset textarea { width: 100%; margin-top: 4px; background: var(--code-bg); color: var(--code-text); border: 1px solid var(--code-line); border-radius: 5px; font-family: var(--font-code); padding: 6px 8px; }

/* 报错卡 */
.error-card { margin-top: 8px; padding: 10px 12px; border-radius: 6px; background: rgba(255, 96, 96, 0.12); box-shadow: inset 0 0 0 1px rgba(255, 130, 130, 0.45); font-family: var(--font-ui); font-size: 14px; color: var(--code-text); line-height: 1.6; }
.error-card .where { font-weight: 700; }
.error-card code { font-family: var(--font-code); display: block; margin: 4px 0; color: var(--code-err-text); white-space: pre-wrap; word-break: break-word; }
.error-card .raw { font-family: var(--font-code); font-size: 13px; color: var(--code-err-text); word-break: break-word; }
.error-card .fix { margin-top: 6px; }
.error-card .fix b { color: var(--code-keyword); }

/* 选择题 */
.quiz { padding: 16px 18px; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); display: grid; gap: 10px; min-width: 0; }
.block-tag { font-size: 12px; font-weight: 700; color: var(--ink-3); }
.quiz pre { margin: 0; background: var(--code-bg); color: var(--code-text); padding: 10px 14px; border-radius: 6px; overflow-x: auto; font-family: var(--font-code); font-size: var(--code-size); line-height: 1.6; }
.quiz-question > * { margin: 0; }
.quiz-question p + p { margin-top: 8px; }
.quiz-question code { font-family: var(--font-code); font-size: 0.88em; background: var(--surface-2); padding: 1px 5px; border-radius: 4px; }
.quiz-options { display: grid; gap: 6px; }
.quiz-option {
  display: block;
  width: 100%;
  text-align: left;
  padding: 8px 12px;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: var(--surface);
  cursor: pointer;
  line-height: 1.5;
  white-space: pre-wrap;
}
.quiz-option.mono { font-family: var(--font-code); font-size: 14.5px; }
.quiz-option:hover:not(:disabled) { background: var(--surface-2); }
.quiz-option:disabled { cursor: default; }
.quiz-option.right { background: var(--good-soft); border-color: var(--good); color: var(--ink-1); font-weight: 600; }
.quiz-option.wrong { background: var(--bad-soft); border-color: var(--bad); }
.feedback { font-size: 15px; }
.feedback p { margin: 0; }
.feedback code { font-family: var(--font-code); font-size: 0.88em; background: var(--surface-2); padding: 1px 5px; border-radius: 4px; }
.feedback .verdict { font-weight: 700; }
.feedback .verdict.good { color: var(--good); }
.feedback .verdict.bad { color: var(--bad); }

/* 练习 */
.exercise { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); min-width: 0; overflow: hidden; }
.exercise.passed { border-color: var(--good); }
.ex-head { padding: 14px 18px 12px; display: grid; gap: 6px; }
.ex-title { display: flex; flex-wrap: wrap; gap: 4px 10px; align-items: baseline; }
.ex-title h3 { font-size: 17px; }
.ex-state { font-size: 12px; font-weight: 700; color: var(--good); }
.ex-prompt > * { margin: 0; }
.ex-prompt > * + * { margin-top: 8px; }
.ex-prompt code { font-family: var(--font-code); font-size: 0.88em; background: var(--surface-2); padding: 1px 5px; border-radius: 4px; }
.ex-prompt pre { background: var(--surface-2); padding: 8px 12px; border-radius: 6px; overflow-x: auto; }
.ex-prompt pre code { background: none; padding: 0; }
.ex-prompt ul { padding-left: 20px; }
.exercise .code-card { border-radius: 0; box-shadow: none; }
.ex-result { padding: 12px 18px; display: grid; gap: 10px; border-top: 1px solid var(--line); font-size: 14.5px; min-width: 0; }
.ex-verdict { font-weight: 700; }
.ex-verdict.good { color: var(--good); }
.ex-verdict.bad { color: var(--bad); }
.case { display: grid; gap: 4px; padding: 8px 10px; background: var(--surface-2); border-radius: 6px; min-width: 0; }
.case-head { font-size: 13px; color: var(--ink-2); }
.case-compare { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 8px; }
.case-compare > div { min-width: 0; }
.case-compare span { font-size: 12px; color: var(--ink-3); }
.case-compare pre { margin: 2px 0 0; padding: 6px 8px; background: var(--surface); border-radius: 4px; font-family: var(--font-code); font-size: 13.5px; white-space: pre-wrap; word-break: break-word; max-height: 180px; overflow-y: auto; }
.case-hint { font-size: 14px; color: var(--ink-1); font-weight: 600; }
.ex-extra { padding: 10px 18px 14px; border-top: 1px solid var(--line); display: grid; gap: 8px; font-size: 14.5px; }
.ex-actions { display: flex; flex-wrap: wrap; gap: 8px; }
.hint-box { padding: 8px 12px; background: var(--accent-soft); border-radius: 6px; }
.hint-box > * { margin: 0; }
.hint-box code { font-family: var(--font-code); font-size: 0.88em; background: var(--surface); padding: 1px 5px; border-radius: 4px; }
.solution-box { display: grid; gap: 6px; }
.solution-box pre { margin: 0; background: var(--code-bg); color: var(--code-text); padding: 10px 14px; border-radius: 6px; overflow-x: auto; font-family: var(--font-code); font-size: var(--code-size); line-height: 1.6; }

/* 课程结尾 */
.lesson-end { display: grid; gap: 12px; padding: 16px 18px; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); }
.lesson-end.complete { background: var(--good-soft); border-color: var(--good); }
.pager { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 10px; }

/* 其他页 */
.page { max-width: 820px; margin: 0 auto; padding: 28px max(20px, env(safe-area-inset-right, 0px)) 48px max(20px, env(safe-area-inset-left, 0px)); display: grid; grid-template-columns: minmax(0, 1fr); gap: 16px; }
.page h1 { font-size: 28px; }
.panel { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 16px 18px; display: grid; gap: 10px; min-width: 0; }
.panel h2 { font-size: 17px; }
.search-input { height: 40px; padding: 0 12px; border: 1px solid var(--line); border-radius: 6px; background: var(--surface); width: 100%; }
.table-wrap { overflow-x: auto; }
table.gloss { width: 100%; border-collapse: collapse; font-size: 15px; }
table.gloss th, table.gloss td { padding: 8px 10px; border-bottom: 1px solid var(--line); text-align: left; }
table.gloss th { font-size: 13px; color: var(--ink-3); font-weight: 600; }
table.gloss td:first-child { font-family: var(--font-code); font-size: 14px; }
.stat-row { display: flex; flex-wrap: wrap; gap: 8px 32px; }
.stat-label { font-size: 13px; color: var(--ink-3); }
.stat-value { font-size: 26px; font-weight: 700; line-height: 1.25; }
.row { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; }
.sr { position: absolute; width: 1px; height: 1px; overflow: hidden; clip-path: inset(50%); white-space: nowrap; }
.state { padding: 40px 20px; text-align: center; color: var(--ink-2); display: grid; gap: 12px; justify-items: center; }

.foot { padding: 14px max(20px, env(safe-area-inset-right, 0px)) calc(14px + env(safe-area-inset-bottom, 0px)) max(20px, env(safe-area-inset-left, 0px)); font-size: 13px; color: var(--ink-3); text-align: center; border-top: 1px solid var(--line); }
.foot a { color: inherit; }
.noscript { padding: 20px; }

@media (max-width: 900px) {
  .hero { grid-template-columns: minmax(0, 1fr); gap: 24px; padding-top: 28px; }
  .lesson-shell { grid-template-columns: minmax(0, 1fr); padding-top: 16px; }
  .side { display: none; }
  .article { max-width: none; }
  .map-module { grid-template-columns: minmax(0, 1fr); gap: 12px; }
}
@media (max-width: 560px) {
  .brand span { display: none; }
  .topbar { gap: 8px; }
  .topnav { margin-left: auto; }
  .progress-chip { display: none; }
  .case-compare { grid-template-columns: minmax(0, 1fr); }
}
@media (prefers-reduced-motion: reduce) {
  * { scroll-behavior: auto !important; transition: none !important; animation: none !important; }
}