/* ===== 主题变量：暗色（默认）===== */
:root {
  --bg: #0e0c17;
  --bg-2: #15121f;
  --bg-3: #1b1730;
  --surface: rgba(255, 255, 255, .04);
  --surface-2: rgba(255, 255, 255, .07);
  --border: rgba(255, 255, 255, .09);
  --border-strong: rgba(255, 255, 255, .16);

  --text: #f3efe7;
  --text-soft: #c8bfd4;
  --text-muted: #8a8299;

  --brand: #f59e0b;
  --brand-2: #f97316;
  --accent: #06b6d4;
  --grad: linear-gradient(120deg, #f59e0b 0%, #f97316 100%);
  --grad-soft: linear-gradient(120deg, rgba(245,158,11,.16), rgba(249,115,22,.16));

  --code-bg: #14111f;
  --code-out: #0d0b16;
  --shadow: 0 24px 60px -22px rgba(5, 4, 12, .8);
  --shadow-glow: 0 0 38px -10px rgba(249, 115, 22, .55);

  --topbar-h: 64px;
  --side-w: 286px;
  --content-w: 820px;
}

:root[data-theme="light"] {
  --bg: #faf6ec;
  --bg-2: #fffdf7;
  --bg-3: #f3ecdc;
  --surface: rgba(80, 55, 15, .045);
  --surface-2: rgba(80, 55, 15, .08);
  --border: rgba(80, 55, 15, .12);
  --border-strong: rgba(80, 55, 15, .22);

  --text: #2c2417;
  --text-soft: #5f5440;
  --text-muted: #9a8d72;

  --brand: #d97706;
  --brand-2: #ea580c;
  --accent: #0891b2;
  --grad: linear-gradient(120deg, #f59e0b 0%, #ea580c 100%);
  --grad-soft: linear-gradient(120deg, rgba(217,119,6,.12), rgba(234,88,12,.12));

  --code-bg: #1a1626;
  --code-out: #15121f;
  --shadow: 0 22px 50px -24px rgba(120, 80, 20, .35);
  --shadow-glow: 0 0 38px -12px rgba(234, 88, 12, .4);
}

/* ===== 基础重置 ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body {
  font-family: "PingFang SC", "Microsoft YaHei", "Hiragino Sans GB", "Segoe UI", system-ui, sans-serif;
  background: var(--bg); color: var(--text); line-height: 1.75;
  -webkit-font-smoothing: antialiased; transition: background .35s ease, color .35s ease;
}
a { color: inherit; text-decoration: none; }
ul { list-style: none; }
code, pre { font-family: ui-monospace, "SF Mono", Menlo, Consolas, monospace; }

/* ===== 背景装饰 ===== */
.bg-decor { position: fixed; inset: 0; z-index: -1; overflow: hidden; pointer-events: none; }
.blob { position: absolute; border-radius: 50%; filter: blur(110px); }
.blob-1 { width: 420px; height: 420px; background: #f59e0b; top: -160px; left: -100px; opacity: .25; }
.blob-2 { width: 380px; height: 380px; background: #f97316; top: 40%; right: -120px; opacity: .15; }
:root[data-theme="light"] .blob-1 { opacity: .14; }
:root[data-theme="light"] .blob-2 { opacity: .1; }

/* ===== 顶栏 ===== */
.topbar {
  position: fixed; top: 0; left: 0; right: 0; height: var(--topbar-h); z-index: 100;
  background: color-mix(in srgb, var(--bg) 82%, transparent);
  backdrop-filter: blur(18px); -webkit-backdrop-filter: blur(18px);
  border-bottom: 1px solid var(--border);
}
.topbar-inner { display: flex; align-items: center; gap: 16px; height: 100%; padding: 0 20px; }
.logo { display: flex; align-items: center; gap: 9px; font-weight: 800; font-size: 17px; white-space: nowrap; flex-shrink: 0; }
.logo-mark { font-size: 20px; }
.menu-toggle { display: none; background: none; border: none; color: var(--text); cursor: pointer; padding: 6px; border-radius: 8px; }
.menu-toggle:hover { background: var(--surface); }

.search {
  flex: 1; max-width: 360px; display: flex; align-items: center; gap: 8px;
  padding: 8px 14px; background: var(--surface); border: 1px solid var(--border); border-radius: 999px;
  color: var(--text-muted); transition: border-color .2s;
}
.search:focus-within { border-color: var(--brand); }
.search input { flex: 1; background: none; border: none; outline: none; color: var(--text); font-size: 14px; }
.search input::placeholder { color: var(--text-muted); }

.topbar-right { display: flex; align-items: center; gap: 8px; margin-left: auto; }
.icon-btn {
  display: inline-flex; align-items: center; gap: 6px; padding: 8px 12px; border-radius: 10px;
  background: var(--surface); border: 1px solid var(--border); color: var(--text-soft);
  cursor: pointer; font-size: 13px; font-weight: 600; transition: all .25s;
}
.icon-btn:hover { color: var(--brand); border-color: var(--border-strong); }
.run-badge { background: var(--grad); color: #fff; border: none; }
.run-badge:hover { filter: brightness(1.06); transform: translateY(-1px); }

.theme-toggle { padding: 8px; }
:root[data-theme="dark"] .icon-sun { display: none; }
:root[data-theme="light"] .icon-moon { display: none; }

/* ===== 布局 ===== */
.layout { display: flex; padding-top: var(--topbar-h); min-height: 100vh; }

/* ===== 侧边栏 ===== */
.sidebar {
  position: fixed; top: var(--topbar-h); left: 0; bottom: 0; width: var(--side-w);
  background: var(--bg-2); border-right: 1px solid var(--border);
  display: flex; flex-direction: column; z-index: 50; overflow: hidden;
}
.sidebar-head {
  display: flex; align-items: center; justify-content: space-between;
  width: calc(100% - 20px); margin: 14px 10px 6px; padding: 11px 14px;
  border-radius: 10px; background: var(--surface); border: 1px solid var(--border);
  color: var(--text); font-family: inherit; font-size: 13.5px; font-weight: 700;
  cursor: pointer; transition: all .2s;
}
.sidebar-head:hover { background: var(--surface-2); border-color: var(--border-strong); }
.sidebar-head.active { background: var(--grad-soft); color: var(--brand-2); border-color: var(--border-strong); }
.sidebar-head .rm-arrow { color: var(--text-muted); transition: transform .2s, color .2s; }
.sidebar-head:hover .rm-arrow, .sidebar-head.active .rm-arrow { transform: translateX(3px); color: var(--brand-2); }
.toc { flex: 1; overflow-y: auto; padding: 0 10px 16px; }
.toc-cat { margin-top: 14px; }
.toc-cat-title {
  font-size: 11px; font-weight: 700; letter-spacing: .8px; text-transform: uppercase;
  color: var(--text-muted); padding: 8px 12px 6px;
}
.toc-item {
  display: flex; align-items: center; gap: 10px; padding: 9px 12px; border-radius: 10px;
  color: var(--text-soft); font-size: 14px; cursor: pointer; transition: all .18s; position: relative;
}
.toc-item:hover { background: var(--surface); color: var(--text); }
.toc-item.active { background: var(--grad-soft); color: var(--brand-2); font-weight: 600; }
.toc-item.active::before {
  content: ""; position: absolute; left: 0; top: 50%; transform: translateY(-50%);
  width: 3px; height: 60%; background: var(--grad); border-radius: 2px;
}
.toc-icon { font-size: 16px; flex-shrink: 0; }
.toc-title { flex: 1; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.toc-check { font-size: 13px; opacity: 0; color: #34d399; flex-shrink: 0; }
.toc-item.done .toc-check { opacity: 1; }
.toc-item.hidden { display: none; }

.sidebar-foot { padding: 14px 16px; border-top: 1px solid var(--border); }
.progress-card { background: var(--surface); border: 1px solid var(--border); border-radius: 12px; padding: 12px 14px; }
.progress-label { font-size: 12px; color: var(--text-muted); margin-bottom: 8px; }
.progress-bar { height: 6px; background: var(--surface-2); border-radius: 999px; overflow: hidden; }
.progress-bar span { display: block; height: 100%; width: 0; background: var(--grad); border-radius: 999px; transition: width .5s cubic-bezier(.22,1,.36,1); }
.progress-text { font-size: 12px; color: var(--text-soft); margin-top: 8px; }

.overlay { display: none; position: fixed; inset: var(--topbar-h) 0 0 0; background: rgba(0,0,0,.5); z-index: 45; }

/* ===== 正文 ===== */
.content {
  flex: 1; margin-left: var(--side-w); padding: 40px 48px 80px; display: flex; justify-content: center;
}
.lesson { width: 100%; max-width: var(--content-w); }
.loading { color: var(--text-muted); text-align: center; padding: 60px; }

.lesson-head { margin-bottom: 30px; padding-bottom: 24px; border-bottom: 1px solid var(--border); }
.lesson-crumb { font-size: 13px; color: var(--text-muted); margin-bottom: 10px; display: block; }
.lesson-crumb .sep { margin: 0 6px; opacity: .6; }
.lesson-head h1 { font-size: clamp(1.7rem, 3.5vw, 2.3rem); font-weight: 800; letter-spacing: -.5px; line-height: 1.25; margin-bottom: 10px; }
.lesson-desc { font-size: 16px; color: var(--text-soft); }

.lesson-body { font-size: 16px; color: var(--text); }
.lesson-body h3 {
  font-size: 20px; font-weight: 700; margin: 34px 0 14px; padding-left: 12px;
  border-left: 3px solid var(--brand);
}
.lesson-body p { color: var(--text-soft); margin-bottom: 14px; }
.lesson-body p strong { color: var(--text); font-weight: 600; }
.lesson-body ul { margin: 0 0 16px; padding-left: 4px; }
.lesson-body ul li { position: relative; padding: 5px 0 5px 22px; color: var(--text-soft); }
.lesson-body ul li::before {
  content: ""; position: absolute; left: 4px; top: 13px; width: 6px; height: 6px;
  border-radius: 50%; background: var(--grad);
}
.lesson-body code.inline {
  padding: 2px 7px; border-radius: 5px; background: var(--surface-2); border: 1px solid var(--border);
  color: var(--brand-2); font-size: 13.5px;
}

/* 提示框 */
.b-callout {
  display: flex; gap: 12px; padding: 14px 16px; border-radius: 12px; margin: 18px 0;
  font-size: 14.5px; line-height: 1.7; border: 1px solid;
}
.b-callout .ico { font-size: 18px; flex-shrink: 0; line-height: 1.7; }
.b-callout .txt { color: var(--text-soft); }
.b-callout .txt strong { color: var(--text); }
.b-tip { background: rgba(6,182,212,.08); border-color: rgba(6,182,212,.25); }
.b-tip .ico { color: var(--accent); }
.b-warn { background: rgba(239,68,68,.08); border-color: rgba(239,68,68,.28); }
.b-warn .ico { color: #ef4444; }

/* ===== 代码块 ===== */
.codeblock {
  margin: 20px 0; background: var(--code-bg); border: 1px solid rgba(255,255,255,.1);
  border-radius: 14px; overflow: hidden; box-shadow: 0 10px 30px -16px rgba(0,0,0,.5);
}
.code-head {
  display: flex; align-items: center; gap: 10px; padding: 10px 14px;
  background: rgba(255,255,255,.04); border-bottom: 1px solid rgba(255,255,255,.07);
}
.code-lang { font-size: 12px; font-weight: 600; color: #c8bfd4; padding: 2px 9px; border-radius: 6px; background: rgba(255,255,255,.07); }
.code-spacer { flex: 1; }
.cb-btn {
  display: inline-flex; align-items: center; gap: 5px; padding: 5px 12px; border-radius: 8px;
  font-size: 12.5px; font-weight: 600; cursor: pointer; border: 1px solid rgba(255,255,255,.12);
  background: rgba(255,255,255,.05); color: #d8d0e6; transition: all .2s;
}
.cb-btn:hover { background: rgba(255,255,255,.12); }
.cb-btn.run { background: var(--grad); color: #fff; border: none; }
.cb-btn.run:hover { filter: brightness(1.08); }
.cb-btn.run.loading { opacity: .7; pointer-events: none; }
.cb-btn svg { width: 13px; height: 13px; }

.codeblock pre { margin: 0; padding: 18px 20px; overflow-x: auto; }
.codeblock code { font-size: 13.5px; line-height: 1.75; color: #e6e0f0; white-space: pre; }
/* Python 简易高亮 */
.tk-kw { color: #c084fc; }
.tk-str { color: #34d399; }
.tk-num { color: #fbbf24; }
.tk-cm { color: #6b7394; font-style: italic; }
.tk-fn { color: #60a5fa; }

.code-out {
  border-top: 1px solid rgba(255,255,255,.08); padding: 14px 20px; background: var(--code-out);
  font-size: 13px; line-height: 1.7; color: #b9f5cf; white-space: pre-wrap; word-break: break-word;
  max-height: 360px; overflow-y: auto;
}
.code-out.err { color: #fca5a5; }
.code-out .out-label { display: block; font-size: 11px; color: #8a8299; text-transform: uppercase; letter-spacing: 1px; margin-bottom: 6px; }
.code-out .out-running { color: #fbbf24; }
.code-spin { display: inline-block; width: 12px; height: 12px; border: 2px solid rgba(255,255,255,.25); border-top-color: var(--brand); border-radius: 50%; animation: spin .8s linear infinite; vertical-align: -2px; margin-right: 6px; }
@keyframes spin { to { transform: rotate(360deg); } }

/* ===== 学习路线图 ===== */
.roadmap .lesson-head { text-align: center; border-bottom: none; padding-bottom: 6px; }
.roadmap-body { display: flex; flex-direction: column; align-items: stretch; }
.rm-stage {
  background: var(--surface); border: 1px solid var(--border); border-left: 4px solid var(--stage-c);
  border-radius: 16px; padding: 22px 24px; transition: all .3s cubic-bezier(.22,1,.36,1);
}
.rm-stage:hover { border-color: var(--border-strong); transform: translateX(4px); }
.rm-stage-head { display: flex; align-items: center; gap: 16px; margin-bottom: 18px; }
.rm-stage-num {
  width: 42px; height: 42px; border-radius: 12px; background: var(--stage-c); color: #fff;
  display: grid; place-items: center; font-weight: 800; font-size: 18px; flex-shrink: 0;
  box-shadow: 0 8px 18px -8px var(--stage-c);
}
.rm-stage-info { flex: 1; }
.rm-stage-info h3 { font-size: 17px; margin: 0 0 2px; padding: 0; border: none; }
.rm-stage-info p { margin: 0; color: var(--text-muted); font-size: 13.5px; }
.rm-stage-progress {
  font-size: 12.5px; color: var(--text-soft); background: var(--surface-2);
  padding: 5px 12px; border-radius: 999px; flex-shrink: 0; border: 1px solid var(--border);
}
.rm-nodes { display: flex; flex-wrap: wrap; gap: 10px; }
.rm-node {
  display: flex; align-items: center; gap: 8px; padding: 8px 14px;
  background: var(--surface-2); border: 1px solid var(--border); border-radius: 999px;
  font-size: 13.5px; color: var(--text-soft); cursor: pointer; transition: all .2s;
}
.rm-node:hover { color: var(--text); border-color: var(--stage-c); background: var(--surface); transform: translateY(-2px); }
.rm-node.done { color: var(--text); border-color: rgba(52,211,153,.4); }
.rm-node-icon { font-size: 15px; }
.rm-node-check { color: #34d399; font-size: 13px; }
.rm-connector { display: flex; justify-content: center; padding: 6px 0; color: var(--text-muted); }
.rm-connector svg { opacity: .4; }
.rm-foot { text-align: center; margin-top: 34px; padding: 18px; color: var(--text-soft); font-size: 15px; background: var(--surface); border: 1px solid var(--border); border-radius: 14px; }

/* ===== 章节导航 ===== */
.lesson-nav { display: flex; justify-content: space-between; gap: 14px; margin-top: 50px; padding-top: 28px; border-top: 1px solid var(--border); }
.ln-link {
  flex: 1; display: flex; flex-direction: column; gap: 4px; padding: 16px 20px;
  background: var(--surface); border: 1px solid var(--border); border-radius: 14px; transition: all .25s;
}
.ln-link:hover { border-color: var(--border-strong); background: var(--surface-2); transform: translateY(-2px); }
.ln-link.next { text-align: right; }
.ln-link .ln-dir { font-size: 12px; color: var(--text-muted); }
.ln-link .ln-title { font-size: 15px; font-weight: 600; color: var(--text); }
.ln-link.disabled { opacity: .35; pointer-events: none; }

/* ===== Footer ===== */
.footer { margin-left: var(--side-w); border-top: 1px solid var(--border); background: var(--bg-2); padding: 50px 0 26px; }
.footer-inner { display: grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap: 32px; padding: 0 48px 32px; border-bottom: 1px solid var(--border); }
.footer-brand p { color: var(--text-muted); font-size: 13.5px; max-width: 300px; margin-top: 12px; line-height: 1.7; }
.footer-col h4 { font-size: 14px; margin-bottom: 12px; }
.footer-col a { display: block; color: var(--text-muted); font-size: 13.5px; padding: 4px 0; transition: color .2s; }
.footer-col a:hover { color: var(--brand-2); }
.footer-bottom { display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: 14px; padding: 22px 48px 0; }
.footer-bottom p { color: var(--text-muted); font-size: 13px; }
.beian-link {
  display: inline-flex; align-items: center; gap: 6px; color: var(--text-muted); font-size: 13px;
  padding: 6px 14px; border: 1px solid var(--border); border-radius: 8px; transition: all .25s;
}
.beian-link:hover { color: var(--brand-2); border-color: var(--border-strong); background: var(--surface); }

/* ===== Toast ===== */
.toast {
  position: fixed; bottom: 28px; left: 50%; transform: translateX(-50%) translateY(20px);
  background: var(--bg-3); color: var(--text); padding: 12px 22px; border-radius: 999px;
  border: 1px solid var(--border-strong); box-shadow: var(--shadow); font-size: 14px; z-index: 200;
  opacity: 0; transition: all .3s cubic-bezier(.22,1,.36,1); pointer-events: none;
}
.toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }

/* ===== 响应式 ===== */
@media (max-width: 900px) {
  :root { --side-w: 260px; }
  .content { padding: 30px 24px 60px; }
  .footer-inner { grid-template-columns: 1fr 1fr; padding: 0 28px 28px; }
}

@media (max-width: 768px) {
  .menu-toggle { display: inline-flex; }
  .search { max-width: none; }
  .run-badge span, .logo-text { display: none; }
  .sidebar {
    transform: translateX(-100%); transition: transform .32s cubic-bezier(.22,1,.36,1);
    box-shadow: var(--shadow);
  }
  .sidebar.open { transform: translateX(0); }
  .overlay.show { display: block; }
  .content, .footer { margin-left: 0; }
  .footer-inner { padding: 0 24px 24px; }
  .footer-bottom { padding: 22px 24px 0; flex-direction: column; text-align: center; }
  .lesson-nav { flex-direction: column; }
  .ln-link.next { text-align: left; }
}

@media (max-width: 480px) {
  .footer-inner { grid-template-columns: 1fr; }
  .content { padding: 24px 16px 50px; }
  .codeblock pre { padding: 14px; }
  .codeblock code { font-size: 12.5px; }
}

/* ===== 无障碍 ===== */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: .001ms !important; transition-duration: .001ms !important; scroll-behavior: auto !important; }
}