/* ===== ZBLL 练习 ===== */
/* 所有颜色都走变量，暗色主题只覆盖变量值。新增样式时别写死颜色。 */
:root {
  color-scheme: light;
  --bg: #f2f4f8;
  --card: #ffffff;
  --card2: #f0f2f7;        /* 悬停底 / 药丸底 */
  --card3: #fafbff;        /* 更淡的悬停底 */
  --ink: #1a1d24;
  --dim: #7a8296;
  --line: #e2e6ee;
  --line-strong: #c9d2e6;
  --hover-line: #b9c8ee;
  --accent: #2f6bff;
  --accent-hover: #2659d8;
  --accent-soft: #e8efff;
  --on-accent: #ffffff;
  --kbd-ink: #48506a;
  --kbd-bg: #f0f2f7;
  --kbd-border: #e2e6ee;
  --track: #d3d9e6;        /* 开关滑轨（关） */
  --knob: #ffffff;
  --ok: #10a36a;
  --radius: 14px;
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --bg: #0e1016;
  --card: #171a22;
  --card2: #1f232d;
  --card3: #1c202a;
  --ink: #e7eaf2;
  --dim: #8b93a7;
  --line: #272c38;
  --line-strong: #3a4252;
  --hover-line: #4a5b86;
  --accent: #5b8cff;
  --accent-hover: #7ba3ff;
  --accent-soft: #1a2440;
  --on-accent: #0b0d12;
  --kbd-ink: #c2c9db;
  --kbd-bg: #232833;
  --kbd-border: #333a49;
  --track: #333a49;
  --knob: #e7eaf2;
  --ok: #2fbf85;
}

* { box-sizing: border-box; }

/* 关键：浏览器默认的 [hidden]{display:none} 会被作者样式里的 display:flex/grid 盖掉，
   凡是用 hidden 属性控制显隐的元素（下拉、答案面板等）都必须靠这条兜底。 */
[hidden] { display: none !important; }

html, body {
  margin: 0;
  height: 100%;
  background: var(--bg);
  color: var(--ink);
  font: 15px/1.6 -apple-system, "Segoe UI", "Microsoft YaHei", system-ui, sans-serif;
  -webkit-font-smoothing: antialiased;
  -webkit-text-size-adjust: 100%;
}
body { -webkit-tap-highlight-color: transparent; }
button, .case-card, .set-head { touch-action: manipulation; }

/* ---------- 顶栏 ---------- */
.top {
  display: flex;
  align-items: center;
  gap: 22px;
  padding: 0 22px;
  height: 58px;
  background: var(--card);
  border-bottom: 1px solid var(--line);
  position: sticky;
  top: 0;
  z-index: 10;
}
.brand { display: flex; align-items: baseline; gap: 8px; }
.logo { font-weight: 800; letter-spacing: .5px; font-size: 18px; }
.brand .sub { color: var(--dim); font-size: 13px; }

.tabs { display: flex; gap: 4px; }
.tab {
  border: 0; background: transparent; color: var(--dim);
  padding: 7px 16px; border-radius: 9px; cursor: pointer;
  font-size: 14px; font-weight: 600; font-family: inherit;
}
.tab:hover { background: var(--card2); color: var(--ink); }
.tab.is-on { background: var(--accent-soft); color: var(--accent); }

.meta { margin-left: auto; }
.pill {
  font-size: 13px; color: var(--dim);
  background: var(--card2); padding: 4px 12px; border-radius: 20px;
}
.pill.has { background: var(--accent-soft); color: var(--accent); font-weight: 600; }

/* ---------- 练习页 ---------- */
.view { max-width: 1080px; margin: 0 auto; padding: 26px 22px 40px; }

.stage {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  min-height: 420px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 40px 26px;
}

.stage-hint { text-align: center; color: var(--dim); }
.stage-hint p { margin: 6px 0; }
.stage-hint .dim { font-size: 13px; }

.stage-body { width: 100%; text-align: center; }

.scramble {
  font-family: Consolas, "Cascadia Mono", "DejaVu Sans Mono", ui-monospace, monospace;
  font-weight: 600;
  font-size: clamp(19px, 3.4vw, 33px);
  line-height: 1.5;
  letter-spacing: .5px;
  word-spacing: 9px;
  margin: 0 auto;
  max-width: 940px;
  user-select: all;
}
.scramble .mv { white-space: nowrap; }

/* 操作按钮：桌面端内嵌快捷键提示，手机端只留文字（见媒体查询） */
.actions {
  margin-top: 30px;
  display: flex;
  gap: 10px;
  justify-content: center;
  flex-wrap: wrap;
}
.btn.big {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 9px;
  padding: 11px 22px;
  font-size: 14.5px;
  border-radius: 10px;
}
.btn.primary { background: var(--accent); color: var(--on-accent); border-color: var(--accent); }
.btn.primary:hover { background: var(--accent-hover); border-color: var(--accent-hover); }
.actions kbd { background: rgba(127, 127, 127, .16); border-color: rgba(127, 127, 127, .28); color: inherit; }
.actions .btn.primary kbd { background: rgba(127, 127, 127, .3); border-color: rgba(127, 127, 127, .45); color: inherit; }

kbd {
  font: 600 12px ui-monospace, Consolas, monospace;
  background: var(--kbd-bg);
  border: 1px solid var(--line);
  border-bottom-width: 2px;
  border-radius: 6px;
  padding: 2px 7px;
  color: var(--kbd-ink);
}

.case-tag {
  margin-top: 18px;
  font-size: 13px;
  color: var(--dim);
}
.case-tag b { color: var(--accent); font-weight: 700; }

/* 答案面板 */
.answer {
  margin-top: 26px;
  width: 100%;
  max-width: 900px;
  border-top: 1px dashed var(--line);
  padding-top: 22px;
  display: flex;
  gap: 26px;
  align-items: flex-start;     /* 魔方图顶部对齐「这条是」那一行 */
  justify-content: center;     /* 图 + 公式整体左右居中 */
  text-align: left;
  flex-wrap: wrap;
}
.answer-fig { margin-top: 2px; flex: none; }
.answer-fig svg { display: block; }
.answer-info { flex: 0 1 auto; min-width: 0; max-width: 100%; }
.answer-row { display: flex; gap: 12px; padding: 3px 0; align-items: baseline; }
.answer-row.row-top { align-items: flex-start; }
.answer-row label { color: var(--dim); font-size: 13px; min-width: 58px; flex: none; }
.alg {
  font: 500 15px/1.5 ui-monospace, Consolas, monospace;
  word-break: break-word;
}
.alg.small { font-size: 12.5px; color: var(--dim); }
/* 全部公式：一条一行，过长自动折行；不设高度上限，让面板自己撑开 */
.alg-list div { line-height: 1.85; padding-left: 10px; text-indent: -10px; }
.alg-list div:hover { color: var(--ink); }

/* ---------- 开关按钮（抽样方式 / 主题） ---------- */
.switch {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: none;
  border: 0;
  margin: 0;
  padding: 0;
  font-family: inherit;
  font-size: 13px;
  color: var(--dim);
  cursor: pointer;
  user-select: none;
  touch-action: manipulation;
}
.switch:hover { color: var(--ink); }
.switch .track {
  flex: none;
  width: 38px;
  height: 22px;
  border-radius: 11px;
  background: var(--track);
  position: relative;
  transition: background .18s ease;
}
.switch .knob {
  position: absolute;
  top: 3px;
  left: 3px;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--knob);
  box-shadow: 0 1px 3px rgba(0, 0, 0, .28);
  transition: transform .18s ease;
}
.switch[aria-checked="true"] .track { background: var(--accent); }
.switch[aria-checked="true"] .knob { transform: translateX(16px); }
.switch:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; border-radius: 8px; }
.switch-label { white-space: nowrap; }

/* 主题开关钉在这一行的最右侧 */
.theme-switch { margin-left: auto; }

.stage-foot {
  display: flex;
  gap: 16px;
  align-items: center;
  padding: 14px 4px 0;
  font-size: 13px;
  color: var(--dim);
}

/* 练习槽位（ZBLS）：勾选框多选，一个都不勾＝只出 FR 槽 */
.slot-picker {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
}
.slot-picker .slot-title { white-space: nowrap; }
.slot-opt {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  cursor: pointer;
  color: var(--ink);
  line-height: 1;
}
.slot-opt input {
  width: 15px;
  height: 15px;
  margin: 0;
  accent-color: var(--accent);
  cursor: pointer;
}
.slot-opt input:checked + span { color: var(--accent); font-weight: 600; }

/* ---------- 选择页 ---------- */
.sel-bar {
  display: flex;
  align-items: center;
  gap: 16px;
  margin-bottom: 16px;
}
.sel-actions { display: flex; gap: 8px; }
.btn {
  /* 注意：不能写 font: 600 13.5px inherit —— inherit 会被当成字体族名，
     结果按钮回退到衬线字体，和页面其它文字不一致。 */
  font-family: inherit;
  font-size: 13.5px;
  font-weight: 600;
  border: 1px solid var(--line);
  background: var(--card);
  color: var(--ink);
  padding: 7px 14px;
  border-radius: 9px;
  cursor: pointer;
}
.btn:hover { border-color: var(--line-strong); background: var(--card3); }
.btn.primary { background: var(--accent); color: var(--on-accent); border-color: var(--accent); }
.btn.mini { padding: 3px 10px; font-size: 12.5px; border-radius: 7px; }

.set-list { display: flex; flex-direction: column; gap: 12px; }

.set-card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
}
.set-head {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 13px 18px;
  cursor: pointer;
}
.set-head:hover { background: var(--card3); }
.set-name { font-weight: 700; font-size: 15px; min-width: 74px; }
.set-name .cnt { color: var(--dim); font-weight: 500; font-size: 12.5px; margin-left: 6px; }
.set-bar {
  flex: 1;
  height: 6px;
  border-radius: 3px;
  background: var(--card2);
  overflow: hidden;
  max-width: 220px;
}
.set-bar i { display: block; height: 100%; background: var(--accent); width: 0; }
.set-state { margin-left: auto; display: flex; align-items: center; gap: 8px; }
.chev { color: var(--dim); transition: transform .18s; font-size: 12px; }
.chev.open { transform: rotate(90deg); }

.sub-list { padding: 4px 18px 18px; display: flex; flex-direction: column; gap: 14px; }
.sub-block { border-top: 1px solid var(--line); padding-top: 12px; }
.sub-head {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 10px;
}
.sub-name { font-weight: 600; font-size: 14px; min-width: 56px; }
.sub-head .dim { font-size: 12.5px; }

.grid {
  display: grid;
  /* 列数由 JS 按子类条数设置（12 条 -> 6 列，8 条 -> 4 列），保证每行都排满 */
  grid-template-columns: repeat(var(--cols, 6), minmax(0, 1fr));
  gap: 10px;
}
@media (max-width: 760px) {
  .grid { grid-template-columns: repeat(auto-fill, minmax(96px, 1fr)); }
}
.case-card {
  border: 1px solid var(--line);
  border-radius: 10px;
  background: var(--card);
  padding: 9px 6px 6px;
  cursor: pointer;
  text-align: center;
  transition: .12s;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 5px;
}
.case-card:hover { border-color: var(--hover-line); transform: translateY(-1px); }
.case-card.on { border-color: var(--accent); background: var(--accent-soft); box-shadow: 0 0 0 1px var(--accent) inset; }
.case-card svg { display: block; max-width: 100%; height: auto; }
.case-card .lbl {
  font: 600 12px ui-monospace, Consolas, monospace;
  color: var(--dim);
}
.case-card.on .lbl { color: var(--accent); }

.dim { color: var(--dim); }

/* ============================================================
 * 手机端适配
 * 放在文件最后，保证能盖住上面的基础样式
 * ============================================================ */
@media (max-width: 760px) {
  /* --- 顶栏 --- */
  .top { gap: 10px; height: 52px; padding: 0 13px; }
  .logo { font-size: 16px; }
  .brand .sub { display: none; }
  .tab { padding: 7px 11px; font-size: 13.5px; border-radius: 8px; }
  .pill { font-size: 12px; padding: 3px 10px; white-space: nowrap; }

  /* --- 通用 --- */
  .view { padding: 14px 12px calc(26px + env(safe-area-inset-bottom)); }

  /* --- 练习页 --- */
  .stage {
    min-height: 0;
    padding: 26px 16px;
    border-radius: 12px;
  }
  .scramble { font-size: clamp(19px, 5.6vw, 26px); word-spacing: 6px; letter-spacing: 0; }

  .actions { margin-top: 22px; gap: 9px; }
  .actions .btn.big {
    flex: 1 1 0;
    padding: 14px 8px;          /* 触摸目标够大 */
    font-size: 15px;
  }
  .actions kbd { display: none; }  /* 手机没物理键盘，不必提示 */

  .case-tag { margin-top: 13px; font-size: 12.5px; }

  /* 解法面板：图在上、文字在下，整块居中 */
  .answer {
    margin-top: 18px;
    padding-top: 16px;
    gap: 14px;
    flex-direction: column;
    align-items: center;
  }
  .answer-fig { margin-top: 0; }
  .answer-info { width: 100%; }
  .answer-row { display: block; padding: 5px 0; }
  .answer-row label { display: block; min-width: 0; font-size: 12px; margin-bottom: 1px; }
  .alg { font-size: 14px; }
  .alg.small { font-size: 12px; }
  .alg-list div { line-height: 1.9; }

  .stage-foot {
    flex-wrap: wrap;
    gap: 8px 14px;
    padding: 12px 2px 0;
    font-size: 12.5px;
  }
  .switch { min-height: 34px; }   /* 触摸目标 */
  .slot-picker { gap: 10px 14px; }
  .slot-opt input { width: 18px; height: 18px; }   /* 触摸目标 */

  /* --- 选择页 --- */
  .sel-bar { flex-wrap: wrap; gap: 10px; margin-bottom: 12px; }
  .set-head { flex-wrap: wrap; gap: 8px 10px; padding: 11px 13px; }
  .set-name { flex: 1 1 auto; min-width: 0; }
  .set-bar { order: 10; flex: 1 1 100%; max-width: none; height: 5px; }
  .set-state { margin-left: auto; }

  .sub-list { padding: 2px 13px 14px; gap: 12px; }
  .sub-head { gap: 8px; margin-bottom: 9px; }
  .grid { grid-template-columns: repeat(auto-fill, minmax(96px, 1fr)); gap: 8px; }
  .case-card { padding: 7px 4px 5px; gap: 4px; }
  .case-card .lbl { font-size: 11px; }
  .btn.mini { padding: 9px 12px; font-size: 12px; }   /* 触摸目标 */
  .btn { padding: 8px 15px; }
}

/* 小屏手机（iPhone SE 一类的 320~400px） */
@media (max-width: 400px) {
  .scramble { font-size: 18px; word-spacing: 4px; }
  .grid { grid-template-columns: repeat(auto-fill, minmax(84px, 1fr)); }
  .logo { font-size: 15px; }
  .tab { padding: 6px 9px; font-size: 13px; }
  .pill { font-size: 11.5px; padding: 3px 8px; }
  .actions .btn.big { font-size: 14px; padding: 13px 6px; }
}

/* 横屏矮屏：别让练习区把按钮挤出屏幕 */
@media (max-height: 520px) and (orientation: landscape) {
  .stage { padding: 18px 16px; }
  .actions { margin-top: 14px; }
}

/* Training mode button sits immediately before Home. */
.mode-button { font: inherit; font-size: 13px; cursor: pointer; }
@media (max-width: 600px) {
  .top .brand .sub { display: none; }
  .top .meta { gap: 6px; }
  .top .meta .home-link { padding: 7px 10px; font-size: 12px; }
  .top .meta .pill { font-size: 11px; padding: 3px 7px; }
}