/* 元AI 学习卡 · 知识题库 —— 暗色优先，移动端优先 */
:root {
  --bg: #0b1020;
  --bg-soft: #131a2e;
  --card: #17203a;
  --card-hi: #1d2846;
  --line: #26314f;
  --text: #e8edf9;
  --dim: #94a3c0;
  --dim2: #6b7a9c;
  --brand: #5b8cff;
  --brand-2: #7c5cff;
  --ok: #34d399;
  --warn: #fbbf24;
  --bad: #f87171;
  --radius: 14px;
  --shadow: 0 8px 28px rgba(0, 0, 0, .28);
}

@media (prefers-color-scheme: light) {
  :root {
    --bg: #f5f7fc;
    --bg-soft: #ffffff;
    --card: #ffffff;
    --card-hi: #f0f4ff;
    --line: #dfe6f3;
    --text: #1a2233;
    --dim: #5a6a86;
    --dim2: #8494ad;
    --shadow: 0 6px 20px rgba(26, 34, 51, .08);
  }
}

* { box-sizing: border-box; }

/* hidden 必须始终生效（.review-grades 等设了 display 的元素也要能被隐藏） */
[hidden] { display: none !important; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", "Source Han Sans SC", sans-serif;
  -webkit-font-smoothing: antialiased;
  line-height: 1.65;
}

a { color: var(--brand); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ---------- 顶部 ---------- */
.top {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  flex-wrap: wrap;
  gap: 12px 24px;
  align-items: center;
  justify-content: space-between;
  padding: 14px max(18px, env(safe-area-inset-left)) 14px max(18px, env(safe-area-inset-right));
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--line);
}

.brand { display: flex; align-items: center; gap: 12px; min-width: 0; }
.logo { font-size: 26px; line-height: 1; }
.brand h1 {
  margin: 0;
  font-size: 18px;
  font-weight: 650;
  letter-spacing: .2px;
  white-space: nowrap;
}
.sub { margin: 2px 0 0; font-size: 12.5px; color: var(--dim); }

.tabs { display: flex; gap: 4px; background: var(--bg-soft); padding: 4px; border-radius: 999px; border: 1px solid var(--line); }
.tab {
  border: 0;
  background: transparent;
  color: var(--dim);
  font: inherit;
  font-size: 14px;
  padding: 7px 16px;
  border-radius: 999px;
  cursor: pointer;
  transition: .18s;
  white-space: nowrap;
}
.tab:hover { color: var(--text); }
.tab.active { background: linear-gradient(135deg, var(--brand), var(--brand-2)); color: #fff; box-shadow: 0 4px 14px rgba(91, 140, 255, .34); }

/* ---------- 主体 ---------- */
main { max-width: 1080px; margin: 0 auto; padding: 20px 18px 64px; }
.view { display: none; animation: fade .22s ease; }
.view.active { display: block; }
@keyframes fade { from { opacity: 0; transform: translateY(6px); } to { opacity: 1; transform: none; } }

h2 { font-size: 20px; margin: 0 0 4px; }
h3 { font-size: 15px; color: var(--dim); margin: 28px 0 12px; letter-spacing: .3px; }

/* ---------- 工具条 ---------- */
.toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  align-items: center;
  margin-bottom: 16px;
}
.toolbar input[type="search"], .toolbar select {
  font: inherit;
  font-size: 14px;
  color: var(--text);
  background: var(--bg-soft);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 9px 13px;
  outline: none;
  transition: .16s;
}
.toolbar input[type="search"] { flex: 1 1 260px; min-width: 200px; }
.toolbar input[type="search"]:focus, .toolbar select:focus { border-color: var(--brand); box-shadow: 0 0 0 3px rgba(91, 140, 255, .16); }
.count { font-size: 13px; color: var(--dim); margin-left: auto; }

/* ---------- 卡片 ---------- */
.cards { display: grid; gap: 12px; }
@media (min-width: 760px) { .cards { grid-template-columns: 1fr 1fr; } }

.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 15px 16px;
  box-shadow: var(--shadow);
  transition: .18s;
}
.card:hover { border-color: color-mix(in srgb, var(--brand) 42%, var(--line)); transform: translateY(-1px); }
.card .meta { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 8px; }
.card .body { font-size: 14px; color: var(--text); white-space: pre-wrap; word-break: break-word; }
.card .body h2, .card .body h3, .card .body h4 { font-size: 15px; margin: 6px 0 4px; color: var(--text); }
.card .body li { margin-left: 2px; }
.card .body code, .quiz-stem code, .review-answer code {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: .92em;
  background: var(--card-hi);
  padding: 1px 5px;
  border-radius: 5px;
}
.card .body table, .review-answer table {
  width: 100%;
  border-collapse: collapse;
  margin: 8px 0;
  font-size: 13px;
}
.card .body th, .card .body td, .review-answer th, .review-answer td {
  border: 1px solid var(--line);
  padding: 5px 8px;
  text-align: left;
  vertical-align: top;
}
.card .body th, .review-answer th { background: var(--card-hi); font-weight: 600; }
.card .body hr { border: 0; border-top: 1px solid var(--line); margin: 10px 0; }

.chip {
  display: inline-block;
  font-size: 11.5px;
  padding: 2px 9px;
  border-radius: 999px;
  background: rgba(91, 140, 255, .16);
  color: var(--brand);
  border: 1px solid rgba(91, 140, 255, .28);
  white-space: nowrap;
}
.chip.ghost { background: transparent; color: var(--dim); border-color: var(--line); }
.chip.ok { background: rgba(52, 211, 153, .14); color: var(--ok); border-color: rgba(52, 211, 153, .3); }
.chip.bad { background: rgba(248, 113, 113, .14); color: var(--bad); border-color: rgba(248, 113, 113, .3); }

.more-wrap { text-align: center; margin-top: 18px; }

/* ---------- 按钮 ---------- */
.btn {
  font: inherit;
  font-size: 14px;
  padding: 9px 18px;
  border-radius: 10px;
  border: 1px solid transparent;
  background: linear-gradient(135deg, var(--brand), var(--brand-2));
  color: #fff;
  cursor: pointer;
  transition: .16s;
  box-shadow: 0 4px 16px rgba(91, 140, 255, .26);
}
.btn:hover { transform: translateY(-1px); filter: brightness(1.06); }
.btn:active { transform: none; }
.btn.ghost { background: var(--bg-soft); color: var(--text); border-color: var(--line); box-shadow: none; }
.btn.ghost:hover { border-color: var(--brand); }
.btn.small { padding: 6px 12px; font-size: 13px; }
.btn.danger { color: var(--bad); border-color: rgba(248, 113, 113, .36); }
.btn:disabled { opacity: .5; cursor: not-allowed; transform: none; }

/* ---------- 刷题 ---------- */
.quiz-head { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; justify-content: space-between; margin-bottom: 14px; }
.quiz-meta, .quiz-actions { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; }

.quiz-card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 18px;
  padding: 22px;
  box-shadow: var(--shadow);
}
.quiz-stem {
  margin: 0 0 16px;
  font-size: 17px;
  line-height: 1.8;
  white-space: pre-wrap;
  word-break: break-word;
}
.quiz-stem .blank {
  display: inline-block;
  min-width: 64px;
  border-bottom: 2px solid var(--brand);
  color: var(--brand);
  text-align: center;
  font-weight: 600;
  letter-spacing: 1px;
}
.quiz-stem mark {
  background: rgba(251, 191, 36, .22);
  color: var(--warn);
  padding: 0 4px;
  border-radius: 4px;
}
.quiz-stem mark.ok { background: rgba(52, 211, 153, .2); color: var(--ok); }

#quiz-body input[type="text"] {
  width: 100%;
  font: inherit;
  font-size: 15px;
  padding: 11px 14px;
  border-radius: 10px;
  border: 1px solid var(--line);
  background: var(--bg-soft);
  color: var(--text);
  outline: none;
}
#quiz-body input[type="text"]:focus { border-color: var(--brand); box-shadow: 0 0 0 3px rgba(91, 140, 255, .16); }

.options { display: grid; gap: 9px; }
.option {
  display: flex;
  gap: 10px;
  align-items: flex-start;
  width: 100%;
  text-align: left;
  font: inherit;
  font-size: 15px;
  color: var(--text);
  background: var(--bg-soft);
  border: 1px solid var(--line);
  border-radius: 11px;
  padding: 12px 14px;
  cursor: pointer;
  transition: .15s;
}
.option:hover { border-color: var(--brand); }
.option .key { color: var(--dim2); font-variant-numeric: tabular-nums; min-width: 16px; }
.option.sel { border-color: var(--brand); background: rgba(91, 140, 255, .12); }
.option.right { border-color: var(--ok); background: rgba(52, 211, 153, .13); }
.option.wrong { border-color: var(--bad); background: rgba(248, 113, 113, .12); }

.quiz-feedback { margin-top: 14px; font-size: 14.5px; min-height: 22px; }
.quiz-feedback.ok { color: var(--ok); }
.quiz-feedback.bad { color: var(--bad); }
.quiz-feedback .answer { color: var(--text); }

.quiz-foot { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; margin-top: 18px; }
.hint { font-size: 12.5px; color: var(--dim2); }
kbd {
  font-family: ui-monospace, Menlo, Consolas, monospace;
  font-size: 11.5px;
  border: 1px solid var(--line);
  border-bottom-width: 2px;
  border-radius: 5px;
  padding: 1px 5px;
  color: var(--dim);
}

/* ---------- 复习 ---------- */
.review-head { display: flex; flex-wrap: wrap; gap: 16px; align-items: flex-end; justify-content: space-between; margin-bottom: 16px; }
.review-nums { display: flex; gap: 22px; }
.num { text-align: center; }
.num b { display: block; font-size: 22px; font-variant-numeric: tabular-nums; }
.num span { font-size: 12px; color: var(--dim); }

.review-label { margin: 0 0 10px; font-size: 12.5px; color: var(--dim); letter-spacing: .3px; }
.review-answer {
  margin-top: 14px;
  padding: 15px;
  border-radius: 12px;
  background: var(--bg-soft);
  border: 1px dashed var(--line);
  font-size: 14.5px;
  white-space: pre-wrap;
  word-break: break-word;
  max-height: 46vh;
  overflow: auto;
}
.review-grades { display: grid; grid-template-columns: repeat(2, 1fr); gap: 9px; margin-top: 16px; }
@media (min-width: 560px) { .review-grades { grid-template-columns: repeat(4, 1fr); } }
.grade { display: flex; flex-direction: column; gap: 2px; align-items: center; background: var(--bg-soft); border: 1px solid var(--line); color: var(--text); box-shadow: none; }
.grade small { font-size: 11px; color: var(--dim); font-weight: 400; }
.grade.again:hover { border-color: var(--bad); }
.grade.hard:hover { border-color: var(--warn); }
.grade.good:hover { border-color: var(--brand); }
.grade.easy:hover { border-color: var(--ok); }

.review-empty { text-align: center; padding: 46px 16px; color: var(--dim); }
.review-foot { margin-top: 18px; }

/* ---------- 进度 ---------- */
.stat-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 12px; }
@media (min-width: 720px) { .stat-grid { grid-template-columns: repeat(3, 1fr); } }
.stat-box {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 16px;
  text-align: center;
  box-shadow: var(--shadow);
}
.stat-box b { display: block; font-size: 26px; font-variant-numeric: tabular-nums; background: linear-gradient(135deg, var(--brand), var(--brand-2)); -webkit-background-clip: text; background-clip: text; color: transparent; }
.stat-box span { font-size: 12.5px; color: var(--dim); }

.source-bars { display: grid; gap: 9px; }
.bar-row { display: grid; grid-template-columns: 108px 1fr 46px; gap: 10px; align-items: center; font-size: 13px; }
.bar-track { height: 8px; border-radius: 999px; background: var(--bg-soft); border: 1px solid var(--line); overflow: hidden; }
.bar-fill { height: 100%; border-radius: 999px; background: linear-gradient(90deg, var(--brand), var(--brand-2)); }
.bar-row .n { color: var(--dim); text-align: right; font-variant-numeric: tabular-nums; }

.small-cards .card { padding: 12px 14px; }
.danger-zone { margin-top: 34px; display: flex; flex-wrap: wrap; gap: 12px; align-items: center; }

/* ---------- 页脚 ---------- */
.foot {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  justify-content: center;
  align-items: center;
  padding: 22px 16px 34px;
  font-size: 12.5px;
  color: var(--dim2);
  border-top: 1px solid var(--line);
}
.dot { opacity: .5; }

/* ---------- toast ---------- */
.toast {
  position: fixed;
  left: 50%;
  bottom: 26px;
  transform: translateX(-50%) translateY(10px);
  background: var(--card-hi);
  border: 1px solid var(--line);
  color: var(--text);
  font-size: 14px;
  padding: 10px 18px;
  border-radius: 999px;
  box-shadow: var(--shadow);
  opacity: 0;
  transition: .22s;
  z-index: 40;
  max-width: 86vw;
}
.toast.show { opacity: 1; transform: translateX(-50%); }

@media (max-width: 560px) {
  .brand h1 { font-size: 16px; }
  .sub { display: none; }
  .tab { padding: 6px 12px; font-size: 13px; }
  .quiz-card { padding: 16px; }
  .quiz-stem { font-size: 16px; }
  main { padding: 16px 12px 56px; }
}