/* GESP 四级互动课堂 v2 · 科技风单屏递进版
   设计：深空底色 + 霓虹光晕 + 玻璃拟态卡片 + HUD 状态栏
   交互：一屏一个知识点，完成本屏任务才解锁下一屏 */
:root {
  --bg: #060A12;        --bg2: #0A1020;
  --cyan: #22D3EE;      --cyan-d: #0891B2;
  --violet: #A855F7;    --violet-d: #7C3AED;
  --lime: #A3E635;      --lime-d: #65A30D;
  --amber: #FBBF24;     --amber-d: #D97706;
  --pink: #F472B6;      --red: #F87171;
  --txt: #E9F2FF;       --dim: #8CA0BE;   --dim2: #5B6B85;
  --panel: rgba(255,255,255,.045);
  --panel2: rgba(255,255,255,.07);
  --line: rgba(120,200,255,.16);
  --glow: 0 0 24px rgba(34,211,238,.28);
  --mono: Consolas, "JetBrains Mono", "Courier New", monospace;
}
* { box-sizing: border-box; }
html, body { height: 100%; margin: 0; }
body {
  background: var(--bg); color: var(--txt); overflow: hidden;
  font-family: "微软雅黑", "Microsoft YaHei", system-ui, sans-serif; font-size: 16px;
}
/* 背景：网格 + 光晕 + 星点 */
.bg, .bg::before, .bg::after { position: fixed; inset: 0; pointer-events: none; }
/* ★ 性能（kk老师 2026-10-15 报"课件很卡、CPU 有点高"）：
   这里原来是「网格漂移」动画（background-position → 后改 transform），
   实测：动画在跑 → CPU 76ms/2s + 121 次样式重算；停掉 → 25ms + 5 次（省 3 倍 ✗✗）。
   而它只是个**很淡的背景网格**，几乎看不出来 ✓ → 直接改成【静态网格】✓
   （想要"活起来"的观感，宁可只在大屏桌面开，也不要让它每帧吃 CPU ✓）*/
.bg::before {
  content: ""; inset: 0;
  background-image:
    linear-gradient(rgba(34,211,238,.055) 1px, transparent 1px),
    linear-gradient(90deg, rgba(34,211,238,.055) 1px, transparent 1px);
  background-size: 56px 56px;
}
.bg::after {
  content: ""; background:
    radial-gradient(900px 500px at 12% 8%, rgba(34,211,238,.16), transparent 60%),
    radial-gradient(760px 480px at 88% 92%, rgba(168,85,247,.16), transparent 62%),
    radial-gradient(600px 400px at 70% 20%, rgba(163,230,53,.08), transparent 60%);
}

/* ---------------- HUD ---------------- */
.hud {
  position: fixed; top: 0; left: 0; right: 0; height: 58px; z-index: 30;
  display: flex; align-items: center; gap: 14px; padding: 0 18px;
  background: linear-gradient(180deg, rgba(6,10,18,.94), rgba(6,10,18,.55));
  border-bottom: 1px solid var(--line);
}
.hud .node {
  font-family: var(--mono); font-size: 13px; letter-spacing: .12em; color: var(--cyan);
  border: 1px solid rgba(34,211,238,.35); border-radius: 6px; padding: 3px 9px;
  background: rgba(34,211,238,.07); white-space: nowrap;
}
.hud .ttl { font-weight: 700; font-size: 16px; white-space: nowrap; overflow: hidden;
  text-overflow: ellipsis; min-width: 0; max-width: 42ch; }   /* 单行 + 省略号：长标签不再绕行压住进度点 */
.hud .ttl small { color: var(--dim); font-weight: 400; margin-left: 8px; font-family: var(--mono); }
.rail { display: flex; gap: 7px; margin: 0 auto; }
.rail i {
  width: 9px; height: 9px; border-radius: 50%; background: #22314A;
  border: 1px solid #2C3E58; transition: .3s; display: block;
}
.rail i.done { background: var(--lime); border-color: var(--lime); box-shadow: 0 0 10px rgba(163,230,53,.7); }
.rail i.now { background: var(--cyan); border-color: var(--cyan); transform: scale(1.45); box-shadow: 0 0 14px rgba(34,211,238,.9); }
.hud .right { display: flex; align-items: center; gap: 12px; font-family: var(--mono); font-size: 13px; white-space: nowrap; }
.hud .right .link, .hud .right .full, .hud .right .mini, .hud .right .orig { white-space: nowrap; }
/* 桌面端只显示完整标签（老师跳过 / 编程专区）；手机端在下面的媒体查询里切成短标签（跳过 / 退出） */
.hud .right .mini { display: none; }
.hud .stars { color: var(--amber); white-space: nowrap; }
.link { color: var(--dim); text-decoration: none; cursor: pointer; border-bottom: 1px dashed rgba(140,160,190,.5); }
.link:hover { color: var(--cyan); }
/* 顶栏原题链接 */
.hud .hud-orig { display: inline-flex; align-items: center; gap: 6px; }
.hud .hud-orig .orig { color: var(--cyan); border-bottom-color: rgba(34,211,238,.5); font-weight: 700; }
.hud .hud-orig .orig:hover { color: #fff; text-shadow: 0 0 10px rgba(34,211,238,.8); }
.hud .hud-orig .sep { color: var(--dim2); }

/* ---------------- 屏幕容器 ---------------- */
.stage { position: fixed; inset: 58px 0 78px; }
.screen {
  position: absolute; inset: 0; padding: 26px 34px; overflow: auto;
  opacity: 0; transform: translateY(26px) scale(.985); pointer-events: none;
  transition: opacity .45s ease, transform .45s cubic-bezier(.2,.8,.2,1);
}
.screen.on { opacity: 1; transform: none; pointer-events: auto; }
.screen > h2 {
  margin: 0 0 6px; font-size: 27px; display: flex; align-items: center; gap: 12px; flex-wrap: wrap;
}
.screen > h2 .chip {
  font-family: var(--mono); font-size: 12px; letter-spacing: .1em; color: var(--cyan);
  border: 1px solid rgba(34,211,238,.35); background: rgba(34,211,238,.07);
  border-radius: 999px; padding: 3px 11px;
}
.sub { color: var(--dim); margin: 0 0 18px; font-size: 15px; }
.wrap { max-width: 1180px; margin: 0 auto; }
.g2 { display: grid; grid-template-columns: 1.1fr .9fr; gap: 20px; align-items: start; }
/* ★ 2026-10-17：auto-fit —— 一组里只有 1 张卡就撑满整行（原来 fixed 3 列 → 单卡只占 1/3、右边全空 ✗） */
.g3 { display: grid; grid-template-columns: repeat(auto-fit, minmax(320px, 1fr)); gap: 16px; }
.g4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 14px; }
@media (max-width: 1000px) { .g2, .g3, .g4 { grid-template-columns: 1fr; } }

/* ---------------- 卡片 ---------------- */
.glass {
  background: var(--panel); border: 1px solid var(--line); border-radius: 16px; padding: 16px 18px;
  position: relative; overflow: hidden;
}
.glass::after {
  content: ""; position: absolute; inset: 0; pointer-events: none;
  background: linear-gradient(115deg, transparent 40%, rgba(255,255,255,.06) 50%, transparent 60%);
  transform: translateX(-100%);
}
.glass.sweep::after { animation: sweep .9s ease; }
@keyframes sweep { to { transform: translateX(100%); } }
.glass h4 { margin: 0 0 8px; font-size: 16px; display: flex; align-items: center; gap: 8px; }
.glass h4 .tag {
  font-family: var(--mono); font-size: 11px; color: var(--dim); border: 1px solid var(--line);
  border-radius: 5px; padding: 1px 6px;
}
.glass.cy { border-color: rgba(34,211,238,.36); box-shadow: 0 0 0 1px rgba(34,211,238,.08) inset, 0 8px 30px rgba(34,211,238,.09); }
.glass.vi { border-color: rgba(168,85,247,.36); }
.glass.li { border-color: rgba(163,230,53,.34); }
.glass.am { border-color: rgba(251,191,36,.36); }
.glass.pk { border-color: rgba(244,114,182,.34); }
.glass.rd { border-color: rgba(248,113,113,.4); background: rgba(248,113,113,.06); }
.mono { font-family: var(--mono); }
.dim { color: var(--dim); }
.hl-cy { color: var(--cyan); } .hl-li { color: var(--lime); } .hl-am { color: var(--amber); }
.hl-vi { color: var(--violet); } .hl-rd { color: var(--red); }
ul.tick { margin: 6px 0 0 18px; padding: 0; }
ul.tick li { margin: 4px 0; }
ul.tick li::marker { color: var(--cyan); }

/* 逐条出现 */
.reveal { opacity: 0; transform: translateY(14px); transition: .5s cubic-bezier(.2,.8,.2,1); }
.reveal.in { opacity: 1; transform: none; }

/* ---------------- 按钮 ---------------- */
.btn {
  border: 1px solid rgba(34,211,238,.5); background: rgba(34,211,238,.12); color: var(--txt);
  border-radius: 10px; padding: 9px 20px; font-size: 15px; font-weight: 700; cursor: pointer;
  font-family: inherit; transition: .2s; letter-spacing: .02em;
}
.btn:hover { background: rgba(34,211,238,.22); box-shadow: var(--glow); transform: translateY(-1px); }
.btn.primary { background: linear-gradient(135deg, rgba(34,211,238,.9), rgba(59,130,246,.85)); border-color: transparent; color: #04121A; }
.btn.primary:hover { filter: brightness(1.08); }
.btn.li { border-color: rgba(163,230,53,.5); background: rgba(163,230,53,.14); }
.btn.am { border-color: rgba(251,191,36,.5); background: rgba(251,191,36,.14); }
.btn.vi { border-color: rgba(168,85,247,.5); background: rgba(168,85,247,.14); }
.btn.ans-ghost { border-color: var(--line); background: transparent; color: var(--dim); }
.btn:disabled { opacity: .4; cursor: not-allowed; filter: grayscale(.6); }
.btn-row { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; margin-top: 14px; }

/* ---------------- 底部导航 ---------------- */
.nav {
  position: fixed; left: 0; right: 0; bottom: 0; height: 78px; z-index: 30;
  display: flex; align-items: center; gap: 14px; padding: 0 22px;
  background: linear-gradient(0deg, rgba(6,10,18,.96), rgba(6,10,18,.5));
  border-top: 1px solid var(--line);
}
.nav .status { font-family: var(--mono); font-size: 13px; color: var(--dim); flex: 1; }
.nav .status b { color: var(--amber); }
.nav .gate-hint { color: var(--dim2); }
.nav .bar { position: absolute; top: -1px; left: 0; height: 2px; background: linear-gradient(90deg, var(--cyan), var(--lime)); width: 0; transition: width .45s; box-shadow: 0 0 12px rgba(34,211,238,.8); }
.lock { display: inline-flex; align-items: center; gap: 6px; }
.lock.unlocked { color: var(--lime); }

/* ---------------- 代码 ---------------- */
.code {
  background: #060A14; border: 1px solid rgba(120,200,255,.15); border-radius: 14px;
  padding: 14px 16px; font-family: var(--mono); font-size: 14px; line-height: 1.7;
  overflow: auto; max-height: 56vh;
}
.code .row { display: flex; gap: 14px; border-radius: 6px; padding: 0 6px; white-space: pre; opacity: .35; transition: .3s; }
.code .row.on { opacity: 1; background: rgba(34,211,238,.10); box-shadow: inset 3px 0 0 var(--cyan); }
.code .row .n { color: #46587A; width: 26px; text-align: right; flex: none; }
.code .row.hl { opacity: 1; background: rgba(251,191,36,.12); box-shadow: inset 3px 0 0 var(--amber); }
.vars { display: flex; flex-wrap: wrap; gap: 8px; }
.var {
  font-family: var(--mono); font-size: 13px; border: 1px solid rgba(34,211,238,.35);
  background: rgba(34,211,238,.08); border-radius: 9px; padding: 5px 11px;
}
.var b { color: var(--lime); }

/* ---------------- 表格 ---------------- */
table.tbl { width: 100%; border-collapse: separate; border-spacing: 0 7px; }
table.tbl th {
  font-family: var(--mono); font-size: 12.5px; letter-spacing: .08em; color: var(--cyan);
  text-align: left; padding: 6px 12px; border-bottom: 1px solid var(--line);
}
table.tbl td { background: rgba(255,255,255,.035); padding: 9px 12px; font-size: 15px; }
table.tbl tr td:first-child { border-radius: 9px 0 0 9px; color: var(--amber); font-weight: 700; }
table.tbl tr td:last-child { border-radius: 0 9px 9px 0; }
table.tbl tr.hide { display: none; }

/* ---------------- 挑战 / 答题 ---------------- */
.q { margin-bottom: 14px; }
.q h4 { margin: 0 0 6px; font-size: 16.5px; }
.ans { margin-top: 10px; display: none; }
.ans.show { display: block; animation: fadeUp .4s; }
@keyframes fadeUp { from { opacity: 0; transform: translateY(10px); } }
.ok-mark { color: var(--lime); font-weight: 700; }
.q.done { border-color: rgba(163,230,53,.45); }

/* ---------------- 勋章 ---------------- */
.medal { text-align: center; padding: 16px; border-radius: 14px; background: var(--panel); border: 1px solid var(--line); filter: grayscale(1); opacity: .45; transition: .4s; }
.medal.on { filter: none; opacity: 1; border-color: rgba(251,191,36,.5); box-shadow: 0 0 22px rgba(251,191,36,.25); }
.medal .m { font-size: 40px; }

/* ---------------- 首页卡片 ---------------- */
.lesson {
  display: block; text-decoration: none; color: inherit;
  background: var(--panel); border: 1px solid var(--line); border-radius: 16px; padding: 16px;
  transition: .25s; position: relative; overflow: hidden;
}
.lesson:hover { transform: translateY(-5px); border-color: rgba(34,211,238,.5); box-shadow: 0 12px 34px rgba(34,211,238,.14); }
.lesson h3 { margin: 0 0 4px; font-size: 18px; }
.lesson-main { display: block; text-decoration: none; color: inherit; }
.lesson .links { margin-top: 9px; font-size: 12.5px; color: var(--dim2); }
.lesson .links .link { color: var(--dim); border-bottom-color: rgba(140,160,190,.45); }
.lesson .links .link:hover { color: var(--cyan); }
.lesson .tag { font-family: var(--mono); font-size: 12px; color: var(--dim); }
.lesson .pbar { height: 5px; background: #16223A; border-radius: 99px; margin-top: 10px; overflow: hidden; }
.lesson .pbar i { display: block; height: 100%; background: linear-gradient(90deg, var(--cyan), var(--lime)); width: 0; }

/* ---------------- 提示 / 弹出 ---------------- */
.toast {
  position: fixed; left: 50%; bottom: 100px; transform: translate(-50%, 26px); z-index: 60;
  background: rgba(10,16,32,.95); border: 1px solid rgba(163,230,53,.5); color: var(--lime);
  padding: 10px 22px; border-radius: 99px; font-weight: 700; font-family: var(--mono); font-size: 14px;
  opacity: 0; transition: .35s; pointer-events: none; box-shadow: 0 0 26px rgba(163,230,53,.25);
}
.toast.show { opacity: 1; transform: translate(-50%, 0); }
.unlock-flash {
  position: fixed; inset: 0; z-index: 55; pointer-events: none; opacity: 0;
  background: radial-gradient(circle at 50% 60%, rgba(163,230,53,.22), transparent 60%);
}
.unlock-flash.go { animation: flash .7s ease; }
@keyframes flash { 0% { opacity: 0 } 30% { opacity: 1 } 100% { opacity: 0 } }
/* ---------------- 品牌 logo（深色主题下加白色圆角底） ---------------- */
.logo {
  height: 30px; width: auto; display: block; border-radius: 6px; background: #fff;
  padding: 2px 4px; box-shadow: 0 0 0 1px rgba(255,255,255,.25), 0 2px 10px rgba(0,0,0,.35);
}
.brand { display: flex; align-items: center; gap: 9px; font-weight: 700; white-space: nowrap; }
/* 首屏副标题：互动课堂 */
.hero-sub {
  margin: 2px 0 0; font-size: 21px; font-weight: 700; letter-spacing: .34em;
  color: var(--cyan); text-shadow: 0 0 18px rgba(34,211,238,.45);
}
.hero-sub::before { content: ""; display: inline-block; width: 30px; height: 2px; vertical-align: middle;
  background: linear-gradient(90deg, var(--cyan), transparent); margin-right: 12px; }
.logo-hero {
  width: 134px; height: auto; border-radius: 12px; background: #fff; padding: 6px 8px;
  box-shadow: 0 0 0 1px rgba(255,255,255,.22), 0 6px 22px rgba(0,0,0,.4); flex: none;
}
@media (max-width: 820px) {
  .logo { height: 24px; padding: 1px 3px; }
  .brand { font-size: 13.5px; gap: 6px; }
  .logo-hero { width: 104px; }
}

/* ---------------- 编程闯关 ---------------- */
.quest-goal {
  border: 1px solid rgba(251,191,36,.4); background: rgba(251,191,36,.07);
  border-radius: 12px; padding: 10px 14px; margin: 4px 0 14px; font-size: 15.5px;
}
.quest-body { margin-bottom: 12px; }
.opt {
  border: 1px solid var(--line); background: rgba(255,255,255,.035); border-radius: 12px;
  padding: 10px 13px; margin-bottom: 9px; cursor: pointer; transition: .18s; display: flex; gap: 10px;
}
.opt:hover { border-color: rgba(34,211,238,.5); background: rgba(34,211,238,.07); }
.opt.sel { border-color: var(--cyan); background: rgba(34,211,238,.13); box-shadow: var(--glow); }
.opt.wrong { border-color: var(--red); background: rgba(248,113,113,.12); animation: shake .35s; }
.opt pre { margin: 0; font-family: var(--mono); font-size: 14px; white-space: pre-wrap; word-break: break-all; }
@keyframes shake { 25% { transform: translateX(-6px) } 75% { transform: translateX(6px) } }
.code-fill { background: #060A14; border: 1px solid rgba(120,200,255,.15); border-radius: 14px; padding: 12px 14px; }
.fline { font-family: var(--mono); font-size: 14px; line-height: 2.1; white-space: pre-wrap; word-break: break-all; }
.fline > span { white-space: pre-wrap; }
input.blank {
  font-family: var(--mono); font-size: 14px; color: var(--lime); background: rgba(163,230,53,.09);
  border: 1px dashed rgba(163,230,53,.55); border-radius: 7px; padding: 2px 7px; outline: none;
}
input.blank:focus { border-style: solid; box-shadow: 0 0 12px rgba(163,230,53,.35); }
input.blank.bad { border-color: var(--red); background: rgba(248,113,113,.12); color: #FFD7D7; }
.ord-pool { display: flex; flex-direction: column; gap: 8px; }
.ord-picked { display: flex; flex-direction: column; gap: 8px; margin-bottom: 12px; min-height: 44px;
  border: 1px dashed rgba(120,200,255,.3); border-radius: 12px; padding: 10px; }
.ord-card {
  border: 1px solid var(--line); background: rgba(255,255,255,.035); border-radius: 10px;
  padding: 9px 12px; cursor: pointer; transition: .18s; font-size: 15px; display: flex; gap: 9px;
}
.ord-card:hover { border-color: rgba(34,211,238,.5); transform: translateX(3px); }
.ord-card.used { opacity: .35; cursor: default; }
.ord-card.picked { background: rgba(163,230,53,.09); border-color: rgba(163,230,53,.5); }
.mini-code { font-family: var(--mono); font-size: 13px; line-height: 1.75; color: #BFE3FF; }
.quest-meta { font-size: 12.5px; color: var(--dim2); }
.hud .xp { color: var(--lime); white-space: nowrap; }

/* ---------------- 知识图谱 ---------------- */
.kgtag {
  display: inline-block; font-size: 12.5px; border: 1px solid var(--line); border-radius: 999px;
  padding: 3px 10px; margin: 0 6px 6px 0; color: var(--dim); background: rgba(255,255,255,.04);
}
.kgtag b { color: var(--amber); margin-left: 5px; font-weight: 700; }
.kgtag.main { border-color: rgba(34,211,238,.5); color: var(--cyan); background: rgba(34,211,238,.08); }
.kgtag.more { opacity: .8; }
.lvl { font-family: var(--mono); font-size: 13px; color: var(--amber); white-space: nowrap; }
.lvl.lv8, .lvl.lv9, .lvl.lv10 { color: var(--red); }
.lvl.lv1, .lvl.lv2, .lvl.lv3 { color: var(--lime); }
.lesson.sel-stage { border-color: var(--cyan); box-shadow: 0 0 0 1px rgba(34,211,238,.35), 0 10px 30px rgba(34,211,238,.16); }
.rowfilter { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; margin-bottom: 12px; }
.rowfilter select {
  background: #0B1220; color: var(--txt); border: 1px solid var(--line); border-radius: 10px;
  padding: 8px 10px; font-family: inherit; font-size: 14px;
}

/* ==================== 手机 / 触屏适配 ==================== */
.confetti { position: fixed; inset: 0; pointer-events: none; z-index: 70; overflow: hidden; }
.confetti i { position: absolute; width: 8px; height: 14px; border-radius: 2px; animation: fall 2.4s linear forwards; }
img { max-width: 100%; height: auto; }
html { -webkit-text-size-adjust: 100%; }
.tw { overflow-x: auto; -webkit-overflow-scrolling: touch; }
.tw > table.tbl { min-width: 460px; }
.btn, .link, .lesson { -webkit-tap-highlight-color: rgba(34,211,238,.18); }
.btn:active { transform: scale(.97); }

/* 中等宽度（小笔记本 / 平板横屏）：顶栏压缩，避免换行 */
@media (max-width: 1250px) {
  .hud { gap: 10px; }
  .hud .ttl small { display: none; }
  .hud .right { gap: 9px; font-size: 12.5px; }
  .rail i { width: 7px; height: 7px; }
  .rail { gap: 5px; }
}

/* 平板 / 小笔记本 */
@media (max-width: 1100px) {
  .screen { padding: 20px 20px; }
  .g2 { grid-template-columns: 1fr; }
}

/* 手机 */
@media (max-width: 820px) {
  body { font-size: 15px; }
  /* 顶栏精简：隐藏圆点进度，只留 NODE 计数 + 星星 */
  .hud { height: 50px; padding: 0 10px; gap: 8px; }
  .hud .node { font-size: 11px; padding: 2px 7px; letter-spacing: .08em; }
  .hud .ttl { font-size: 14px; max-width: 40vw; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
  .hud .ttl small { display: none; }
  .rail { display: none; }
  .hud .right { margin-left: auto; gap: 10px; font-size: 12.5px; }
  /* 手机上顶栏：只留一个原题入口（一本通优先），其余链接图标化/缩写 */
  .hud .right .full { display: none; }
  .hud .right .mini { display: inline; }
  .hud .right .hud-home { display: none; }
  .hud .right #snd .lbl { display: none; }
  .hud .right { gap: 9px; }
  .hud .hud-orig .orig { font-size: 12px; }
  /* 主屏与底部导航：给导航留出两行高度 */
  .stage { inset: 50px 0 112px; }
  .screen { padding: 14px 13px 10px; -webkit-overflow-scrolling: touch; }
  .screen > h2 { font-size: 19px; gap: 8px; line-height: 1.35; display: block; }
  .screen > h2 .chip { font-size: 10.5px; padding: 2px 8px; display: inline-block; margin-top: 7px; }
  .idx-hero { flex-direction: column; align-items: flex-start !important; }
  .idx-hero img { width: 84px; }
  .hud-hint { display: none; }
  .wrap { padding-left: 14px !important; padding-right: 14px !important; }
  .screen canvas { max-width: 100% !important; height: auto !important; }
  .sub { font-size: 13.5px; margin-bottom: 12px; }
  .g2, .g3, .g4 { grid-template-columns: 1fr; gap: 10px; }
  .glass { padding: 12px 13px; border-radius: 13px; }
  .glass h4 { font-size: 15px; gap: 6px; flex-wrap: wrap; }
  .btn-row { gap: 8px; margin-top: 10px; }
  .btn { min-height: 44px; padding: 10px 16px; font-size: 15px; }
  /* 底部导航：状态一行 + 两个大按钮 */
  .nav { height: 112px; padding: 8px 10px calc(8px + env(safe-area-inset-bottom)); flex-wrap: wrap; gap: 8px; }
  .nav .status { flex: 1 1 100%; order: -1; font-size: 12.5px; line-height: 1.4; }
  .nav .gate-hint { display: none; }
  .nav #prev { flex: 0 0 34%; }
  .nav #next { flex: 1 1 auto; }
  /* 代码：更小字号 + 横向滚动 */
  .code { font-size: 12px; line-height: 1.62; padding: 10px 10px; max-height: 46vh; border-radius: 12px; }
  .code .row { gap: 8px; padding: 0 4px; }
  .code .row .n { width: 20px; }
  .var { font-size: 12px; padding: 4px 9px; }
  .vars { gap: 6px; }
  /* 表格：可横向滑动，字号收小 */
  table.tbl th { font-size: 11.5px; padding: 5px 9px; }
  table.tbl td { font-size: 13.5px; padding: 7px 9px; }
  .medal .m { font-size: 32px; }
  .toast { bottom: 128px; font-size: 13px; max-width: 88vw; text-align: center; }
  .confetti i { width: 7px; height: 12px; }
}

/* 小屏手机 */
@media (max-width: 420px) {
  .screen > h2 { font-size: 17.5px; }
  .hud .ttl { max-width: 34vw; }
  .hud .right .link { font-size: 12px; }
  .btn { font-size: 14px; padding: 9px 13px; }
  .nav { height: 118px; }
  .screen { padding: 12px 10px 8px; }
  .glass { padding: 11px 12px; }
}

/* 矮屏（横屏手机 / 小笔记本） */
@media (max-height: 620px) {
  .code { max-height: 38vh; }
  .stage { inset: 50px 0 104px; }
}

/* 触屏设备：悬停效果改为按压反馈 */
@media (hover: none) {
  .glass:hover, .lesson:hover { transform: none; }
  .btn:hover { box-shadow: none; }
}

@keyframes fall { 0% { transform: translateY(-30px) rotate(0); opacity: 1 } 100% { transform: translateY(104vh) rotate(680deg); opacity: .85 } }
::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-thumb { background: #1B2942; border-radius: 99px; }
::-webkit-scrollbar-track { background: transparent; }

/* ---------- 每屏反馈 + 排行榜入口：右侧竖排、随页面一起滚动 ----------
   kk老师 2026-10-13：放到右边、可收起展开、新打开课件默认展开。
   kk老师 2026-10-19：反馈按钮和「排行榜」要一起靠着网页右边、竖排，**随着页面一起滑动**（不再钉在屏幕上 ✗） */
.fb-dock { position: fixed; right: 16px; top: 50%; transform: translateY(-50%);
           z-index: 26; display: flex; flex-direction: column; align-items: flex-end; gap: 8px;
           width: fit-content; max-width: calc(100vw - 32px); max-height: calc(100vh - 150px);
           overflow-y: auto; padding: 2px 0; }
@media (min-width: 900px) { .screen { padding-right: 160px; } }
.fb-rank { font: inherit; font-size: 13px; line-height: 1; padding: 9px 14px; cursor: pointer;
           text-decoration: none; display: inline-block; border-radius: 999px;
           color: #FDE68A; background: rgba(251, 191, 36, .14); border: 1px solid rgba(251, 191, 36, .45);
           box-shadow: 0 8px 22px rgba(0, 0, 0, .35); transition: .18s; }
.fb-rank:hover { background: rgba(251, 191, 36, .22); border-color: #FBBF24; transform: translateY(-1px); }
.fb { position: relative; z-index: 5; width: min(300px, calc(100vw - 28px));
      padding: 12px 14px; border-radius: 16px; text-align: left;
      background: rgba(13, 22, 40, .92); border: 1px solid rgba(147, 165, 196, .30);
      box-shadow: 0 18px 46px rgba(0, 0, 0, .5); }
.fb.collapsed { width: auto; padding: 0; border: 0; background: transparent; box-shadow: none; }
.fb-head { display: flex; align-items: center; justify-content: space-between; gap: 8px; margin-bottom: 8px; }
.fb .fb-t { font-size: 12.5px; color: #93A5C4; letter-spacing: .04em; }
.fb-toggle { font: inherit; font-size: 12.5px; padding: 7px 12px; cursor: pointer; border-radius: 999px;
             color: #E6EFFF; background: rgba(27, 39, 64, .9); border: 1px solid rgba(147, 165, 196, .35);
             box-shadow: 0 8px 22px rgba(0, 0, 0, .45); transition: .18s; }
.fb-toggle:hover { border-color: #22D3EE; color: #22D3EE; }
.fb-toggle .fb-mark { display: inline-block; width: 6px; height: 6px; margin-left: 6px; border-radius: 50%;
                      background: #22D3EE; vertical-align: middle; }
.fb-btns { display: flex; flex-wrap: wrap; gap: 8px; }
.fb-btn { font: inherit; font-size: 13px; line-height: 1; padding: 8px 13px; cursor: pointer;
          border-radius: 999px; color: #E6EFFF; background: rgba(27, 39, 64, .72);
          border: 1px solid rgba(147, 165, 196, .30); transition: .18s; }
.fb-btn:hover { background: rgba(42, 74, 124, .85); border-color: rgba(34, 211, 238, .55); transform: translateY(-1px); }
.fb-btn.on { background: rgba(34, 211, 238, .20); border-color: #22D3EE; color: #22D3EE; font-weight: 700; }
.fb-btn.ans-ghost { background: transparent; }
.fb-ok { font-size: 12.5px; color: #22D3EE; margin-top: 7px; min-height: 1px; }
.fb-note { margin-top: 7px; font-size: 12.5px; color: #9FB3D0; background: rgba(27, 39, 64, .6);
           border: 1px solid rgba(147, 165, 196, .22); border-radius: 10px; padding: 5px 9px; }
.fb-form { margin-top: 9px; display: flex; flex-wrap: wrap; gap: 8px; }
.fb-form textarea { flex: 1 1 100%; min-height: 62px; padding: 9px 11px; font: inherit; font-size: 13.5px;
                    color: #E6EFFF; background: rgba(27, 39, 64, .78); border-radius: 12px;
                    border: 1px solid rgba(147, 165, 196, .35); resize: vertical; }
.fb-form textarea:focus { outline: none; border-color: #22D3EE; box-shadow: 0 0 0 3px rgba(34, 211, 238, .16); }
.fb-send, .fb-cancel { font: inherit; font-size: 13px; padding: 8px 14px; border-radius: 10px; cursor: pointer;
                       border: 1px solid rgba(34, 211, 238, .55); color: #06121A; font-weight: 700;
                       background: linear-gradient(135deg, #22D3EE, #3B82F6); }
.fb-cancel { background: transparent; color: #9FB3D0; border-color: rgba(147, 165, 196, .35); font-weight: 400; }

/* ---------- 互动按钮尽量靠右（右手鼠标习惯）---------- */
.btn-row { justify-content: flex-end; }
.rail i { cursor: pointer; }
.rail i.jump:hover { border-color: #22D3EE; transform: scale(1.35); box-shadow: 0 0 12px rgba(34, 211, 238, .7); }
.rail i.now.jump:hover { transform: scale(1.55); }

@media (max-width: 680px) {
  .fb { width: min(260px, calc(100vw - 16px)); padding: 10px 12px; }
  .fb-dock { top: auto; bottom: 88px; right: 8px; transform: none; gap: 7px; max-height: 58vh; }
  .fb-btn { padding: 8px 11px; }
  .btn-row { justify-content: flex-end; }   /* 手机上同样靠右，避免误触 */
}

/* 窄屏隐藏 HUD 课题（窄屏优先保证进度点与星星可点）*/
@media (max-width: 820px) { .hud .ttl { display: none; } }

/* ---------- 身份徽标：老师预览 / 家长查看（学生不显示）---------- */
.hud .role-badge { font-size: 12px; white-space: nowrap; padding: 4px 10px; border-radius: 999px; margin-right: 4px; }
.hud .role-badge.teacher { color: #FBBF24; border: 1px solid rgba(251,191,36,.45); background: rgba(251,191,36,.12); }
.hud .role-badge.parent  { color: #A3E635; border: 1px solid rgba(163,230,53,.45); background: rgba(163,230,53,.12); }
@media (max-width: 820px) { .hud .role-badge { font-size: 11px; padding: 3px 8px; } }

/* ---------- 通关屏「专项训练」弹出练习窗口（kk老师 2026-10-13）---------- */
.practice-card h4 { margin: 0 0 2px; }
.pm { position: fixed; inset: 0; z-index: 200; display: none; align-items: center; justify-content: center;
      background: rgba(3, 7, 14, .93); padding: 18px; }
.pm.on { display: flex; }
.pm-box { width: min(1100px, 100%); height: min(88vh, 100%); display: flex; flex-direction: column;
          background: #0A1324; border: 1px solid rgba(34, 211, 238, .35); border-radius: 18px; overflow: hidden;
          box-shadow: 0 30px 80px rgba(0, 0, 0, .7); }
.pm-head { display: flex; align-items: center; gap: 12px; padding: 12px 16px; color: #E6EFFF;
           background: linear-gradient(135deg, rgba(34, 211, 238, .16), rgba(59, 130, 246, .12));
           border-bottom: 1px solid rgba(147, 165, 196, .25); }
.pm-head .pm-tip { flex: 1; font-size: 12.5px; color: #93A5C4; }
.pm-close { font: inherit; font-size: 13px; padding: 7px 14px; border-radius: 999px; cursor: pointer;
            color: #E6EFFF; background: rgba(27, 39, 64, .9); border: 1px solid rgba(147, 165, 196, .4); }
.pm-close:hover { border-color: #22D3EE; color: #22D3EE; }
.pm-frame { flex: 1; width: 100%; border: 0; background: #060A12; }
@media (max-width: 560px) { .pm { padding: 8px; } .pm-head { padding: 10px 12px; } .pm-tip { display: none; } }

/* ============================================================================
   第 8 课《循环控制语句》新增互动组件（kk老师 2026-10-15 优化要点）
   ① 老师提问 · 举手抢答   ② 快问快答（选择 + 打字）   ③ 互动实验室   ④ 整课反馈弹窗
   ========================================================================== */

/* ---------- 通用按钮补充 ---------- */
.btn.rd   { background: linear-gradient(135deg,#FB7185,#E11D48); color: #fff; border-color: rgba(251,113,133,.6); }
.btn.big  { font-size: 17px; padding: 13px 26px; }
.btn:disabled { opacity: .45; cursor: not-allowed; }

/* ---------- ① 老师提问 · 举手抢答 ---------- */
.ask-box { display: flex; gap: 16px; align-items: flex-start; margin: 6px 0 14px; }
.ask-avatar { font-size: 46px; line-height: 1; cursor: pointer; user-select: none; flex: 0 0 auto;
              filter: drop-shadow(0 0 12px rgba(34,211,238,.35)); transition: transform .18s; }
.ask-avatar.wave { animation: askWave .45s ease-in-out 2; }
@keyframes askWave { 0%,100% { transform: rotate(0) } 25% { transform: rotate(-12deg) } 75% { transform: rotate(12deg) } }
.ask-bubble { position: relative; flex: 1; padding: 16px 20px; border-radius: 16px;
              background: linear-gradient(135deg, rgba(34,211,238,.14), rgba(168,85,247,.10));
              border: 1px solid rgba(34,211,238,.35); }
.ask-bubble::before { content: ""; position: absolute; left: -8px; top: 22px; width: 14px; height: 14px;
                      background: inherit; border-left: 1px solid rgba(34,211,238,.35);
                      border-bottom: 1px solid rgba(34,211,238,.35); transform: rotate(45deg); }
.ask-who { font-size: 12px; letter-spacing: .12em; color: var(--cyan); margin-bottom: 6px; }
.ask-q { font-size: 21px; font-weight: 700; line-height: 1.55; }
.ask-tip { margin-top: 10px; font-size: 14px; color: var(--dim); border-top: 1px dashed var(--line); padding-top: 8px; }
.ask-kids { display: flex; flex-wrap: wrap; gap: 8px; min-height: 30px; margin-bottom: 6px; }
.ask-kids .kid { padding: 6px 14px; border-radius: 999px; font-size: 14px; color: #04121a; font-weight: 700;
                 background: linear-gradient(135deg,#FBBF24,#F59E0B); animation: kidIn .35s backwards; }
@keyframes kidIn { from { opacity: 0; transform: translateY(8px) scale(.9) } to { opacity: 1 } }

/* ---------- ② 快问快答（选择 + 打字输入代码） ---------- */
.drill-head { display: flex; gap: 16px; justify-content: space-between; font-size: 13px; color: var(--dim);
              margin-bottom: 10px; padding: 8px 14px; border-radius: 10px; background: var(--panel);
              border: 1px solid var(--line); }
.drill-item { margin-bottom: 14px; }
.drill-item.done { border-color: rgba(163,230,53,.5); }
.drill-item h4 { font-size: 16px; display: block; }
.drill-opts { display: flex; flex-wrap: wrap; gap: 8px; margin: 10px 0 4px; }
.drill-opt { font: inherit; font-size: 14px; padding: 9px 14px; border-radius: 10px; cursor: pointer;
             color: var(--txt); background: rgba(20,30,52,.85); border: 1px solid rgba(147,165,196,.35);
             transition: all .15s; text-align: left; }
.drill-opt:hover { border-color: var(--cyan); color: var(--cyan); }
.drill-opt.on { background: rgba(163,230,53,.22); border-color: var(--lime); color: #EAFBD0; }
.drill-opt.bad { background: rgba(248,113,113,.22); border-color: var(--red); animation: shake .3s; }
@keyframes shake { 0%,100% { transform: translateX(0) } 25% { transform: translateX(-5px) } 75% { transform: translateX(5px) } }
.drill-type { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; margin: 8px 0 2px; }
.drill-input { flex: 1 1 220px; min-width: 180px; font-family: var(--mono); font-size: 15px; padding: 10px 14px;
               border-radius: 10px; color: #EAF6FF; background: rgba(6,12,24,.95);
               border: 1px solid rgba(147,165,196,.4); caret-color: var(--cyan); }
.drill-input:focus { outline: none; border-color: var(--cyan); box-shadow: 0 0 0 3px rgba(34,211,238,.16); }
.drill-input.ok { border-color: var(--lime); background: rgba(163,230,53,.10); }
.drill-input.bad { border-color: var(--red); background: rgba(248,113,113,.10); animation: shake .3s; }
.drill-fb { margin-top: 8px; }
.drill-fb:empty { display: none; }

/* ---------- ③ 互动实验室 ---------- */
.lab-goal { margin: 8px 0 12px; padding: 10px 16px; border-radius: 12px; font-size: 15px;
            background: rgba(251,191,36,.10); border: 1px solid rgba(251,191,36,.35); color: #FDE9B8; }
.lab-wrap { display: grid; grid-template-columns: minmax(0,1.55fr) minmax(220px,1fr); gap: 14px; align-items: stretch; }
.lab-cv { width: 100%; height: 320px; display: block; border-radius: 14px;
          border: 1px solid rgba(34,211,238,.28); background: #060C18; }
.lab-side { display: flex; flex-direction: column; gap: 10px; }
.lab-stat { display: flex; flex-direction: column; gap: 6px; padding: 12px 14px; border-radius: 12px;
            background: var(--panel); border: 1px solid var(--line); }
.lab-kv { display: flex; justify-content: space-between; gap: 10px; font-size: 14px; }
.lab-kv span { color: var(--dim); }
.lab-kv b { font-family: var(--mono); }
.lab-ctrl { padding: 12px 14px; border-radius: 12px; background: var(--panel); border: 1px solid var(--line); }
.lab-row { display: flex; align-items: center; gap: 8px; font-size: 14px; color: var(--dim); margin-bottom: 6px; }
.lab-row input[type=range] { flex: 1; accent-color: var(--cyan); }
.lab-row input[type=number] { font-family: var(--mono); font-size: 14px; padding: 5px 8px; border-radius: 8px;
                              color: #EAF6FF; background: rgba(6,12,24,.95); border: 1px solid rgba(147,165,196,.4); }
.lab-x { font-family: var(--mono); font-size: 15px; color: var(--cyan); }
.lab-legend { display: flex; flex-direction: column; gap: 6px; padding: 10px 14px; border-radius: 12px;
              background: var(--panel); border: 1px solid var(--line); font-size: 13px; color: var(--dim); }
.lab-lg { display: flex; align-items: center; gap: 8px; }
.lab-lg i { width: 12px; height: 12px; border-radius: 3px; display: inline-block; flex: 0 0 auto; }

/* ---------- ④ 整课反馈弹窗 ---------- */
.fbmask { position: fixed; inset: 0; z-index: 300; display: flex; align-items: center; justify-content: center;
          padding: 18px; background: rgba(3,7,14,.93); animation: fbIn .25s ease; }
@keyframes fbIn { from { opacity: 0 } to { opacity: 1 } }
.fbdialog { width: min(620px,100%); max-height: 92vh; overflow: auto; padding: 24px 26px; border-radius: 20px;
            background: linear-gradient(160deg,#0B1426,#0A1020); border: 1px solid rgba(34,211,238,.4);
            box-shadow: 0 30px 90px rgba(0,0,0,.72), 0 0 60px rgba(34,211,238,.12); }
.fbdt { display: flex; align-items: center; gap: 10px; font-size: 22px; font-weight: 800; margin-bottom: 6px; }
.fbdsub { margin: 0 0 16px; color: var(--dim); font-size: 14px; }
.fbbig { display: flex; gap: 14px; margin-bottom: 14px; }
.fbbtn { flex: 1; font: inherit; font-size: 15px; padding: 16px 10px; border-radius: 14px; cursor: pointer;
         color: var(--txt); background: rgba(20,30,52,.85); border: 1px solid rgba(147,165,196,.35);
         display: flex; flex-direction: column; align-items: center; gap: 6px; transition: all .15s; }
.fbbtn span { font-size: 14px; }
.fbbtn:hover { border-color: var(--cyan); }
.fbbtn.on { background: rgba(34,211,238,.20); border-color: var(--cyan); box-shadow: 0 0 22px rgba(34,211,238,.25); }
.fbtext { width: 100%; min-height: 82px; resize: vertical; font: inherit; font-size: 14px; padding: 12px 14px;
          border-radius: 12px; color: #EAF6FF; background: rgba(6,12,24,.95);
          border: 1px solid rgba(147,165,196,.4); caret-color: var(--cyan); }
.fbtext:focus { outline: none; border-color: var(--cyan); }
.fbquick { display: flex; flex-wrap: wrap; gap: 8px; margin: 10px 0 14px; }
.fbq { font: inherit; font-size: 12.5px; padding: 6px 12px; border-radius: 999px; cursor: pointer;
       color: var(--dim); background: rgba(20,30,52,.8); border: 1px solid rgba(147,165,196,.3); }
.fbq:hover { color: var(--cyan); border-color: var(--cyan); }
.fbq.on { color: #04121a; background: var(--cyan); border-color: var(--cyan); font-weight: 700; }

/* ---------- 响应式（手机 390×844 真机视口） ---------- */
@media (max-width: 880px) {
  .lab-wrap { grid-template-columns: 1fr; }
  .lab-cv { height: 260px; }
  .ask-q { font-size: 18px; }
  .ask-avatar { font-size: 38px; }
}
@media (max-width: 560px) {
  .drill-head { flex-direction: column; gap: 4px; }
  .lab-cv { height: 300px; }
  .fbdialog { padding: 18px 16px; border-radius: 16px; }
  .fbdt { font-size: 18px; }
  .fbbig { gap: 10px; }
  .fbbtn { padding: 13px 8px; font-size: 14px; }
  .ask-box { gap: 10px; }
  .ask-bubble { padding: 12px 14px; }
  .drill-opt { font-size: 13px; padding: 8px 11px; }
}
/* ---------- kk 老师独创「三步读题法」（读题屏的折叠提示 · kk老师 2026-10-15） ----------
   定位：只是读题提醒，不是知识点、不参与解锁；收起时只占一个按钮 ✓ */
.rtip { margin: 0 0 12px; }
.rtip-btn { display: flex; align-items: center; gap: 10px; width: 100%; text-align: left;
            font: inherit; font-size: 14px; padding: 10px 16px; border-radius: 12px; cursor: pointer;
            color: #FDE9B8; background: rgba(251,191,36,.10); border: 1px dashed rgba(251,191,36,.5);
            transition: all .15s; }
.rtip-btn:hover { border-style: solid; border-color: var(--amber); color: var(--amber); }
.rtip-x { margin-left: auto; font-size: 12.5px; color: var(--dim); white-space: nowrap; }
.rtip-box { margin-top: 10px; padding: 14px 18px; border-radius: 14px;
            background: linear-gradient(160deg, rgba(251,191,36,.08), rgba(34,211,238,.05));
            border: 1px solid rgba(251,191,36,.35); }
.rtip-h { font-size: 15px; margin-bottom: 8px; }
.rtip-row { display: flex; gap: 12px; align-items: flex-start; padding: 9px 0;
            border-top: 1px dashed rgba(148,163,184,.2); }
.rtip-row:first-of-type { border-top: 0; }
.rtip-k { flex: 0 0 34px; height: 34px; border-radius: 10px; display: inline-flex;
          align-items: center; justify-content: center; font-size: 17px; font-weight: 700;
          color: #04121A; background: linear-gradient(135deg, #FBBF24, #F59E0B); }
.rtip-t { font-size: 14.5px; line-height: 1.65; }
.rtip-i { font-size: 11.5px; color: var(--dim); margin-right: 8px; }
.rtip-f { margin-top: 10px; padding-top: 8px; font-size: 12.5px; color: var(--dim);
          border-top: 1px dashed rgba(148,163,184,.2); }
@media (max-width: 560px) {
  .rtip-btn { font-size: 13px; padding: 9px 12px; }
  .rtip-x { display: none; }
  .rtip-t { font-size: 13.5px; }
  .rtip-box { padding: 12px 14px; }
}

/* ---------- 视频屏（R.video · Manim 讲解动画）kk老师 2026-10-15 ---------- */
.vdo-box { padding: 10px; }
.vdo { width: 100%; display: block; border-radius: 12px; background: #05070D; aspect-ratio: 16 / 9; cursor: pointer; }
.vdo-bar { display: flex; align-items: center; gap: 10px; margin-top: 8px; flex-wrap: wrap; }
.vdo-meta { font-size: 12.5px; opacity: .72; }
.btn.sm { padding: 6px 12px; font-size: 13px; }
/* 全屏态：视频铺满，黑底 */
.vdo-box:fullscreen { padding: 0; background: #000; display: flex; align-items: center; justify-content: center; }
.vdo-box:fullscreen .vdo { width: 100%; height: 100%; aspect-ratio: auto; border-radius: 0; }
.vdo-box:-webkit-full-screen { padding: 0; background: #000; }
.vdo-box:-webkit-full-screen .vdo { width: 100%; height: 100%; border-radius: 0; }
@media (max-width: 520px) {
  .vdo-box { padding: 6px; }
  .vdo { border-radius: 10px; }
  .vdo-bar { gap: 8px; }
}

/* ★ 练习卡片的按钮别顶到右下角（kk老师 2026-10-15：第 20 课的「打开练习」被反馈浮层挡住 ✗）
   「每屏反馈」是固定浮层（right:18px / bottom:96px），按钮靠右就会钻到它下面 ✗
   → 右侧留出浮层的宽度，按钮左移一点，仍然靠右但不重叠 ✓ */
.practice-card .btn-row { padding-right: 148px; }
@media (max-width: 680px) {
  .practice-card .btn-row { padding-right: 132px; }
}

/* ---------------- 站内统一页脚（kk老师 2026-10-15） ----------------
   与平台页面 .p-foot 完全同款：居中 · 13px · 灰色 · 上边一条细线 ✓
   （课件站自己的页面：编程专区 / 平台首页 mock ✓） */
.site-foot {
  margin-top: 30px; padding: 16px 20px; text-align: center; font-size: 13px;
  color: var(--dim2); border-top: 1px solid var(--line);
}
.site-foot a { color: var(--cyan); text-decoration: none; }
.site-foot a:hover { color: #fff; }
.ft-qr-mask {
  display: none; position: fixed; inset: 0; background: rgba(0, 0, 0, .72); z-index: 9999;
  align-items: center; justify-content: center;
}
.ft-qr-box {
  background: #0f1622; border: 1px solid rgba(255, 255, 255, .18); border-radius: 16px;
  padding: 18px; text-align: center; color: #dfe9ff; font-size: 14px;
}
.ft-qr-box img { width: 240px; height: 240px; display: block; border-radius: 8px; margin: 10px 0; }

/* ★ 内容区按钮排别顶到右下角（kk老师 2026-10-16 · 第 9 课互动实验室发现）：
   「每屏反馈」浮层固定在 right:18px / bottom:96px ✗ —— 内容里靠右的按钮
   （如「✔ 我玩明白了」「✔ 我读懂了」）会被它压住一半，点起来很难 ✗。
   → 统一给内容区按钮排留出浮层宽度：仍然靠右 ✓ 但不会被盖住 ✓
   （底部导航「上一屏 / 下一屏」在 .wrap 之外，不受影响 ✓） */
.wrap .btn-row { padding-right: 240px; }
/* 底部也留出浮层高度：这样内容区最后一行按钮完全不会和浮层重叠 ✓（只是页面下方多一点空白 ✓） */
.wrap { padding-bottom: 150px; }
@media (max-width: 680px) {
  .wrap .btn-row { padding-right: 192px; }
  .wrap { padding-bottom: 118px; }
}

/* ---------- 打字练习的「半透明幽灵答案」（kk老师 2026-10-16 定）----------
   输入框里直接淡显正确答案：敲对的部分变实 ✓、敲错的字母标红 ✓ 后面接应敲的字 ✓、
   整句敲对后全句真实显示 ✓ —— 就是「照着敲一遍」的手感 ✓ */
.ans-wrap { position: relative; flex: 1 1 220px; min-width: 180px; display: block; }
.ans-wrap .ans-in { width: 100%; color: transparent; }
.ans-wrap .ans-in.shown { color: #EAF6FF; }          /* 判对后显示真实文字 ✓ */
.ans-ghost {
  position: absolute; left: 1px; right: 1px; top: 1px; bottom: 1px;
  display: flex; align-items: center; padding: 10px 14px;
  font-family: var(--mono); font-size: 15px; white-space: pre; overflow: hidden;
  pointer-events: none; border-radius: 9px;
}
.ans-ghost .g-ok { color: #EAF6FF; }                          /* 敲对的部分：实 ✓ */
.ans-ghost .g-rest { color: rgba(140, 160, 190, .42); }       /* 还没敲的：半透明 ✓ */
.ans-ghost .g-bad { color: #FB7185; background: rgba(251, 113, 133, .20); border-radius: 3px; }
.ans-ok .ans-ghost .g-rest { color: #EAF6FF; }              /* 整句对了：全实 ✓ */
@media (max-width: 680px) { .ans-ghost { font-size: 14px; padding: 9px 12px; } }

/* 单组单卡时不宜拉太宽（观感 ✓） */
.g3 > .lesson { max-width: 720px; }