/* ============================================================================
   AI 时代 · 如何学习与开发 —— 课件设计系统
   暖米白 + 珊瑚 + 细线条，编辑级 tech 美学。中文排版遵循 djhh 规则。
   ========================================================================== */

:root {
  /* 纸感暖底 */
  --paper:      #F7F1E6;
  --paper-2:    #FBF7EF;
  --paper-card: #FFFDF8;
  --paper-sink: #EFE7D6;
  /* 墨色 */
  --ink:        #2A2620;
  --ink-2:      #4A4238;
  --ink-3:      #7A7060;
  --ink-faint:  #A89A82;
  /* 珊瑚主强调 */
  --coral:      #E5643C;
  --coral-deep: #C84E2A;
  --coral-soft: #F4A26133;
  --coral-glow: #E5643C22;
  /* 辅助（克制使用） */
  --sage:       #7C8B6B;
  --dusty:      #6B84A0;
  --clay:       #B08150;
  --gold:       #D9A441;
  /* 线 */
  --line:       #E3D8C4;
  --line-2:     #D6C8AE;
  --line-ink:   #2A262033;
  /* 阴影 */
  --shadow-sm:  0 1px 2px #2a26200f, 0 2px 8px #2a262010;
  --shadow-md:  0 4px 14px #2a262014, 0 10px 40px #2a26201a;
  --shadow-lg:  0 10px 30px #2a262018, 0 30px 80px #6b4a2a1f;
  /* 尺度 */
  --maxw: 1120px;
  --prose: 42ch;
  --radius: 16px;
  --radius-sm: 10px;
  /* 字体 */
  --sans: "PingFang SC", "Noto Sans SC", "Hiragino Sans GB", "Microsoft YaHei", -apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, sans-serif;
  --serif: "Songti SC", "Noto Serif SC", Georgia, "Times New Roman", serif;
  --mono: "SF Mono", "JetBrains Mono", "Fira Code", ui-monospace, "Cascadia Code", Menlo, monospace;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background:
    radial-gradient(1200px 600px at 78% -8%, #fdf6e8 0%, transparent 60%),
    radial-gradient(900px 500px at -5% 12%, #f7ecda 0%, transparent 55%),
    var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 17px;
  line-height: 1.75;
  font-feature-settings: "kern" 1, "liga" 1;
  hanging-punctuation: allow-end;
  overflow-x: hidden;
}

/* ---- djhh: 中文排版默认规则 ---- */
h1, h2, h3, h4, h5, .balance, dt, figcaption, .card-title, .kicker {
  word-break: keep-all;
  text-wrap: balance;
}
p, li, dd, .prose, td, th, .lede {
  word-break: keep-all;
  text-wrap: pretty;
}
.num, .stat-num, .price, time, .nowrap {
  white-space: nowrap;
  font-variant-numeric: tabular-nums;
}

/* ---- 排版基元 ---- */
.wrap { max-width: var(--maxw); margin-inline: auto; padding-inline: clamp(20px, 5vw, 48px); }
.prose { max-width: var(--prose); }
.prose-wide { max-width: 58ch; }

h1, h2, h3, h4 { line-height: 1.2; margin: 0 0 .5em; font-weight: 700; letter-spacing: -0.01em; }
h1 { font-size: clamp(2rem, 5vw, 3.4rem); }
h2 { font-size: clamp(1.6rem, 3.4vw, 2.5rem); }
h3 { font-size: clamp(1.2rem, 2.2vw, 1.55rem); }
.display { font-family: var(--serif); font-weight: 600; letter-spacing: -0.02em; }

.kicker {
  display: inline-flex; align-items: center; gap: .55em;
  font-size: .8rem; font-weight: 700; letter-spacing: .12em;
  text-transform: uppercase; color: var(--coral-deep);
}
.kicker::before { content: ""; width: 1.8em; height: 2px; background: var(--coral); border-radius: 2px; }

.lede { font-size: clamp(1.05rem, 1.8vw, 1.3rem); color: var(--ink-2); max-width: 52ch; }
.muted { color: var(--ink-3); }
.faint { color: var(--ink-faint); }
strong, b { font-weight: 700; color: var(--ink); }
mark { background: linear-gradient(180deg, transparent 55%, var(--coral-soft) 55%); color: inherit; padding: 0 .1em; }
em.term { font-style: normal; color: var(--coral-deep); font-weight: 600; }
code {
  font-family: var(--mono); font-size: .88em;
  background: var(--paper-sink); color: var(--coral-deep);
  padding: .12em .42em; border-radius: 6px; border: 1px solid var(--line);
  white-space: nowrap;
}
a { color: var(--coral-deep); text-decoration-color: var(--coral-soft); text-underline-offset: 3px; }

/* ============================================================================
   顶部进度 + 导航
   ========================================================================== */
#progress {
  position: fixed; top: 0; left: 0; height: 3px; width: 0%;
  background: linear-gradient(90deg, var(--coral), var(--gold));
  z-index: 100; transition: width .1s linear;
  box-shadow: 0 0 12px var(--coral-glow);
}
#topnav {
  position: fixed; top: 0; left: 0; right: 0; z-index: 90;
  display: flex; align-items: center; justify-content: space-between;
  padding: 12px clamp(16px, 4vw, 40px);
  background: color-mix(in srgb, var(--paper) 78%, transparent);
  backdrop-filter: blur(14px) saturate(1.2);
  border-bottom: 1px solid transparent;
  transition: border-color .3s, background .3s;
}
#topnav.scrolled { border-bottom-color: var(--line); }
#topnav .brand { font-weight: 800; letter-spacing: -.01em; font-size: .98rem; display: flex; align-items: center; gap: .5em; }
#topnav .brand .dot { width: 10px; height: 10px; border-radius: 50%; background: var(--coral); box-shadow: 0 0 0 4px var(--coral-glow); }
#topnav .nav-links { display: flex; gap: 4px; }
#topnav .nav-links a {
  font-size: .82rem; color: var(--ink-3); text-decoration: none;
  padding: 6px 11px; border-radius: 99px; transition: .18s; white-space: nowrap;
}
#topnav .nav-links a:hover { color: var(--ink); background: var(--paper-sink); }
#topnav .nav-links a.active { color: var(--coral-deep); background: var(--coral-soft); font-weight: 600; }
@media (max-width: 820px) { #topnav .nav-links { display: none; } }

/* ============================================================================
   区块骨架
   ========================================================================== */
.section { padding: clamp(64px, 10vh, 120px) 0; position: relative; }
.section + .section { border-top: 1px solid var(--line); }
.section-head { margin-bottom: clamp(32px, 5vw, 56px); }
.section-head .idx {
  font-family: var(--serif); font-size: 1rem; color: var(--coral);
  font-weight: 700; letter-spacing: .05em;
}
.section-head h2 { margin-top: .2em; }

/* 幕分隔 */
.act-divider { padding: clamp(56px, 9vh, 104px) 0; text-align: center; position: relative; overflow: hidden; }
.act-divider .act-img { width: min(340px, 66vw); margin: 0 auto clamp(20px, 3vw, 30px); border-radius: 22px; overflow: hidden; border: 1px solid var(--line); box-shadow: var(--shadow-lg); position: relative; }
.act-divider .act-img img { width: 100%; height: auto; display: block; }
.act-divider .act-img .act-no-badge { position: absolute; top: 14px; left: 16px; font-family: var(--serif); font-size: 2.2rem; font-weight: 700; color: #fff; line-height: 1; text-shadow: 0 2px 12px #2a262066; }
.act-divider .act-no { font-family: var(--serif); font-size: clamp(3rem, 12vw, 7rem); color: var(--line-2); line-height: 1; font-weight: 600; }
.act-divider h2 { margin: .1em 0 .3em; }
.act-divider .act-sub { color: var(--ink-3); max-width: 40ch; margin-inline: auto; }

/* ============================================================================
   卡片 / 网格
   ========================================================================== */
.grid { display: grid; gap: clamp(16px, 2.2vw, 26px); }
.g2 { grid-template-columns: repeat(2, 1fr); }
.g3 { grid-template-columns: repeat(3, 1fr); }
.g4 { grid-template-columns: repeat(4, 1fr); }
@media (max-width: 900px) { .g3, .g4 { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 620px) { .g2, .g3, .g4 { grid-template-columns: 1fr; } }

.card {
  background: var(--paper-card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: clamp(20px, 2.4vw, 28px);
  box-shadow: var(--shadow-sm);
  transition: transform .25s cubic-bezier(.2,.7,.2,1), box-shadow .25s, border-color .25s;
}
.card:hover { transform: translateY(-3px); box-shadow: var(--shadow-md); border-color: var(--line-2); }
.card .card-title { font-weight: 700; font-size: 1.08rem; margin-bottom: .3em; display: flex; align-items: center; gap: .5em; }
.card .card-ico { font-size: 1.3em; }
.card p { margin: .4em 0 0; color: var(--ink-2); font-size: .96rem; }
.card.accent { border-color: var(--coral); background: linear-gradient(180deg, #fff8ef, var(--paper-card)); }
.card.dark { background: linear-gradient(160deg, #2c2822, #211d18); color: #f0e8d8; border-color: #3a352c; }
.card.dark .card-title, .card.dark p, .card.dark strong { color: #f4ecdd; }
.card.dark .muted { color: #b8ab93; }

/* 概念图 + 图注 */
figure { margin: 0; }
.figuromo { border-radius: var(--radius); overflow: hidden; border: 1px solid var(--line); background: var(--paper-2); box-shadow: var(--shadow-md); }
.figuromo img { display: block; width: 100%; height: auto; }
figcaption { font-size: .85rem; color: var(--ink-3); margin-top: .7em; padding-left: .9em; border-left: 2px solid var(--coral); }

.media-split { display: grid; grid-template-columns: 1fr 1fr; gap: clamp(28px, 5vw, 64px); align-items: center; }
.media-split.rev > :first-child { order: 2; }
@media (max-width: 860px) { .media-split { grid-template-columns: 1fr; } .media-split.rev > :first-child { order: 0; } }

/* 统计数字 */
.stat { text-align: left; }
.stat-num { font-family: var(--serif); font-size: clamp(2rem, 4vw, 3rem); font-weight: 700; color: var(--coral-deep); line-height: 1; letter-spacing: -.02em; }
.stat-label { color: var(--ink-3); font-size: .9rem; margin-top: .4em; }

/* 标签/药丸 */
.pill { display: inline-flex; align-items: center; gap: .4em; font-size: .78rem; font-weight: 600; padding: .3em .8em; border-radius: 99px; background: var(--paper-sink); color: var(--ink-2); border: 1px solid var(--line); white-space: nowrap; }
.pill.coral { background: var(--coral-soft); color: var(--coral-deep); border-color: transparent; }
.pill.sage  { background: #7c8b6b22; color: #55603f; }
.pill.dusty { background: #6b84a022; color: #405266; }

/* 要点列表 */
.checks { list-style: none; padding: 0; margin: 0; display: grid; gap: .7em; }
.checks li { position: relative; padding-left: 1.9em; color: var(--ink-2); }
.checks li::before { content: ""; position: absolute; left: 0; top: .5em; width: 1.1em; height: 1.1em; border-radius: 50%; background: var(--coral-soft); }
.checks li::after { content: ""; position: absolute; left: .34em; top: .74em; width: .42em; height: .24em; border-left: 2px solid var(--coral-deep); border-bottom: 2px solid var(--coral-deep); transform: rotate(-45deg); }

/* 引述 */
blockquote { margin: 1.4em 0; padding: 1em 1.4em; border-left: 3px solid var(--coral); background: linear-gradient(90deg, var(--coral-glow), transparent); border-radius: 0 var(--radius-sm) var(--radius-sm) 0; font-size: 1.08rem; color: var(--ink); }
blockquote .src { display: block; margin-top: .5em; font-size: .82rem; color: var(--ink-3); }

/* 表格 */
.table-wrap { overflow-x: auto; border: 1px solid var(--line); border-radius: var(--radius); background: var(--paper-card); box-shadow: var(--shadow-sm); }
table.data { width: 100%; border-collapse: collapse; font-size: .92rem; min-width: 560px; }
table.data th, table.data td { padding: .8em 1em; text-align: left; border-bottom: 1px solid var(--line); vertical-align: top; }
table.data thead th { background: var(--paper-sink); font-weight: 700; font-size: .82rem; letter-spacing: .03em; color: var(--ink-2); position: sticky; top: 0; }
table.data tbody tr:hover { background: #fff8ee; }
table.data tbody tr:last-child td { border-bottom: none; }
table.data .num { color: var(--coral-deep); font-weight: 600; }

/* 提示框 */
.callout { display: flex; gap: 1em; padding: 1.1em 1.3em; border-radius: var(--radius); border: 1px solid var(--line); background: var(--paper-2); }
.callout .ci { font-size: 1.5em; line-height: 1; }
.callout.warn { border-color: #d9a44155; background: #fbf3df; }
.callout.key  { border-color: var(--coral); background: linear-gradient(180deg,#fff6ec,#fffdf8); }
.callout .ctxt { flex: 1; }
.callout .ctxt strong { display: block; margin-bottom: .2em; }
.callout p { margin: 0; font-size: .95rem; }

/* ============================================================================
   交互组件通用外壳
   ========================================================================== */
.lab {
  border: 1px solid var(--line-2); border-radius: var(--radius);
  background:
    linear-gradient(180deg, #fffdf9, #fbf6ec);
  box-shadow: var(--shadow-md); overflow: hidden;
  position: relative;
}
.lab-head { display: flex; align-items: center; justify-content: space-between; gap: 1em; padding: 14px 18px; border-bottom: 1px solid var(--line); background: #fff9f0; }
.lab-head .lab-title { font-weight: 700; font-size: .95rem; display: flex; align-items: center; gap: .5em; }
.lab-head .lab-title .tag { font-size: .68rem; font-weight: 700; letter-spacing: .1em; color: var(--coral-deep); background: var(--coral-soft); padding: .25em .7em; border-radius: 99px; text-transform: uppercase; }
.lab-body { padding: clamp(18px, 3vw, 30px); }
.lab-hint { font-size: .82rem; color: var(--ink-3); }

/* 通用按钮/控件 */
.btn { font-family: inherit; font-size: .9rem; font-weight: 600; cursor: pointer; border: 1px solid var(--line-2); background: var(--paper-card); color: var(--ink); padding: .55em 1.1em; border-radius: 99px; transition: .18s; }
.btn:hover { border-color: var(--coral); color: var(--coral-deep); transform: translateY(-1px); }
.btn.primary { background: var(--coral); color: #fff; border-color: var(--coral); box-shadow: 0 4px 14px var(--coral-glow); }
.btn.primary:hover { background: var(--coral-deep); color: #fff; }
.btn.active { background: var(--ink); color: var(--paper); border-color: var(--ink); }
.seg { display: inline-flex; background: var(--paper-sink); border-radius: 99px; padding: 3px; gap: 2px; }
.seg button { border: none; background: transparent; font: inherit; font-size: .84rem; font-weight: 600; color: var(--ink-3); padding: .4em .95em; border-radius: 99px; cursor: pointer; transition: .16s; }
.seg button.on { background: var(--paper-card); color: var(--coral-deep); box-shadow: var(--shadow-sm); }

input[type="range"] { -webkit-appearance: none; appearance: none; width: 100%; height: 6px; border-radius: 99px; background: var(--paper-sink); outline: none; }
input[type="range"]::-webkit-slider-thumb { -webkit-appearance: none; width: 20px; height: 20px; border-radius: 50%; background: var(--coral); cursor: pointer; border: 3px solid #fff; box-shadow: var(--shadow-sm); }
.toggle { display: inline-flex; align-items: center; gap: .6em; cursor: pointer; user-select: none; font-size: .9rem; }
.toggle .tk { width: 40px; height: 23px; border-radius: 99px; background: var(--paper-sink); position: relative; transition: .2s; border: 1px solid var(--line-2); }
.toggle .tk::after { content: ""; position: absolute; top: 2px; left: 2px; width: 17px; height: 17px; border-radius: 50%; background: #fff; box-shadow: var(--shadow-sm); transition: .2s; }
.toggle input { display: none; }
.toggle input:checked + .tk { background: var(--coral); border-color: var(--coral); }
.toggle input:checked + .tk::after { transform: translateX(17px); }

/* 进度条通用 */
.meter { height: 12px; border-radius: 99px; background: var(--paper-sink); overflow: hidden; position: relative; }
.meter > span { display: block; height: 100%; border-radius: 99px; background: linear-gradient(90deg, var(--coral), var(--gold)); transition: width .5s cubic-bezier(.2,.7,.2,1); }

/* ============================================================================
   滚动揭示动画
   ========================================================================== */
.reveal { opacity: 0; transform: translateY(22px); transition: opacity .7s ease, transform .7s cubic-bezier(.2,.7,.2,1); }
.reveal.in { opacity: 1; transform: none; }
.reveal.d1 { transition-delay: .08s; } .reveal.d2 { transition-delay: .16s; }
.reveal.d3 { transition-delay: .24s; } .reveal.d4 { transition-delay: .32s; }
@media (prefers-reduced-motion: reduce) { .reveal { opacity: 1; transform: none; transition: none; } html { scroll-behavior: auto; } }

/* ============================================================================
   页脚
   ========================================================================== */
footer { padding: 64px 0 80px; border-top: 1px solid var(--line); color: var(--ink-3); font-size: .9rem; text-align: center; }
footer .sources { max-width: 720px; margin: 1.5em auto 0; text-align: left; font-size: .8rem; columns: 2; column-gap: 2em; }
@media (max-width: 640px){ footer .sources { columns: 1; } }
footer .sources a { display: block; margin-bottom: .35em; color: var(--ink-3); text-decoration: none; }
footer .sources a:hover { color: var(--coral-deep); }

/* ============================================================================
   左右翻页 · 横向卡片流（deck）
   把竖向长页改成一页页横向翻；内容多的页在页内纵向滚动，交互全保留。
   ========================================================================== */
html, body { height: 100%; }
body { overflow: hidden; }

#deck { position: fixed; inset: 0; z-index: 1; }
#track {
  display: flex; flex-flow: row nowrap; height: 100%;
  overflow-x: auto; overflow-y: hidden;
  scroll-behavior: smooth;
  overscroll-behavior: contain; overflow-anchor: none;
  scrollbar-width: none; -ms-overflow-style: none;
}
#track::-webkit-scrollbar { width: 0; height: 0; display: none; }

/* 每一页 = 满屏一屏；超屏内容页内纵向滚动 */
#track > * {
  flex: 0 0 100%; width: 100%; height: 100%; min-height: 0;
  overflow-y: auto; overflow-x: hidden;
  display: flex; flex-direction: column;
  scrollbar-width: thin; scrollbar-color: var(--line-2) transparent;
  -webkit-overflow-scrolling: touch;
}
#track > *::-webkit-scrollbar { width: 8px; }
#track > *::-webkit-scrollbar-thumb { background: var(--line-2); border-radius: 99px; }
#track > *::-webkit-scrollbar-track { background: transparent; }

/* 页内内容纵向居中；内容超屏时自动回到顶部并可滚动（margin auto 不会裁掉顶部） */
#track > * > .wrap { margin-block: auto; width: 100%; }

/* 横排时不要竖向布局遗留的分隔上边框 */
#track > .section, .section + .section { border-top: none; }

/* 翻页箭头 */
.pgnav {
  position: fixed; top: 50%; transform: translateY(-50%); z-index: 85;
  width: 48px; height: 48px; border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  font-family: var(--serif); font-size: 1.7rem; line-height: 1;
  color: var(--coral-deep); cursor: pointer;
  background: color-mix(in srgb, var(--paper-card) 82%, transparent);
  border: 1px solid var(--line-2); backdrop-filter: blur(8px) saturate(1.1);
  box-shadow: var(--shadow-md);
  transition: transform .18s, background .18s, border-color .18s, opacity .2s, color .18s;
}
.pgnav:hover { background: var(--coral); color: #fff; border-color: var(--coral); transform: translateY(-50%) scale(1.07); }
.pgnav.prev { left: clamp(8px, 1.6vw, 22px); }
.pgnav.next { right: clamp(8px, 1.6vw, 22px); }
.pgnav:disabled { opacity: 0; pointer-events: none; }

/* 页码指示 */
#pgcount {
  position: fixed; z-index: 85; left: 50%; bottom: 16px; transform: translateX(-50%);
  display: flex; align-items: center; gap: .5em;
  font-size: .82rem; font-weight: 700; letter-spacing: .06em;
  font-variant-numeric: tabular-nums; color: var(--ink-2);
  background: color-mix(in srgb, var(--paper-card) 82%, transparent);
  border: 1px solid var(--line); backdrop-filter: blur(8px);
  padding: .4em 1em; border-radius: 99px; box-shadow: var(--shadow-sm);
}
#pgcount #pgnow { color: var(--coral-deep); }
#pgcount .pgsep { color: var(--ink-faint); }

/* 「本页更多」下滑提示 */
#scrollHint {
  position: fixed; z-index: 84; left: 50%; bottom: 54px; transform: translateX(-50%);
  display: inline-flex; align-items: center; gap: .4em;
  font: inherit; font-size: .76rem; font-weight: 600; color: var(--ink-3);
  background: color-mix(in srgb, var(--paper-card) 78%, transparent);
  border: 1px solid var(--line); border-radius: 99px; padding: .35em .9em;
  cursor: pointer; box-shadow: var(--shadow-sm);
  opacity: 0; pointer-events: none; transition: opacity .3s;
}
#scrollHint.show { opacity: 1; pointer-events: auto; }
#scrollHint .sh-arrow { font-size: 1.15em; line-height: 1; animation: shbob 1.4s ease-in-out infinite; }
@keyframes shbob { 0%,100% { transform: translateY(-1px); } 50% { transform: translateY(2px); } }

@media (max-width: 560px) {
  .pgnav { width: 40px; height: 40px; font-size: 1.4rem; opacity: .85; }
  #pgcount { bottom: 12px; }
  #scrollHint { bottom: 46px; }
}
@media (prefers-reduced-motion: reduce) {
  #track { scroll-behavior: auto; }
  #scrollHint .sh-arrow { animation: none; }
}