/* 《Linux 就该这么学》练习系统 · 样式(明暗双主题,移动端适配) */
:root {
  --bg: #f6f7f9; --bg2: #eef0f3; --card: #ffffff; --border: #e3e6ea;
  --fg: #24292f; --muted: #6b7280; --accent: #1f6feb; --accent-weak: #e7f0fe;
  --ok: #1a7f37; --ok-weak: #e3f4e8; --bad: #cf222e; --bad-weak: #fdebec;
  --warn: #9a6700; --warn-weak: #fff3d6;
  --code-bg: #f0f2f5; --code-fg: #24292f; --pre-bg: #1e2430; --pre-fg: #e6edf3;
  --shadow: 0 1px 3px rgba(16, 24, 40, .08), 0 1px 2px rgba(16, 24, 40, .04);
  --radius: 12px;
}
[data-theme="dark"] {
  --bg: #0d1117; --bg2: #10161f; --card: #151c26; --border: #2a3341;
  --fg: #e6edf3; --muted: #8b98a5; --accent: #4a8dff; --accent-weak: #16233a;
  --ok: #3fb950; --ok-weak: #12291a; --bad: #f85149; --bad-weak: #331417;
  --warn: #d29922; --warn-weak: #2d2410;
  --code-bg: #1b2330; --code-fg: #e6edf3; --pre-bg: #0a0e14; --pre-fg: #c9d6e3;
  --shadow: 0 1px 3px rgba(0, 0, 0, .5);
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0; background: var(--bg); color: var(--fg);
  font: 15px/1.75 system-ui, -apple-system, "Segoe UI", "Noto Sans CJK SC",
        "Source Han Sans SC", "Microsoft YaHei", sans-serif;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ---------- 顶栏 ---------- */
.topbar {
  position: sticky; top: 0; z-index: 50; display: flex; align-items: center;
  gap: 12px; padding: 0 16px; height: 56px;
  background: color-mix(in srgb, var(--card) 88%, transparent);
  backdrop-filter: blur(10px); border-bottom: 1px solid var(--border);
}
.brand { font-weight: 700; color: var(--fg); font-size: 15px; white-space: nowrap; }
.brand:hover { text-decoration: none; }
.tabs { display: flex; gap: 4px; margin-left: auto; }
.tabs a {
  padding: 6px 14px; border-radius: 999px; color: var(--muted); font-weight: 600;
}
.tabs a:hover { text-decoration: none; color: var(--fg); background: var(--bg2); }
.tabs a.active { color: #fff; background: var(--accent); }
.iconbtn {
  border: 1px solid var(--border); background: var(--card); color: var(--fg);
  border-radius: 8px; font-size: 16px; width: 34px; height: 34px; cursor: pointer;
}
#menuBtn { display: none; }

/* ---------- 布局 ---------- */
.layout { display: flex; min-height: calc(100vh - 56px); }
.sidebar {
  width: 264px; flex: none; padding: 14px 10px 40px; overflow-y: auto;
  border-right: 1px solid var(--border); background: var(--card);
  max-height: calc(100vh - 56px); position: sticky; top: 56px;
}
.main { flex: 1; min-width: 0; padding: 24px clamp(14px, 4vw, 44px) 80px; }
.backdrop { display: none; }

/* ---------- 侧栏 ---------- */
.sidegroup { margin-bottom: 14px; }
.sidehead {
  font-size: 12px; font-weight: 700; color: var(--muted);
  letter-spacing: .06em; margin: 10px 8px 4px; text-transform: uppercase;
}
.sidehead2 {
  font-size: 12.5px; font-weight: 700; color: var(--fg);
  margin: 8px 8px 2px;
}
.sideitem {
  display: block; padding: 4px 12px; border-radius: 8px; color: var(--muted);
  font-size: 13.5px; line-height: 1.6;
}
.sideitem:hover { background: var(--bg2); color: var(--fg); text-decoration: none; }
.sideitem.active { background: var(--accent-weak); color: var(--accent); font-weight: 600; }

/* ---------- 正文渲染 ---------- */
.doc { max-width: 860px; }
.doc h1 { font-size: 26px; border-bottom: 2px solid var(--border); padding-bottom: 10px; }
.doc h2 { font-size: 20px; margin-top: 34px; }
.doc h3 { font-size: 17px; margin-top: 26px; }
.doc h4 { font-size: 15.5px; }
.doc p, .doc li { overflow-wrap: break-word; }
.doc blockquote {
  margin: 12px 0; padding: 10px 16px; border-left: 4px solid var(--accent);
  background: var(--accent-weak); border-radius: 0 8px 8px 0; color: var(--fg);
}
.doc blockquote p { margin: 4px 0; }
.doc code {
  background: var(--code-bg); color: var(--code-fg); border-radius: 6px;
  padding: 2px 6px; font: 13px/1.6 ui-monospace, "SFMono-Regular", Consolas,
  "Noto Sans Mono CJK SC", monospace;
}
.codeblock {
  margin: 14px 0; border-radius: 10px; overflow: hidden;
  border: 1px solid #2a3341;
}
.codebar {
  display: flex; justify-content: space-between; align-items: center;
  background: #262d3b; color: #9aa7b8; padding: 5px 12px; font-size: 12px;
}
.copybtn {
  background: transparent; color: #c9d6e3; border: 1px solid #3b465a;
  border-radius: 6px; padding: 2px 10px; font-size: 12px; cursor: pointer;
}
.copybtn:hover { background: #3b465a; }
.codeblock pre {
  margin: 0; background: var(--pre-bg); color: var(--pre-fg); padding: 14px 16px;
  overflow-x: auto; font: 13.5px/1.65 ui-monospace, "SFMono-Regular", Consolas,
  "Noto Sans Mono CJK SC", monospace;
}
.codeblock pre code { background: none; color: inherit; padding: 0; }
.tablewrap { overflow-x: auto; margin: 14px 0; border: 1px solid var(--border); border-radius: 10px; }
.doc table { border-collapse: collapse; width: 100%; font-size: 14px; }
.doc th, .doc td { border-bottom: 1px solid var(--border); padding: 8px 12px; text-align: left; }
.doc thead th { background: var(--bg2); font-weight: 700; white-space: nowrap; }
.doc tbody tr:nth-child(even) { background: color-mix(in srgb, var(--bg2) 55%, transparent); }
.doc tbody tr:last-child td { border-bottom: none; }
.doc hr { border: none; border-top: 1px solid var(--border); margin: 26px 0; }
.rocky {
  border: 1px solid color-mix(in srgb, var(--warn) 45%, transparent);
  background: var(--warn-weak); border-radius: 10px;
  padding: 10px 14px; margin: 12px 0; font-size: 14px;
}
.tipbox {
  border: 1px solid color-mix(in srgb, var(--accent) 40%, transparent);
  background: var(--accent-weak); border-radius: 10px;
  padding: 10px 14px; margin: 10px 0 0; font-size: 13.5px;
}
.tipbox b { margin-right: 6px; }
.tipbox p { margin: 4px 0; }
.pager { display: flex; justify-content: space-between; margin-top: 40px; max-width: 860px; }
.pagerbtn {
  border: 1px solid var(--border); background: var(--card); border-radius: 10px;
  padding: 8px 16px; color: var(--fg); font-weight: 600; box-shadow: var(--shadow);
}
.pagerbtn:hover { text-decoration: none; border-color: var(--accent); color: var(--accent); }

/* ---------- 考试 ---------- */
.pagetitle { margin: 4px 0 6px; font-size: 22px; }
.muted { color: var(--muted); font-size: 13.5px; }
.examhead {
  display: flex; justify-content: space-between; align-items: flex-start;
  gap: 16px; position: sticky; top: 56px; z-index: 30;
  background: color-mix(in srgb, var(--bg) 92%, transparent);
  backdrop-filter: blur(8px); padding: 10px 0 8px; margin-bottom: 6px;
  border-bottom: 1px solid var(--border);
}
.timer { font: 700 18px/1.4 ui-monospace, monospace; color: var(--accent); white-space: nowrap; }
.timer.over { color: var(--bad); }
.examsec { margin: 22px 0; }
.examsec > h3 {
  font-size: 16px; padding: 8px 14px; background: var(--bg2);
  border-radius: 10px; border-left: 4px solid var(--accent);
}
.qcard {
  background: var(--card); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px 18px; margin: 14px 0; box-shadow: var(--shadow);
}
.qcard.pending { border-color: color-mix(in srgb, var(--warn) 55%, var(--border)); }
.qcard.wrong { border-left: 4px solid var(--bad); }
.qhead { display: flex; align-items: center; gap: 10px; margin-bottom: 6px; }
.qno {
  background: var(--accent); color: #fff; font-weight: 700; border-radius: 8px;
  min-width: 34px; height: 26px; display: inline-flex; align-items: center;
  justify-content: center; font-size: 13.5px; padding: 0 6px;
}
.qpts { color: var(--muted); font-size: 12.5px; font-weight: 700; }
.qtype {
  font-size: 12px; color: var(--muted); border: 1px solid var(--border);
  border-radius: 999px; padding: 1px 9px;
}
.qstem p { margin: 6px 0; }
.opts { display: grid; gap: 8px; margin-top: 10px; }
.opts.judge { grid-template-columns: 1fr 1fr; max-width: 340px; }
.opt {
  display: flex; gap: 10px; align-items: flex-start; padding: 9px 12px;
  border: 1px solid var(--border); border-radius: 10px; cursor: pointer;
}
.opt:hover { border-color: var(--accent); background: var(--accent-weak); }
.opt input { margin-top: 4px; accent-color: var(--accent); }
.optkey { font-weight: 700; color: var(--accent); }
.blanks { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 10px; }
.blankinput {
  border: 1px solid var(--border); border-radius: 8px; padding: 8px 12px;
  font: inherit; background: var(--bg); color: var(--fg); min-width: 220px;
}
.blankinput:focus, .freeinput:focus, .selfscore input:focus { outline: 2px solid var(--accent); border-color: transparent; }
.freeinput {
  width: 100%; min-height: 90px; margin-top: 10px; resize: vertical;
  border: 1px solid var(--border); border-radius: 10px; padding: 10px 12px;
  font: inherit; background: var(--bg); color: var(--fg);
}
.subparts { margin: 10px 0 0; padding-left: 22px; }
.subparts li { margin: 6px 0; }
.pts { color: var(--muted); font-size: 12.5px; margin-left: 6px; }
.submitbar {
  position: sticky; bottom: 12px; display: flex; gap: 14px; align-items: center;
  background: var(--card); border: 1px solid var(--border); border-radius: 14px;
  padding: 12px 18px; margin-top: 26px; box-shadow: 0 6px 24px rgba(16,24,40,.16);
}
button.primary {
  background: var(--accent); color: #fff; border: none; border-radius: 10px;
  padding: 9px 22px; font: 700 14.5px/1.4 inherit; cursor: pointer;
}
button.primary:hover { filter: brightness(1.08); }
button.primary:disabled { opacity: .55; cursor: not-allowed; }
button.big { padding: 12px 34px; font-size: 16px; }
button.ghost {
  background: var(--card); color: var(--fg); border: 1px solid var(--border);
  border-radius: 10px; padding: 8px 16px; font: 600 13.5px/1.4 inherit; cursor: pointer;
}
button.ghost:hover { border-color: var(--accent); color: var(--accent); }

/* 判分 */
.tag { font-size: 12.5px; font-weight: 700; border-radius: 999px; padding: 2px 10px; }
.tag.good { color: var(--ok); background: var(--ok-weak); }
.tag.bad { color: var(--bad); background: var(--bad-weak); }
.tag.self { color: var(--warn); background: var(--warn-weak); }
.resultline { margin-top: 10px; font-size: 14px; display: flex; flex-wrap: wrap; gap: 8px; align-items: center; }
.blankcheck { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 8px; }
.blankcheck .b {
  border: 1px solid var(--border); border-radius: 8px; padding: 4px 10px; font-size: 13px;
}
.blankcheck .b.ok { border-color: var(--ok); color: var(--ok); }
.blankcheck .b.no { border-color: var(--bad); color: var(--bad); }
.refans {
  margin-top: 12px; border-top: 1px dashed var(--border); padding-top: 10px;
  font-size: 14px;
}
.refans .refhead { font-weight: 700; color: var(--accent); margin-bottom: 4px; }
.refans p { margin: 6px 0; }
.selfscore { display: inline-flex; align-items: center; gap: 8px; margin-top: 12px; font-weight: 600; }
.selfscore input, .selfscore.sub input {
  width: 84px; border: 1px solid var(--border); border-radius: 8px;
  padding: 6px 10px; font: inherit; background: var(--bg); color: var(--fg);
}
.selfscore.sub { display: flex; }
.gradefoot {
  position: sticky; bottom: 12px; display: flex; gap: 16px; align-items: center;
  background: var(--card); border: 1px solid var(--border); border-radius: 14px;
  padding: 12px 18px; margin-top: 26px; box-shadow: 0 6px 24px rgba(16,24,40,.16);
  font-size: 15px;
}
.totalnum { font-size: 22px; font-weight: 800; color: var(--accent); }

/* 结果卡 */
.resultcard {
  max-width: 560px; margin: 40px auto; text-align: center;
  background: var(--card); border: 1px solid var(--border); border-radius: 18px;
  padding: 34px 30px; box-shadow: var(--shadow);
}
.score { font-size: 64px; font-weight: 800; line-height: 1.1; }
.score.ok { color: var(--ok); }
.score.no { color: var(--warn); }
.verdict { font-size: 17px; font-weight: 700; margin: 6px 0 2px; }
.resultcard .actions { display: flex; gap: 10px; justify-content: center; margin-top: 22px; flex-wrap: wrap; }

/* ---------- 考试列表 ---------- */
.examgrid { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 12px; margin-top: 18px; }
.examcard {
  background: var(--card); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px; color: var(--fg); box-shadow: var(--shadow); transition: transform .12s, border-color .12s;
}
.examcard:hover { text-decoration: none; transform: translateY(-2px); border-color: var(--accent); }
.examtitle { font-weight: 700; line-height: 1.5; }
.best { margin-top: 10px; font-size: 13px; font-weight: 700; }
.best.ok { color: var(--ok); }
.best.no { color: var(--warn); }
.best.none { color: var(--muted); font-weight: 500; }

/* ---------- 复习 ---------- */
.subtabs { display: flex; gap: 8px; margin: 6px 0 18px; flex-wrap: wrap; }
.subtabs a {
  padding: 6px 16px; border-radius: 999px; border: 1px solid var(--border);
  color: var(--muted); font-weight: 600; font-size: 13.5px;
}
.subtabs a.active { background: var(--accent); border-color: var(--accent); color: #fff; }
.subtabs a:hover { text-decoration: none; color: var(--fg); }
.select {
  border: 1px solid var(--border); border-radius: 10px; padding: 8px 12px;
  font: inherit; background: var(--card); color: var(--fg); margin-bottom: 14px;
}
.refline { margin-top: 10px; font-size: 14px; }
.empty {
  border: 1px dashed var(--border); border-radius: var(--radius);
  padding: 40px 20px; text-align: center; color: var(--muted); margin-top: 18px;
}
.attempt { display: flex; justify-content: space-between; gap: 10px; padding: 9px 4px; border-bottom: 1px solid var(--border); font-size: 14px; }
.attempt:last-child { border-bottom: none; }

/* ---------- toast ---------- */
.toast {
  position: fixed; left: 50%; bottom: 28px; transform: translateX(-50%) translateY(20px);
  background: var(--fg); color: var(--bg); border-radius: 10px; padding: 10px 20px;
  font-size: 14px; font-weight: 600; opacity: 0; pointer-events: none;
  transition: all .25s; z-index: 99;
}
.toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }
.toast.err { background: var(--bad); color: #fff; }

/* ---------- 移动端 ---------- */
@media (max-width: 900px) {
  #menuBtn { display: inline-block; }
  .tabs { margin-left: auto; }
  .tabs a { padding: 6px 10px; font-size: 13.5px; }
  .brand { font-size: 13.5px; }
  .sidebar {
    position: fixed; left: 0; top: 56px; bottom: 0; z-index: 60;
    transform: translateX(-105%); transition: transform .22s ease;
    box-shadow: 0 8px 30px rgba(0,0,0,.25); width: 280px;
  }
  .sidebar.open { transform: translateX(0); }
  .backdrop.show { display: block; position: fixed; inset: 56px 0 0 0; background: rgba(0,0,0,.4); z-index: 55; }
  .main { padding: 16px 14px 90px; }
  .examhead { flex-wrap: wrap; }
  .opts.judge { max-width: none; }
}