/* ==========================================================================
   萤火课堂 · 网页版
   设计取自 App 的 DSColors / DSTypography：
   纯白底、品牌黄 #FFC800、中性灰文字、厚描边圆角卡片、无阴影。
   ========================================================================== */

:root {
  --bg: #ffffff;
  --soft: #f7f7f7;
  --soft-2: #fbfbfb;
  --line: #e5e5e5;
  --line-2: #d2d2d2;
  --ink: #3c3c3c;
  --ink-2: #5c5c5c;
  --ink-3: #8a8a8a;
  --muted: #afafaf;

  --primary: #ffc800;
  --primary-soft: #fff8de;
  --on-primary: #3f3720;
  --accent: #b87700;

  --blue: #1cb0f6;
  --purple: #ce82ff;
  --pink: #ff86d0;
  --orange: #ff9600;
  --red: #ff4b4b;
  --green: #58cc02;
  --yellow: #ffd900;

  --radius: 18px;
  --radius-lg: 22px;
  --font-round: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB",
    "Microsoft YaHei", "Helvetica Neue", sans-serif;
  --font-serif: "Songti SC", "STSongti-SC-Bold", "Noto Serif SC", "Source Han Serif SC",
    Georgia, serif;
  --spring: cubic-bezier(0.32, 0.72, 0, 1);
}

* { box-sizing: border-box; -webkit-tap-highlight-color: transparent; }

/* 任何元素带 hidden 都必须真正隐藏（否则自定义 display 会盖掉浏览器默认规则） */
[hidden] { display: none !important; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font-round);
  font-size: 16px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

button, input, textarea { font-family: inherit; font-size: inherit; color: inherit; }
button { cursor: pointer; }
a { color: var(--accent); }

.app {
  max-width: 860px;
  margin: 0 auto;
  padding: 0 20px 64px;
  min-height: 100vh;
}

/* ---------- 顶栏 ---------- */
.topbar {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 60px;
  background: rgba(255, 255, 255, 0.94);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--line);
  margin: 0 -20px;
  padding: 0 20px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 9px;
  background: none;
  border: 0;
  padding: 0;
}

.brand-flame {
  width: 28px;
  height: 28px;
  border-radius: 9px;
  background: var(--primary);
  display: grid;
  place-items: center;
}
.brand-flame svg { width: 17px; height: 17px; display: block; }

.brand-name {
  font-family: var(--font-serif);
  font-size: 19px;
  font-weight: 700;
  letter-spacing: 0.5px;
}

.topbar-right { display: flex; align-items: center; gap: 10px; }

.mode-badge {
  font-size: 12px;
  font-weight: 700;
  color: var(--accent);
  background: var(--primary-soft);
  border: 1px solid #f0d998;
  border-radius: 999px;
  padding: 3px 9px;
}

.icon-btn {
  width: 36px;
  height: 36px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: #fff;
  color: var(--ink-2);
}
.icon-btn:active { background: var(--soft); }

.cards-btn { position: relative; }
.count-badge {
  position: absolute;
  top: -5px;
  right: -5px;
  min-width: 17px;
  height: 17px;
  padding: 0 4px;
  border-radius: 999px;
  border: 1.5px solid #fff;
  background: var(--primary);
  color: var(--on-primary);
  font-size: 10.5px;
  font-weight: 900;
  display: grid;
  place-items: center;
}

/* ---------- 知识卡片 ---------- */
.cards-sub { color: var(--ink-3); font-size: 13px; margin: -8px 0 16px; }
.cards-course { margin-top: 24px; }
.cards-course h2 { font-family: var(--font-serif); font-size: 19px; margin: 0 0 2px; }
.cards-lesson { font-size: 12.5px; color: var(--ink-3); margin: 12px 0 8px; }
.cards-grid { display: grid; gap: 10px; }

.kc-card {
  border: 1.5px solid var(--line);
  border-radius: 16px;
  padding: 15px 16px;
  background: #fff;
}
.kc-card .kc-title { font-family: var(--font-serif); font-size: 17px; margin: 0 0 8px; }
.kc-points { margin: 0; padding-left: 18px; color: var(--ink-2); font-size: 14px; line-height: 1.8; }
.kc-points li { margin: 2px 0; }
.kc-example {
  margin: 10px 0 0;
  padding: 8px 10px;
  background: var(--primary-soft);
  border-radius: 10px;
  font-size: 13px;
  color: var(--ink-2);
}
.kc-meta { font-size: 11.5px; color: var(--muted); margin: 0 0 4px; }
.kc-loading { font-size: 13px; color: var(--ink-3); padding: 10px 0; }
.kc-error { font-size: 13px; color: var(--red); margin: 8px 0 0; }
.quiz-cards { margin-top: 16px; display: grid; gap: 10px; }
.kc-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  margin-top: 18px;
  font-size: 13px;
  font-weight: 800;
  color: var(--ink-2);
}

/* ---------- 屏幕切换 ---------- */
.screen { animation: fadeUp 0.28s var(--spring); }
.screen[hidden] { display: none; }

@keyframes fadeUp {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: none; }
}

/* ---------- 首页 ---------- */
.hero { padding: 34px 0 20px; }

.eyebrow {
  margin: 0 0 8px;
  font-size: 13px;
  font-weight: 800;
  letter-spacing: 2px;
  color: var(--accent);
  text-transform: uppercase;
}

.hero-title {
  font-family: var(--font-serif);
  font-size: clamp(28px, 6vw, 40px);
  line-height: 1.25;
  margin: 0 0 10px;
  letter-spacing: 1px;
}

.hero-sub { margin: 0; color: var(--ink-3); font-size: 15px; }

.ask-card {
  border: 1.5px solid var(--line);
  border-radius: var(--radius-lg);
  padding: 18px;
  background: #fff;
  margin-top: 6px;
}

.field-label {
  display: block;
  font-size: 13px;
  font-weight: 800;
  color: var(--ink-2);
  margin-bottom: 8px;
}

.goal-input {
  width: 100%;
  resize: vertical;
  min-height: 84px;
  border: 1.5px solid var(--line);
  border-radius: 14px;
  padding: 13px 14px;
  background: var(--soft-2);
  outline: none;
  transition: border-color 0.15s, background 0.15s;
  line-height: 1.6;
}
.goal-input:focus { border-color: var(--primary); background: #fff; }
.goal-input::placeholder { color: var(--muted); }

.chips { display: flex; flex-wrap: wrap; gap: 8px; margin: 12px 0 4px; }

.chip {
  border: 1px solid var(--line);
  background: #fff;
  border-radius: 999px;
  padding: 6px 13px;
  font-size: 13px;
  color: var(--ink-2);
  font-weight: 600;
  transition: transform 0.12s var(--spring), border-color 0.12s;
}
.chip:hover { border-color: var(--primary); }
.chip:active { transform: scale(0.96); }

.duration-row { margin-top: 18px; }

.segmented {
  display: inline-flex;
  gap: 4px;
  padding: 4px;
  background: var(--soft);
  border-radius: 14px;
}

.segmented button {
  border: 0;
  background: transparent;
  padding: 8px 20px;
  border-radius: 11px;
  font-size: 14px;
  font-weight: 700;
  color: var(--ink-3);
  transition: background 0.15s, color 0.15s;
}
.segmented button.active {
  background: var(--primary);
  color: var(--on-primary);
}

.duration-note {
  margin: 9px 0 0;
  font-size: 13px;
  color: var(--ink-3);
}

/* ---------- 按钮 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  border-radius: 14px;
  border: 1px solid var(--line-2);
  padding: 12px 20px;
  font-size: 15px;
  font-weight: 800;
  background: #fff;
  color: var(--ink);
  transition: transform 0.12s var(--spring), filter 0.15s, background 0.15s;
  user-select: none;
}
.btn:active { transform: translateY(1px) scale(0.995); }
.btn:disabled { opacity: 0.5; cursor: not-allowed; }

.btn-primary {
  background: var(--primary);
  border-color: #e5b100;
  border-bottom-width: 3px;
  color: var(--on-primary);
}
.btn-primary:hover { filter: brightness(1.03); }

.btn-ghost { background: #fff; border-color: var(--line); color: var(--ink-2); }
.btn-ghost:hover { background: var(--soft); }

.btn-block { width: 100%; margin-top: 18px; padding: 14px 20px; font-size: 16px; }
.btn-small { padding: 9px 16px; font-size: 14px; border-radius: 11px; }

.fineprint {
  margin: 12px 0 0;
  font-size: 12px;
  color: var(--muted);
  text-align: center;
}

.link-btn {
  border: 0;
  background: none;
  color: var(--accent);
  font-weight: 700;
  font-size: 14px;
  padding: 4px;
}

/* ---------- 课程列表 ---------- */
.section { margin-top: 30px; }
.section-head { display: flex; align-items: center; justify-content: space-between; }
.section-head h2 {
  font-family: var(--font-serif);
  font-size: 20px;
  margin: 0 0 12px;
}

.course-list { display: grid; gap: 12px; }

.course-item { display: flex; align-items: center; gap: 8px; }
.course-item .course-card { flex: 1; min-width: 0; }

.course-del {
  flex: 0 0 auto;
  width: 42px;
  height: 42px;
  border-radius: 12px;
  border: 1.5px solid var(--line);
  background: #fff;
  color: var(--ink-3);
  display: grid;
  place-items: center;
  transition: border-color 0.15s, color 0.15s, background 0.15s;
}
.course-del:hover { border-color: var(--red); color: var(--red); background: #fff6f5; }
.course-del:active { transform: scale(0.96); }

.course-card {
  display: flex;
  align-items: center;
  gap: 14px;
  border: 1.5px solid var(--line);
  border-radius: var(--radius);
  padding: 14px 16px;
  background: #fff;
  text-align: left;
  transition: border-color 0.15s, transform 0.15s var(--spring);
}
.course-card:hover { border-color: var(--primary); }
.course-card:active { transform: scale(0.99); }

.course-orb {
  flex: 0 0 auto;
  width: 44px;
  height: 44px;
  border-radius: 14px;
  display: grid;
  place-items: center;
  font-size: 20px;
  background: var(--primary-soft);
}

.course-card-main { flex: 1; min-width: 0; }
.course-card-title {
  margin: 0;
  font-size: 15.5px;
  font-weight: 800;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.course-card-meta { margin: 2px 0 0; font-size: 12.5px; color: var(--ink-3); }

.mini-progress {
  flex: 0 0 44px;
  font-size: 12px;
  font-weight: 800;
  color: var(--accent);
  text-align: right;
}

/* ---------- 页脚 ---------- */
.footer {
  margin-top: 40px;
  padding-top: 18px;
  border-top: 1px solid var(--line);
  text-align: center;
}
.footer-ai { font-size: 12px; color: var(--muted); margin: 0 0 10px; }
.footer-links {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 6px 16px;
  margin-bottom: 10px;
}
.footer-links button {
  border: 0;
  background: none;
  color: var(--ink-3);
  font-size: 12.5px;
  padding: 2px;
}
.footer-links button:hover { color: var(--accent); }
.footer-icp { font-size: 12px; margin: 0; }
.footer-icp a { color: var(--ink-3); text-decoration: none; }

/* ---------- 生成中 ---------- */
.gen-wrap {
  padding: 70px 10px 40px;
  text-align: center;
  max-width: 460px;
  margin: 0 auto;
}

.flame-loader {
  width: 74px;
  height: 74px;
  margin: 0 auto 26px;
  border-radius: 24px;
  background: var(--primary);
  display: grid;
  place-items: center;
  animation: breathe 1.6s var(--spring) infinite;
}
.flame-loader span {
  width: 26px;
  height: 34px;
  background: #fff;
  clip-path: polygon(50% 0, 82% 34%, 76% 58%, 100% 62%, 84% 100%, 16% 100%, 0 62%, 24% 58%, 18% 34%);
}
@keyframes breathe {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.07); }
}

.gen-title { font-family: var(--font-serif); font-size: 24px; margin: 0 0 8px; }
.gen-sub { color: var(--ink-3); font-size: 14px; margin: 0 0 30px; }

.gen-stages { display: grid; gap: 10px; text-align: left; }
.gen-stage {
  display: flex;
  gap: 12px;
  align-items: flex-start;
  padding: 13px 15px;
  border: 1.5px solid var(--line);
  border-radius: 14px;
  color: var(--ink-3);
  transition: border-color 0.25s, background 0.25s, color 0.25s;
}
.gen-stage .dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--line-2);
  margin-top: 7px;
  flex: 0 0 auto;
  transition: background 0.25s;
}
.gen-stage strong { display: block; font-size: 14.5px; }
.gen-stage em { display: block; font-style: normal; font-size: 12.5px; margin-top: 2px; }
.gen-stage.active { border-color: var(--primary); background: var(--primary-soft); color: var(--ink); }
.gen-stage.active .dot { background: var(--primary); animation: pulse 1s infinite; }
.gen-stage.done { border-color: var(--line); color: var(--ink-2); }
.gen-stage.done .dot { background: var(--green); }
@keyframes pulse { 50% { transform: scale(1.45); opacity: 0.65; } }

.gen-elapsed { margin: 18px 0 10px; font-size: 13px; color: var(--muted); }

/* ---------- 目录预览 ---------- */
.back-btn {
  border: 0;
  background: none;
  color: var(--ink-3);
  font-size: 14px;
  font-weight: 700;
  padding: 16px 0 6px;
}

.plan-head { padding: 6px 0 4px; }
.plan-meta { display: flex; gap: 8px; margin-bottom: 10px; }

.tag {
  display: inline-block;
  background: var(--primary);
  color: var(--on-primary);
  font-size: 12px;
  font-weight: 800;
  padding: 3px 10px;
  border-radius: 999px;
}
.tag-soft { background: var(--soft); color: var(--ink-3); border: 1px solid var(--line); }

.plan-title { font-family: var(--font-serif); font-size: 28px; margin: 0 0 10px; line-height: 1.3; }
.plan-intro { margin: 0; color: var(--ink-2); font-size: 14.5px; }
.plan-stats { margin: 10px 0 0; font-size: 13px; color: var(--ink-3); }

.plan-chapters { margin-top: 22px; display: grid; gap: 10px; }

.chapter-card {
  border: 1.5px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  background: #fff;
}
.chapter-head {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 14px 16px;
  background: var(--soft-2);
}
.chapter-index {
  width: 26px;
  height: 26px;
  flex: 0 0 auto;
  border-radius: 9px;
  background: var(--primary);
  color: var(--on-primary);
  display: grid;
  place-items: center;
  font-size: 12.5px;
  font-weight: 900;
}
.chapter-title { margin: 0; font-size: 15px; font-weight: 800; flex: 1; }
.chapter-count { font-size: 12px; color: var(--ink-3); }
.chapter-lessons { margin: 0; padding: 6px 16px 12px; list-style: none; }
.chapter-lessons li {
  display: flex;
  gap: 9px;
  padding: 7px 0;
  font-size: 14px;
  color: var(--ink-2);
  border-top: 1px solid var(--soft);
}
.chapter-lessons li:first-child { border-top: 0; }
.lesson-dot { color: var(--line-2); font-weight: 900; }

.plan-feedback {
  margin-top: 26px;
  border: 1.5px solid var(--line);
  border-radius: var(--radius);
  padding: 16px;
}
.plan-feedback textarea {
  width: 100%;
  resize: vertical;
  border: 1.5px solid var(--line);
  border-radius: 12px;
  padding: 11px 13px;
  background: var(--soft-2);
  outline: none;
}
.plan-feedback textarea:focus { border-color: var(--primary); background: #fff; }
.feedback-actions { display: flex; gap: 10px; margin-top: 12px; }
.feedback-actions .btn { flex: 1; }

/* ---------- 课程详情 ---------- */
.course-head { padding: 6px 0 8px; }
.course-title { font-family: var(--font-serif); font-size: 27px; margin: 0 0 8px; line-height: 1.3; }
.course-sub { margin: 0 0 16px; color: var(--ink-3); font-size: 14px; }

.progress-row { display: flex; align-items: center; gap: 10px; margin-bottom: 16px; }
.progress {
  flex: 1;
  height: 12px;
  border-radius: 999px;
  background: var(--soft);
  overflow: hidden;
}
.progress span {
  display: block;
  height: 100%;
  width: 0;
  border-radius: 999px;
  background: var(--primary);
  transition: width 0.5s var(--spring);
}
.progress-row strong { font-size: 13px; color: var(--accent); }

.course-chapters { margin-top: 20px; display: grid; gap: 12px; }

.lesson-row {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 11px 12px;
  border-radius: 12px;
  border: 1px solid transparent;
  background: none;
  width: 100%;
  text-align: left;
  font-size: 14px;
  color: var(--ink-2);
}
.lesson-row:hover { background: var(--soft-2); }
.lesson-row .status {
  width: 20px;
  height: 20px;
  border-radius: 50%;
  border: 2px solid var(--line-2);
  display: grid;
  place-items: center;
  font-size: 11px;
  color: #fff;
  flex: 0 0 auto;
}
.lesson-row.done .status { background: var(--green); border-color: var(--green); }
.lesson-row.active .status { border-color: var(--primary); background: var(--primary); }
.lesson-row.done { color: var(--ink-3); }
.lesson-row.current { background: var(--primary-soft); }

/* ---------- 上课（苏格拉底式对话） ---------- */
.lesson-head { padding-top: 8px; }
.lesson-kicker { font-size: 12.5px; color: var(--ink-3); margin: 0 0 6px; }
.lesson-title { font-family: var(--font-serif); font-size: 26px; line-height: 1.35; margin: 0 0 8px; }
.lesson-hint { margin: 0 0 12px; color: var(--ink-3); font-size: 13px; }

.teach-log {
  display: flex;
  flex-direction: column;
  gap: 16px;
  padding: 6px 0 18px;
  min-height: 220px;
}
.teach-log .chat-msg { max-width: 94%; }
.teach-log .bubble { font-size: 15.5px; line-height: 1.85; }
.teach-log .bubble p { margin: 0 0 10px; }
.teach-log .bubble p:last-child { margin-bottom: 0; }
.teach-log .bubble h2 { font-family: var(--font-serif); font-size: 18px; margin: 14px 0 8px; }
.teach-log .bubble h3 { font-size: 16px; margin: 12px 0 6px; }
.teach-log .bubble ul, .teach-log .bubble ol { padding-left: 22px; margin: 0 0 10px; }
.teach-log .bubble li { margin: 3px 0; }
.teach-log .bubble strong { background: linear-gradient(transparent 62%, var(--primary-soft) 62%); }
.teach-log .bubble blockquote {
  margin: 12px 0;
  padding: 10px 13px;
  background: #fff;
  border-left: 3px solid var(--line-2);
  border-radius: 0 10px 10px 0;
  color: var(--ink-2);
}
.teach-log .bubble code {
  background: var(--soft);
  padding: 2px 6px;
  border-radius: 6px;
  font-size: 0.9em;
  font-family: "SF Mono", Menlo, Consolas, monospace;
}
.teach-log .bubble pre {
  background: #2f2f2f;
  color: #f4f4f4;
  padding: 12px 14px;
  border-radius: 12px;
  overflow-x: auto;
  font-size: 13.5px;
  line-height: 1.6;
}
.teach-log .bubble pre code { background: none; padding: 0; color: inherit; }

/* 分数与根号（提示词要求 \frac、\sqrt，这里渲染成真正的上下分式） */
.frac {
  display: inline-flex;
  flex-direction: column;
  vertical-align: middle;
  text-align: center;
  font-size: 0.92em;
  margin: 0 2px;
  line-height: 1.25;
}
.frac .num { border-bottom: 1px solid currentColor; padding: 0 4px; }
.frac .den { padding: 0 4px; }
.sqrt { white-space: nowrap; }
.sqrt .radical { border-top: 1px solid currentColor; padding: 0 3px; }

.teach-form {
  position: sticky;
  bottom: 0;
  z-index: 5;
  display: flex;
  align-items: flex-end;
  gap: 8px;
  padding: 10px 0 calc(10px + env(safe-area-inset-bottom));
  background: linear-gradient(to top, #fff 80%, rgba(255, 255, 255, 0));
  border-top: 1px solid var(--line);
}
.teach-form textarea {
  flex: 1;
  min-height: 44px;
  max-height: 42vh;
  resize: none;
  overflow-y: auto;
  border: 1.5px solid var(--line);
  border-radius: 12px;
  padding: 11px 13px;
  outline: none;
  background: var(--soft-2);
  font-family: inherit;
  font-size: 15px;
  line-height: 1.6;
}
.teach-form textarea:focus { border-color: var(--primary); background: #fff; }
.teach-form textarea:disabled { opacity: 0.6; }
.teach-form.hidden { display: none; }

.lesson-actions {
  display: flex;
  gap: 10px;
  margin: 8px 0 16px;
}
.lesson-actions .btn { flex: 1; }

.lesson-done-note {
  text-align: center;
  font-size: 13px;
  color: var(--green);
  font-weight: 700;
  margin: 4px 0 20px;
}

/* ---------- 随堂测 ---------- */
.quiz-head { padding: 8px 0 14px; }
.quiz-title { font-family: var(--font-serif); font-size: 24px; margin: 8px 0 0; }

.quiz-card {
  border: 1.5px solid var(--line);
  border-radius: var(--radius);
  padding: 20px 18px;
}
.quiz-question { font-size: 17px; font-weight: 700; line-height: 1.6; margin: 0 0 16px; }
.quiz-options { display: grid; gap: 10px; }
.quiz-option {
  display: flex;
  align-items: center;
  gap: 11px;
  text-align: left;
  border: 1.5px solid var(--line);
  border-radius: 13px;
  background: #fff;
  padding: 12px 14px;
  font-size: 15px;
  transition: border-color 0.15s, background 0.15s;
}
.quiz-option:hover { border-color: var(--line-2); }
.quiz-option .key {
  width: 24px;
  height: 24px;
  border-radius: 8px;
  background: var(--soft);
  display: grid;
  place-items: center;
  font-size: 12px;
  font-weight: 800;
  color: var(--ink-3);
  flex: 0 0 auto;
}
.quiz-option.correct { border-color: var(--green); background: #f4fbe9; }
.quiz-option.correct .key { background: var(--green); color: #fff; }
.quiz-option.wrong { border-color: var(--red); background: #fff3f2; }
.quiz-option.wrong .key { background: var(--red); color: #fff; }
.quiz-option:disabled { cursor: default; }

.quiz-explain {
  margin: 16px 0 0;
  background: var(--soft-2);
  border-radius: 12px;
  padding: 12px 14px;
  font-size: 14px;
  color: var(--ink-2);
}
.quiz-foot { display: flex; gap: 10px; margin-top: 16px; }
.quiz-foot .btn { flex: 1; }
.quiz-result { text-align: center; padding: 12px 0 4px; }
.quiz-result .big { font-family: var(--font-serif); font-size: 30px; display: block; margin-bottom: 6px; }

/* ---------- 我的课程 ---------- */
.library-title { font-family: var(--font-serif); font-size: 26px; margin: 8px 0 16px; }
.empty-note { color: var(--ink-3); font-size: 14px; text-align: center; padding: 50px 0; }

/* ---------- 对话抽屉 ---------- */
.drawer-mask {
  position: fixed;
  inset: 0;
  background: rgba(40, 36, 24, 0.28);
  z-index: 40;
  animation: fadeIn 0.2s ease;
}
@keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }

.drawer {
  position: fixed;
  z-index: 41;
  right: 0;
  top: 0;
  bottom: 0;
  width: min(440px, 100%);
  background: #fff;
  border-left: 1px solid var(--line);
  display: flex;
  flex-direction: column;
  animation: slideIn 0.32s var(--spring);
}
@keyframes slideIn { from { transform: translateX(30px); opacity: 0; } to { transform: none; opacity: 1; } }

.drawer-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 18px;
  border-bottom: 1px solid var(--line);
}
.drawer-head strong { font-size: 16px; }
.drawer-sub { display: block; font-size: 12px; color: var(--ink-3); margin-top: 2px; }

.chat-log {
  flex: 1;
  overflow-y: auto;
  padding: 16px 18px;
  display: flex;
  flex-direction: column;
  gap: 12px;
}
.chat-msg { max-width: 88%; font-size: 14.5px; line-height: 1.7; }
.chat-msg.ai { align-self: flex-start; }
.chat-msg.user { align-self: flex-end; }
.chat-msg .bubble {
  padding: 11px 14px;
  border-radius: 15px;
  white-space: pre-wrap;
  word-break: break-word;
}
.chat-msg.ai .bubble { background: var(--soft); border-top-left-radius: 5px; }
.chat-msg .ai-label {
  display: block;
  font-size: 10.5px;
  color: var(--muted);
  margin-top: 4px;
  padding-left: 2px;
}
.chat-msg.user .bubble { background: var(--primary); color: var(--on-primary); border-top-right-radius: 5px; }
.chat-msg .typing { display: inline-flex; gap: 4px; padding: 6px 2px; }
.chat-msg .typing i { width: 6px; height: 6px; border-radius: 50%; background: var(--muted); animation: blink 1.2s infinite; }
.chat-msg .typing i:nth-child(2) { animation-delay: 0.18s; }
.chat-msg .typing i:nth-child(3) { animation-delay: 0.36s; }
@keyframes blink { 0%, 80%, 100% { opacity: 0.3; } 40% { opacity: 1; } }

.chat-form {
  display: flex;
  gap: 8px;
  padding: 12px 16px 4px;
  border-top: 1px solid var(--line);
}
.chat-form input {
  flex: 1;
  border: 1.5px solid var(--line);
  border-radius: 12px;
  padding: 10px 13px;
  outline: none;
  background: var(--soft-2);
}
.chat-form input:focus { border-color: var(--primary); background: #fff; }
.chat-note { text-align: center; font-size: 11.5px; color: var(--muted); margin: 6px 0 12px; }

/* ---------- 文档弹层 ---------- */
.modal-mask {
  position: fixed;
  inset: 0;
  z-index: 50;
  background: rgba(40, 36, 24, 0.3);
  display: grid;
  place-items: center;
  padding: 20px;
}
.modal {
  width: min(620px, 100%);
  max-height: 82vh;
  background: #fff;
  border-radius: 20px;
  border: 1.5px solid var(--line);
  display: flex;
  flex-direction: column;
  animation: fadeUp 0.26s var(--spring);
}
.modal-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 20px;
  border-bottom: 1px solid var(--line);
}
.modal-head h2 { font-family: var(--font-serif); font-size: 19px; margin: 0; }
.modal-body { padding: 18px 20px 22px; overflow-y: auto; font-size: 14.5px; color: var(--ink-2); }
.modal-small { width: min(400px, 100%); }
.modal-small .modal-body { padding-bottom: 8px; }
.modal-foot { display: flex; gap: 10px; padding: 0 20px 20px; }
.modal-foot .btn { flex: 1; }
.confirm-warn { font-size: 12.5px; color: var(--ink-3); margin: 8px 0 0; }

.btn-danger {
  background: var(--red);
  border-color: #e53b3b;
  border-bottom-width: 3px;
  color: #fff;
}
.btn-danger:hover { filter: brightness(1.04); }
.modal-body h3 { font-size: 15px; margin: 18px 0 6px; color: var(--ink); }
.modal-body p { margin: 0 0 10px; }
.modal-body ul { padding-left: 20px; margin: 0 0 12px; }

/* ---------- Toast ---------- */
.toast {
  position: fixed;
  left: 50%;
  bottom: 34px;
  transform: translateX(-50%);
  background: #2f2f2f;
  color: #fff;
  font-size: 13.5px;
  padding: 10px 18px;
  border-radius: 999px;
  z-index: 60;
  animation: fadeUp 0.24s var(--spring);
}

/* ---------- 桌面适配 ---------- */
@media (min-width: 720px) {
  .course-list { grid-template-columns: 1fr 1fr; }
  .cards-grid { grid-template-columns: 1fr 1fr; }
  .plan-chapters { grid-template-columns: 1fr 1fr; align-items: start; }
  .course-chapters { grid-template-columns: 1fr 1fr; align-items: start; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation: none !important; transition: none !important; }
}