/* ===== DDIA 白話讀本 — 書冊風格 =====
   紙白 / 墨青 / 靛青主色 / 朱砂只用於印章 */
:root {
  --paper: #FAF9F6;        /* 紙 */
  --paper-deep: #F2F0EA;   /* 襯頁 */
  --ink: #212B36;          /* 墨 */
  --ink-dim: #77839A;      /* 淡墨 */
  --indigo: #34558B;       /* 靛青（主色） */
  --indigo-soft: #E9EEF6;
  --seal: #B5342C;         /* 朱砂（印章專用） */
  --seal-soft: #F7E9E7;
  --ok: #4A7C59;
  --ok-soft: #EAF1EC;
  --line: #DDD9CE;         /* 髮絲線 */
  --line-strong: #C8C3B4;
  --maxw: 43em;

  --serif: "Noto Serif TC", "Source Han Serif TC", "Songti TC", "PMingLiU", serif;
  --sans: "Noto Sans TC", "PingFang TC", "Microsoft JhengHei", system-ui, sans-serif;
  --kai: "Kaiti TC", "DFKai-SB", "BiauKai", "標楷體", var(--serif);
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 17px;
  line-height: 1.95;
  letter-spacing: .015em;
}
#app { max-width: var(--maxw); margin: 0 auto; padding: 0 22px 96px; }
.view { animation: page-in .45s ease both; }
@keyframes page-in { from { opacity: 0; transform: translateY(6px); } to { opacity: 1; transform: none; } }
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation: none !important; transition: none !important; }
}

.loading { text-align: center; color: var(--ink-dim); padding: 80px 0; font-family: var(--serif); }
a { color: var(--indigo); text-underline-offset: 3px; }
code {
  font-family: ui-monospace, "Cascadia Code", Consolas, monospace;
  font-size: .86em;
  background: var(--paper-deep);
  border-radius: 4px;
  padding: 1px 6px;
}
button { font-family: var(--sans); font-size: 15px; cursor: pointer; color: var(--ink); }
button:focus-visible, a:focus-visible { outline: 2px solid var(--indigo); outline-offset: 2px; }

/* ===== 首頁：書封 ===== */
.cover {
  position: relative;
  display: flex; align-items: stretch; gap: 26px;
  padding: 58px 6px 40px;
  border-bottom: 1px solid var(--line);
}
.cover-spine {
  writing-mode: vertical-rl;
  font-family: var(--serif);
  font-size: 14px; letter-spacing: .34em; color: var(--ink-dim);
  border-right: 1px solid var(--line);
  padding-right: 16px;
}
.cover-main { flex: 1; }
.cover-sub em { font-style: normal; letter-spacing: .04em; }
.cover-eyebrow {
  font-size: 12.5px; letter-spacing: .3em; color: var(--indigo);
  margin-bottom: 14px;
}
.cover-title {
  margin: 0;
  font-family: var(--serif); font-weight: 900;
  font-size: 42px; line-height: 1.25; letter-spacing: .06em;
}
.cover-sub {
  margin: 14px 0 0; color: var(--ink-dim); font-size: 14px; line-height: 1.9;
}
.cover-seal {
  position: absolute; right: 10px; top: 62px;
  width: 58px; height: 58px;
  display: grid; place-items: center;
  background: var(--seal); color: #FBF6F0;
  font-family: var(--serif); font-weight: 700; font-size: 19px;
  line-height: 1.15; text-align: center; letter-spacing: .08em;
  border-radius: 6px;
  transform: rotate(-3deg);
  box-shadow: inset 0 0 0 2px rgba(251, 246, 240, .55), inset 0 0 0 4px var(--seal);
}

/* ===== 書籤（續讀） ===== */
.resume-card {
  display: flex; align-items: center; gap: 16px;
  width: 100%; text-align: left;
  margin: 30px 0 4px; padding: 15px 18px 15px 22px;
  background: var(--indigo-soft);
  border: none; border-left: 4px solid var(--indigo);
  border-radius: 0 8px 8px 0;
  transition: background .2s;
}
.resume-card:hover { background: #E0E8F3; }
.resume-card .rc-label {
  writing-mode: vertical-rl; flex: none;
  font-family: var(--serif); font-size: 12px; letter-spacing: .3em;
  color: var(--indigo);
  border-right: 1px solid rgba(52, 85, 139, .25); padding-right: 10px;
}
.resume-card .rc-title { font-size: 16px; font-weight: 500; line-height: 1.7; }
.resume-card .rc-title strong { font-family: var(--serif); }

/* ===== 目錄 ===== */
.overall {
  margin: 34px 0 6px; font-size: 12.5px; letter-spacing: .2em; color: var(--ink-dim);
  display: flex; align-items: baseline; gap: 14px;
  font-family: var(--serif);
}
.overall .bar { flex: 1; height: 1px; background: var(--line); position: relative; }
.overall .bar i {
  position: absolute; left: 0; top: -1px; height: 3px;
  background: var(--indigo); transition: width .4s;
}
.chapter-list { list-style: none; margin: 6px 0 0; padding: 0; }
.chapter-row {
  display: flex; align-items: baseline; gap: 12px;
  width: 100%; text-align: left;
  padding: 15px 6px;
  background: none; border: none; border-bottom: 1px solid var(--line);
  font-size: 16px; line-height: 1.6;
  transition: background .15s;
}
.chapter-row:hover { background: var(--paper-deep); }
.chapter-row .cc-num {
  flex: none; width: 4.6em;
  font-family: var(--serif); font-size: 13.5px; letter-spacing: .12em;
  color: var(--indigo);
}
.chapter-row .cc-title { font-family: var(--serif); font-weight: 700; letter-spacing: .04em; }
.chapter-row .leader {
  flex: 1; min-width: 20px;
  border-bottom: 1px dotted var(--line-strong);
  transform: translateY(-4px);
}
.chapter-row .cc-status { flex: none; font-size: 12.5px; color: var(--ink-dim); }
.seal-mini {
  display: inline-grid; place-items: center;
  width: 34px; height: 20px;
  background: var(--seal); color: #FBF6F0;
  font-family: var(--serif); font-size: 11px; letter-spacing: .15em;
  border-radius: 3px; transform: rotate(-2deg);
}
.about {
  margin-top: 44px; padding-top: 18px;
  border-top: 1px solid var(--line);
  font-size: 12.5px; color: var(--ink-dim); line-height: 2;
}

/* ===== 章節頁 ===== */
.ch-nav {
  position: sticky; top: 0; z-index: 10;
  display: flex; align-items: center; gap: 12px;
  margin: 0 -22px 8px; padding: 13px 22px;
  background: color-mix(in srgb, var(--paper) 90%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line);
}
.ch-nav .back {
  background: none; border: none; color: var(--indigo);
  font-size: 14px; letter-spacing: .1em; padding: 4px 6px;
}
.ch-nav .ch-nav-title {
  flex: 1; font-family: var(--serif); font-size: 13.5px; letter-spacing: .08em;
  color: var(--ink-dim);
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
}

.ch-header { padding: 44px 0 8px; text-align: center; }
.ch-header .ch-no {
  font-family: var(--serif); font-size: 15px; letter-spacing: .55em; text-indent: .55em;
  color: var(--indigo);
}
.ch-header .ch-no::after {
  content: ''; display: block; width: 34px; height: 1px;
  background: var(--line-strong); margin: 16px auto 0;
}
.ch-header h1 {
  margin: 18px 0 10px;
  font-family: var(--serif); font-weight: 900;
  font-size: 31px; letter-spacing: .08em; line-height: 1.4;
}
.ch-header .subtitle { color: var(--ink-dim); font-size: 12.5px; letter-spacing: .06em; }

/* 開場比喻：楷體引言頁 */
.analogy {
  margin: 34px 0 40px; padding: 26px 26px 22px;
  background: var(--paper-deep);
  border-radius: 8px;
}
.analogy h2 {
  margin: 0 0 10px;
  font-family: var(--serif); font-size: 15px; letter-spacing: .18em;
  color: var(--indigo);
}
.analogy p {
  margin: 12px 0; font-family: var(--kai);
  font-size: 17.5px; line-height: 2.05; color: #3A4350;
}

section.ch-section { margin: 44px 0; scroll-margin-top: 70px; }
section.ch-section h2 {
  font-family: var(--serif); font-weight: 900;
  font-size: 21px; letter-spacing: .05em; line-height: 1.55;
  margin: 0 0 16px; padding-left: 14px;
  border-left: 3px solid var(--indigo);
}
section.ch-section p { margin: 15px 0; text-align: justify; }
section.ch-section strong { color: var(--indigo); font-weight: 700; }

/* 術語卡：辭典條目 */
.terms { margin: 20px 0 4px; border-top: 1px solid var(--line); }
.term-card {
  display: grid; grid-template-columns: 1fr auto 1.15fr; align-items: center; gap: 12px;
  padding: 10px 4px; font-size: 14px;
  border-bottom: 1px solid var(--line);
}
.term-card .plain { color: var(--ink-dim); }
.term-card .arrow { color: var(--line-strong); font-size: 12px; }
.term-card .formal { font-family: var(--serif); font-weight: 700; letter-spacing: .03em; }
.term-card .en {
  display: block; font-family: var(--sans); font-weight: 400;
  font-size: 11.5px; letter-spacing: .04em; color: var(--ink-dim);
}

/* ===== 圖解 ===== */
.diagram {
  margin: 40px 0; padding: 22px 22px 18px;
  background: #FFFFFF;
  border: 1px solid var(--line); border-radius: 10px;
}
.diagram h2 {
  font-family: var(--serif); font-size: 16px; letter-spacing: .1em;
  margin: 0 0 14px;
}
.diagram svg { width: 100%; height: auto; display: block; }
.diagram .dg-caption {
  min-height: 3.4em; margin: 12px 0; padding: 11px 15px;
  font-size: 14.5px; line-height: 1.9;
  background: var(--paper-deep); border-radius: 8px;
}
.diagram .dg-controls { display: flex; gap: 8px; align-items: center; }
.diagram .dg-controls button {
  padding: 7px 18px; border: 1px solid var(--line-strong); border-radius: 6px;
  background: #FFF; letter-spacing: .05em;
}
.diagram .dg-controls button.primary { background: var(--indigo); border-color: var(--indigo); color: #FFF; }
.diagram .dg-controls button:disabled { opacity: .35; cursor: default; }
.diagram .dg-step-ind { margin-left: auto; font-size: 12.5px; color: var(--ink-dim); font-family: var(--serif); }

/* SVG 元素狀態 */
.diagram svg .box { fill: var(--paper-deep); stroke: var(--line-strong); stroke-width: 1.2; rx: 7; transition: all .35s; }
.diagram svg .box.hot { fill: var(--indigo-soft); stroke: var(--indigo); }
.diagram svg .box.good { fill: var(--ok-soft); stroke: var(--ok); }
.diagram svg .box.bad { fill: var(--seal-soft); stroke: var(--seal); }
.diagram svg text { fill: var(--ink); font-size: 13px; font-family: var(--sans); }
.diagram svg text.small { font-size: 11px; fill: var(--ink-dim); }
.diagram svg .arrow { stroke: var(--ink-dim); stroke-width: 1.8; fill: none; marker-end: url(#arrowhead); transition: all .35s; }
.diagram svg .arrow.hot { stroke: var(--indigo); }
.diagram svg .arrow.bad { stroke: var(--seal); }
.diagram svg .ghost { opacity: 0; transition: opacity .35s; }
.diagram svg .ghost.show { opacity: 1; }

/* ===== 練習題 ===== */
.quiz {
  margin: 44px 0; padding: 24px 24px 20px;
  background: #FFFFFF;
  border: 1px solid var(--line); border-radius: 10px;
}
.quiz > h2 {
  font-family: var(--serif); font-size: 18px; letter-spacing: .12em;
  margin: 0 0 4px;
}
.quiz .quiz-sub { font-size: 13px; color: var(--ink-dim); margin: 0 0 16px; }
.quiz-item { margin: 22px 0; }
.quiz-item .qq { font-weight: 700; margin-bottom: 10px; line-height: 1.8; }
.quiz-item .opts { display: grid; gap: 8px; }
.quiz-item .opt {
  text-align: left; padding: 10px 15px; line-height: 1.75;
  background: var(--paper); border: 1px solid var(--line);
  border-radius: 8px; transition: border-color .15s, background .15s;
}
.quiz-item .opt:not(:disabled):hover { border-color: var(--indigo); background: var(--indigo-soft); }
.quiz-item .opt.correct { background: var(--ok-soft); border-color: var(--ok); font-weight: 700; }
.quiz-item .opt.wrong { background: var(--seal-soft); border-color: var(--seal); }
.quiz-item .explain {
  margin-top: 10px; padding: 11px 15px; font-size: 14.5px; line-height: 1.9;
  background: var(--paper-deep); border-radius: 8px;
}
.quiz-item .explain .verdict { font-weight: 700; font-family: var(--serif); }
.quiz-item .explain .verdict.ok { color: var(--ok); }
.quiz-item .explain .verdict.bad { color: var(--seal); }
.quiz-result {
  margin-top: 18px; padding: 13px; text-align: center;
  background: var(--indigo-soft); border-radius: 8px;
  font-family: var(--serif); font-weight: 700; letter-spacing: .1em;
}
.quiz-retry {
  margin-top: 10px; width: 100%; padding: 10px;
  border: 1px solid var(--line-strong); border-radius: 8px; background: #FFF;
}

/* ===== 章末 ===== */
.ch-footer { margin: 46px 0 10px; display: grid; gap: 12px; }
.mark-read {
  display: flex; align-items: center; justify-content: center; gap: 10px;
  padding: 13px; border-radius: 8px; font-size: 15.5px; letter-spacing: .1em;
  border: 1px solid var(--indigo); background: none; color: var(--indigo);
  font-family: var(--serif);
}
.mark-read .seal-mini { animation: stamp .3s ease both; }
@keyframes stamp { from { transform: scale(1.6) rotate(-8deg); opacity: 0; } to { transform: scale(1) rotate(-2deg); opacity: 1; } }
.mark-read.done { border-color: var(--line); color: var(--ink-dim); }
.ch-pager { display: flex; gap: 12px; }
.ch-pager button {
  flex: 1; padding: 12px; border-radius: 8px; letter-spacing: .08em;
  border: 1px solid var(--line); background: none; color: var(--ink);
  font-family: var(--serif);
}
.ch-pager button:not(:disabled):hover { border-color: var(--indigo); color: var(--indigo); }
.ch-pager button:disabled { opacity: .3; }

@media (max-width: 480px) {
  body { font-size: 16px; }
  .cover { padding: 40px 0 32px; gap: 18px; }
  .cover-title { font-size: 32px; }
  .cover-seal { width: 48px; height: 48px; font-size: 16px; }
  .ch-header h1 { font-size: 25px; }
  .term-card { grid-template-columns: 1fr; gap: 2px; }
  .term-card .arrow { display: none; }
}