/* 刷题 · 手机优先；配色参照课程平台（深蓝顶栏、蓝色主按钮、绿对红错） */
:root {
  --navy: #2B3050;
  --navy-2: #383E63;
  --blue: #3D7BF7;
  --blue-soft: #E8F0FE;
  --green: #17B26A;
  --green-soft: #E7F7EF;
  --red: #F04A5E;
  --red-soft: #FDECEE;
  --amber: #C27A00;
  --amber-soft: #FFF4DE;
  --bg: #F3F5F9;
  --card: #FFFFFF;
  --fg: #1F2433;
  --fg-2: #5B6275;
  --fg-3: #8A91A3;
  --line: #E4E7EE;
  --chip: #EEF1F6;
  --safe-t: env(safe-area-inset-top, 0px);
  --safe-b: env(safe-area-inset-bottom, 0px);
  --fs: 17px;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root {
    --navy: #1A1E33; --navy-2: #262B45; --blue: #5B8FFA; --blue-soft: #1D2A48;
    --green: #2FC47F; --green-soft: #13301F; --red: #FF6275; --red-soft: #3A1A20; --amber: #F2B24A; --amber-soft: #3A2C12;
    --bg: #11131C; --card: #1B1E2B; --fg: #E6E8EF; --fg-2: #A7ADBD; --fg-3: #7C8397; --line: #2A2E3E; --chip: #242838;
    color-scheme: dark;
  }
}

* { box-sizing: border-box; -webkit-tap-highlight-color: transparent; }
html, body { margin: 0; background: var(--bg); color: var(--fg); }
body { font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif; min-height: 100vh; }
button { font: inherit; color: inherit; cursor: pointer; touch-action: manipulation; }
a { color: inherit; text-decoration: none; }
.hidden { display: none !important; }
.boot { padding: 40vh 20px; text-align: center; color: var(--fg-3); }

/* ---------- 顶栏 ---------- */
.top {
  position: sticky; top: 0; z-index: 20; display: flex; align-items: center; gap: 10px;
  padding: calc(10px + var(--safe-t)) 14px 10px; background: var(--navy); color: #fff;
}
.top h1 { flex: 1; min-width: 0; margin: 0; font-size: 17px; font-weight: 600; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.top .back { flex: none; font-size: 26px; line-height: 1; padding: 2px 8px 4px 0; }
.top .timer { flex: none; font-variant-numeric: tabular-nums; font-size: 14px; opacity: .85; }
.top .tbtn { flex: none; border: 1px solid rgba(255, 255, 255, .45); background: none; color: #fff; border-radius: 8px; padding: 5px 10px; font-size: 13px; }

/* ---------- 首页 ---------- */
.hero { background: var(--navy); color: #fff; padding: calc(18px + var(--safe-t)) 18px 58px; }
.hero h1 { margin: 0; font-size: 24px; letter-spacing: .04em; }
.hero p { margin: 6px 0 0; font-size: 13px; opacity: .72; }
.stats { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; margin: -42px 14px 0; }
.stat { background: var(--card); border-radius: 12px; padding: 12px 10px; text-align: center; box-shadow: 0 6px 18px -12px rgba(20, 30, 60, .35); }
.stat b { display: block; font-size: 22px; font-variant-numeric: tabular-nums; }
.stat span { font-size: 12px; color: var(--fg-3); }
.quick { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; margin: 14px 14px 4px; }
.qk { display: flex; flex-direction: column; gap: 4px; padding: 14px; border-radius: 12px; background: var(--card); border: 0; text-align: left; }
.qk b { font-size: 16px; }
.qk span { font-size: 12px; color: var(--fg-3); }
.qk.red b { color: var(--red); }
.qk.blue b { color: var(--blue); }
.qk.green b { color: var(--green); }
.qk.amber b { color: var(--amber); }
.sec { margin: 18px 18px 8px; font-size: 13px; color: var(--fg-3); letter-spacing: .08em; }
.list { margin: 0 14px; border-radius: 12px; background: var(--card); overflow: hidden; }
.row { display: flex; align-items: center; gap: 12px; padding: 14px 14px; border-bottom: 1px solid var(--line); }
.row:last-child { border-bottom: 0; }
.row .no { flex: none; width: 40px; height: 40px; border-radius: 10px; display: grid; place-items: center; background: var(--blue-soft); color: var(--blue); font-weight: 700; font-variant-numeric: tabular-nums; }
.row .rt { flex: 1; min-width: 0; }
.row .rt b { display: block; font-size: 15px; font-weight: 600; }
.row .rt small { font-size: 12px; color: var(--fg-3); }
.pill { flex: none; font-size: 12px; padding: 3px 9px; border-radius: 10px; background: var(--chip); color: var(--fg-2); font-variant-numeric: tabular-nums; }
.pill.doing { background: var(--blue-soft); color: var(--blue); }
.pill.good { background: var(--green-soft); color: var(--green); }
.pill.bad { background: var(--red-soft); color: var(--red); }
.foot { margin: 20px 18px calc(30px + var(--safe-b)); font-size: 12px; line-height: 1.7; color: var(--fg-3); }
.foot b { color: var(--fg-2); }

/* ---------- 做题页 ---------- */
.summary { margin: 12px 14px 0; padding: 14px 16px; border-radius: 12px; background: var(--card); font-size: 14px; line-height: 1.9; }
.summary b { font-variant-numeric: tabular-nums; }
.summary .r { color: var(--red); font-weight: 700; }
.summary .g { color: var(--green); font-weight: 700; }
.modebar { display: flex; gap: 8px; align-items: center; margin: 12px 14px 0; flex-wrap: wrap; }
.seg { display: inline-flex; padding: 2px; border-radius: 10px; background: var(--chip); }
.seg button { border: 0; background: none; padding: 6px 12px; border-radius: 8px; font-size: 13px; color: var(--fg-2); }
.seg button.on { background: var(--card); color: var(--fg); font-weight: 600; box-shadow: 0 1px 3px rgba(0, 0, 0, .12); }
.sw { display: inline-flex; align-items: center; gap: 6px; font-size: 13px; color: var(--fg-2); margin-left: auto; }
.sw input { width: 18px; height: 18px; accent-color: var(--blue); }
.qlist { padding: 4px 0 calc(90px + var(--safe-b)); }
.qc { margin: 12px 14px 0; padding: 14px 14px 12px; border-radius: 12px; background: var(--card); border: 1px dashed transparent; scroll-margin-top: calc(70px + var(--safe-t)); }
.qc.ok { border-color: var(--green); }
.qc.bad { border-color: var(--red); }
.qh { display: flex; align-items: center; gap: 8px; }
.qn { min-width: 34px; height: 30px; padding: 0 6px; border-radius: 7px; display: grid; place-items: center; background: var(--navy-2); color: #fff; font-weight: 700; font-size: 15px; font-variant-numeric: tabular-nums; }
.qc.ok .qn { background: var(--green); }
.qc.bad .qn { background: var(--red); }
.qt { font-size: 12px; font-weight: 600; padding: 3px 8px; border-radius: 6px; background: var(--green-soft); color: var(--fg-2); }
.qt.m { background: var(--amber-soft); }
.qt.j { background: var(--blue-soft); }
.qh .src { margin-left: auto; font-size: 11px; color: var(--fg-3); }
.qh .src.ai { color: var(--amber); }
.qs { margin: 12px 2px 10px; font-size: var(--fs); line-height: 1.65; }
.opts { list-style: none; margin: 0; padding: 8px 0 0; border-top: 1px dashed var(--line); }
.op { display: flex; align-items: flex-start; gap: 10px; padding: 10px 6px; border-radius: 8px; font-size: calc(var(--fs) - 1px); line-height: 1.5; cursor: pointer; user-select: none; -webkit-user-select: none; }
.op:active { background: var(--chip); }
.op .mk { flex: none; width: 24px; height: 24px; margin-top: 1px; border-radius: 50%; border: 1.5px solid var(--fg-3); display: grid; place-items: center; font-size: 12px; font-weight: 700; color: var(--fg-3); }
.qc.t-m .op .mk { border-radius: 6px; }
.op.sel .mk { background: var(--blue); border-color: var(--blue); color: #fff; }
.op.sel .ot { color: var(--blue); }
.op .res { flex: none; margin-left: auto; font-style: normal; font-weight: 700; }
.op.right .ot { color: var(--green); font-weight: 600; }
.op.right .res { color: var(--green); }
.op.wrong .ot { color: var(--red); }
.op.wrong .res { color: var(--red); }
.op.wrong .mk { background: var(--red); border-color: var(--red); color: #fff; }
.op.right.sel .mk { background: var(--green); border-color: var(--green); }
.locked .op { cursor: default; }
.locked .op:active { background: none; }
.confirm { margin: 6px 0 2px 40px; border: 0; border-radius: 8px; padding: 8px 16px; background: var(--blue); color: #fff; font-size: 14px; }
.confirm:disabled { opacity: .4; }
.ans { margin-top: 8px; padding: 8px 10px; border-radius: 8px; background: var(--chip); font-size: 13px; line-height: 1.6; color: var(--fg-2); }
.ans b { color: var(--green); }
.ans .ai { color: var(--amber); }
.qa { display: flex; gap: 8px; margin-top: 8px; }
.qa button { border: 1px solid var(--line); background: none; border-radius: 8px; padding: 5px 10px; font-size: 12px; color: var(--fg-2); }
.more { padding: 20px; text-align: center; color: var(--fg-3); font-size: 13px; }

/* 底栏 */
.bottom {
  position: fixed; left: 0; right: 0; bottom: 0; z-index: 20; display: flex; gap: 10px; align-items: center;
  padding: 10px 14px calc(10px + var(--safe-b)); background: var(--card); box-shadow: 0 -6px 20px -14px rgba(0, 0, 0, .45);
}
.bottom .card-btn { flex: 1; display: flex; align-items: center; gap: 8px; border: 0; background: var(--chip); border-radius: 10px; padding: 11px 14px; font-size: 15px; text-align: left; }
.bottom .card-btn small { margin-left: auto; color: var(--fg-3); font-variant-numeric: tabular-nums; }
.bottom .main { flex: none; border: 0; border-radius: 10px; padding: 11px 22px; background: var(--blue); color: #fff; font-size: 15px; font-weight: 600; }
.bottom .ghost { flex: none; border: 1px solid var(--line); border-radius: 10px; padding: 10px 14px; background: none; font-size: 14px; }

/* 答题卡（底部弹出） */
.mask { position: fixed; inset: 0; z-index: 40; background: rgba(10, 14, 28, .45); display: flex; align-items: flex-end; }
.sheet { width: 100%; max-height: 80vh; overflow-y: auto; background: var(--card); border-radius: 16px 16px 0 0; padding: 16px 16px calc(18px + var(--safe-b)); }
.sheet h3 { display: flex; align-items: baseline; margin: 0 0 6px; font-size: 17px; }
.sheet h3 small { margin-left: auto; font-size: 13px; font-weight: 400; color: var(--fg-3); }
.legend { display: flex; gap: 12px; font-size: 12px; color: var(--fg-3); margin-bottom: 4px; }
.legend i { display: inline-block; width: 10px; height: 10px; border-radius: 3px; margin-right: 4px; vertical-align: -1px; }
.grp { margin-top: 12px; font-size: 13px; color: var(--fg-3); }
.grp b { font-size: 17px; color: var(--fg); margin: 0 3px; }
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(44px, 1fr)); gap: 8px; margin-top: 8px; }
.cell { height: 40px; border: 0; border-radius: 8px; background: var(--chip); color: var(--fg-2); font-weight: 600; font-variant-numeric: tabular-nums; }
.cell.done { background: var(--blue); color: #fff; }
.cell.ok { background: var(--green); color: #fff; }
.cell.bad { background: var(--red); color: #fff; }
.sheet-btns { display: flex; gap: 10px; margin-top: 16px; }
.sheet-btns button { flex: 1; border: 0; border-radius: 10px; padding: 12px; font-size: 15px; background: var(--chip); }
.sheet-btns .primary { background: var(--blue); color: #fff; font-weight: 600; }
.sheet p { font-size: 14px; line-height: 1.7; color: var(--fg-2); }

.toast { position: fixed; left: 50%; top: calc(70px + var(--safe-t)); transform: translateX(-50%); z-index: 60; max-width: 86vw;
  background: rgba(20, 24, 40, .92); color: #fff; padding: 10px 16px; border-radius: 10px; font-size: 14px; }
.empty { padding: 60px 24px; text-align: center; color: var(--fg-3); line-height: 1.8; }

@media (min-width: 760px) {
  .qc, .summary, .modebar, .list, .quick, .stats { max-width: 760px; margin-left: auto; margin-right: auto; }
  .bottom { padding-left: max(14px, calc(50% - 366px)); padding-right: max(14px, calc(50% - 366px)); }
}

/* ---------- 首页：继续上次、搜题 ---------- */
.hero-row { display: flex; align-items: center; }
.hero-row h1 { flex: 1; }
.hero-search { flex: none; padding: 5px 12px; border: 1px solid rgba(255, 255, 255, .45); border-radius: 16px; font-size: 13px; }
.resume { display: flex; align-items: center; gap: 10px; margin: 12px 14px 0; padding: 12px 14px; border-radius: 12px; background: var(--blue); color: #fff; }
.resume span { flex: 1; min-width: 0; font-size: 13px; opacity: .92; }
.resume span b { display: block; font-size: 16px; opacity: 1; }
.resume small { font-size: 12px; opacity: .85; }
.resume i { font-style: normal; font-size: 22px; line-height: 1; }
.qk.navy b { color: var(--navy-2); }
@media (prefers-color-scheme: dark) { .qk.navy b { color: #9EA8FF; } }
.row .no.red { background: var(--red-soft); color: var(--red); }

/* ---------- 做题页：边做边看对错 ---------- */
.live { display: flex; flex-wrap: wrap; gap: 6px 16px; margin: 12px 14px 0; padding: 10px 14px; border-radius: 12px; background: var(--card); font-size: 13px; color: var(--fg-2); }
.live b { font-variant-numeric: tabular-nums; color: var(--fg); }
.live .g b { color: var(--green); }
.live .r b { color: var(--red); }
.qh .src.bad { color: var(--red); }
.cell.here { box-shadow: 0 0 0 2px var(--fg); }
.sheet-btns.col { flex-direction: column; }

/* ---------- 错题榜、错题卷、搜题 ---------- */
.rank-head { margin: 12px 14px 0; padding: 14px; border-radius: 12px; background: var(--card); }
.rank-head p { margin: 0 0 12px; font-size: 13px; line-height: 1.7; color: var(--fg-2); }
.rank-head p:last-child { margin-bottom: 0; }
.rank-head b { color: var(--fg); }
.rank-head .r, .rk-meta .r { color: var(--red); }
.btn-main { display: block; width: 100%; border: 0; border-radius: 10px; padding: 12px; background: var(--blue); color: #fff; font-size: 15px; font-weight: 600; text-align: center; }
.empty .btn-main { width: auto; display: inline-block; margin-top: 14px; padding: 10px 28px; }
.tabs { display: flex; gap: 8px; margin: 12px 14px 0; overflow-x: auto; }
.tabs button { flex: none; border: 0; border-radius: 16px; padding: 7px 12px; background: var(--chip); font-size: 13px; color: var(--fg-2); }
.tabs button small { margin-left: 4px; font-variant-numeric: tabular-nums; opacity: .8; }
.tabs button.on { background: var(--navy-2); color: #fff; }
.rank-list { padding: 4px 0 calc(30px + var(--safe-b)); }
.rk { margin: 10px 14px 0; padding: 12px; border-radius: 12px; background: var(--card); }
.rk-top { display: flex; gap: 10px; cursor: pointer; }
.rk-no { flex: none; width: 28px; height: 28px; border-radius: 8px; display: grid; place-items: center; background: var(--chip); color: var(--fg-2); font-weight: 700; font-size: 13px; font-variant-numeric: tabular-nums; }
.rk-no.top3 { background: var(--red); color: #fff; }
.rk-main { flex: 1; min-width: 0; }
.rk-q { margin: 2px 0 6px; font-size: 15px; line-height: 1.6; }
.rk:not(.open) .rk-q { display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden; }
.rk-meta { display: flex; flex-wrap: wrap; align-items: center; gap: 4px 10px; font-size: 12px; color: var(--fg-3); }
.rk-body:empty { display: none; }
.rk-body { margin-top: 8px; }
.rk .op { cursor: default; font-size: 14px; }
.rk .op:active { background: none; }
.search { margin: 12px 14px 0; }
.search input { width: 100%; border: 1px solid var(--line); border-radius: 10px; padding: 11px 14px; font: inherit; font-size: 16px; background: var(--card); color: var(--fg); }
@media (min-width: 760px) {
  .resume, .live, .rank-head, .tabs, .rk, .search { max-width: 760px; margin-left: auto; margin-right: auto; }
}
.tabs { scrollbar-width: none; }
.tabs::-webkit-scrollbar { display: none; }
.summary .sub { font-size: 13px; color: var(--fg-3); }
.sum-btn { display: block; margin-top: 8px; border: 1px solid var(--line); background: none; border-radius: 8px; padding: 6px 14px; font-size: 13px; color: var(--fg-2); }
.bottom .card-btn { min-width: 0; white-space: nowrap; }
.bottom .card-btn small { overflow: hidden; text-overflow: ellipsis; }
.bottom .main { padding: 11px 18px; }

/* ---------- 第三轮：收藏、做题记录标签 ---------- */
.qh .tags { margin-left: auto; display: inline-flex; gap: 6px; align-items: center; }
.qh .tags .src { margin-left: 0; }
.qh .src.good { color: var(--green); }
.star { flex: none; border: 0; background: none; padding: 2px 4px; font-size: 20px; line-height: 1; color: var(--fg-3); }
.star.on { color: #F5A623; }
.rk-meta .star { margin-left: auto; font-size: 18px; }
.sec.sub { margin-top: 10px; font-size: 12px; }
mark { background: #FFE58A; color: inherit; border-radius: 3px; padding: 0 1px; }
@media (prefers-color-scheme: dark) { mark { background: #6B5A12; } }
.stat span { display: block; white-space: nowrap; }
.ans .jx { margin-top: 6px; padding-top: 6px; border-top: 1px dashed var(--line); color: var(--fg); font-size: 14px; line-height: 1.7; }
.ans .jx b { display: inline-block; margin-right: 6px; padding: 0 6px; border-radius: 4px; font-size: 12px; color: #fff; background: var(--blue); }