:root {
  --bg: #111318;
  --bg2: #1a1d24;
  --bg3: #232733;
  --fg: #e6e8ee;
  --fg2: #9aa1b0;
  --accent: #4f8cff;
  --green: #2ecc71;
  --red: #e74c3c;
  --amber: #f1c40f;
  --border: #2c313d;
  --radius: 10px;
}
@media (prefers-color-scheme: light) {
  :root {
    --bg: #f5f6f8; --bg2: #ffffff; --bg3: #eceef2;
    --fg: #1c2028; --fg2: #5b6270; --border: #d8dbe2;
  }
}
* { box-sizing: border-box; margin: 0; padding: 0; }
body {
  background: var(--bg); color: var(--fg);
  font: 16px/1.7 -apple-system, "PingFang SC", "Microsoft YaHei", sans-serif;
  min-height: 100vh;
}
a { color: var(--accent); text-decoration: none; }

/* ── navbar ── */
nav {
  position: sticky; top: 0; z-index: 10;
  background: var(--bg2); border-bottom: 1px solid var(--border);
  display: flex; align-items: center; gap: 4px;
  padding: 0 12px; overflow-x: auto; white-space: nowrap;
}
nav .brand { font-weight: 700; margin-right: 10px; color: var(--fg); }
nav a.nav-item {
  color: var(--fg2); padding: 12px 10px; display: inline-block; font-size: 15px;
  border-bottom: 2px solid transparent;
}
nav a.nav-item.active { color: var(--accent); border-bottom-color: var(--accent); }
nav a.nav-item:active { opacity: .7; }

.wrap { max-width: 1000px; margin: 0 auto; padding: 20px 14px 60px; }

/* ── cards ── */
.card {
  background: var(--bg2); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 18px; margin-bottom: 16px;
}
.card h2 { font-size: 17px; margin-bottom: 10px; }
.stat-row { display: flex; gap: 12px; flex-wrap: wrap; }
.stat {
  flex: 1 1 100px; background: var(--bg3); border-radius: var(--radius);
  padding: 12px; text-align: center;
}
.stat .num { font-size: 26px; font-weight: 700; color: var(--accent); }
.stat .lbl { font-size: 13px; color: var(--fg2); }

/* ── paper grid ── */
.year-h { margin: 22px 0 8px; font-size: 15px; color: var(--fg2); }
.paper-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 10px; }
.paper-card {
  background: var(--bg2); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 14px; cursor: pointer; color: var(--fg); display: block;
}
.paper-card:hover { border-color: var(--accent); }
.paper-card .t { font-weight: 600; }
.paper-card .m { font-size: 13px; color: var(--fg2); margin-top: 4px; }
.paper-card .bar { height: 5px; background: var(--bg3); border-radius: 3px; margin-top: 10px; overflow: hidden; }
.paper-card .bar > i { display: block; height: 100%; background: var(--accent); }

/* ── buttons / inputs ── */
.btn {
  display: inline-block; background: var(--accent); color: #fff; border: 0;
  border-radius: 8px; padding: 10px 18px; font-size: 15px; cursor: pointer;
}
.btn.ghost { background: var(--bg3); color: var(--fg); border: 1px solid var(--border); }
.btn.danger { background: var(--red); }
.btn:disabled { opacity: .5; cursor: default; }
input[type=text], input[type=number], select, textarea {
  background: var(--bg3); border: 1px solid var(--border); color: var(--fg);
  border-radius: 8px; padding: 9px 12px; font-size: 15px; width: 100%;
}
textarea { font-family: inherit; }

/* ── practice ── */
.practice-layout { display: grid; grid-template-columns: 210px 1fr; gap: 16px; }
.qgrid {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(34px, 1fr));
  gap: 6px; align-content: start; max-height: 75vh; overflow-y: auto;
}
.qcell {
  aspect-ratio: 1; display: flex; align-items: center; justify-content: center;
  background: var(--bg3); border: 1px solid var(--border); border-radius: 7px;
  font-size: 13px; cursor: pointer; color: var(--fg2);
}
.qcell.cur { border-color: var(--accent); color: var(--accent); font-weight: 700; }
.qcell.right { background: color-mix(in srgb, var(--green) 22%, transparent); color: var(--green); }
.qcell.wrong { background: color-mix(in srgb, var(--red) 22%, transparent); color: var(--red); }
.qcell.picked { background: color-mix(in srgb, var(--accent) 25%, transparent); color: var(--accent); }

.qmeta { display: flex; justify-content: space-between; align-items: center; color: var(--fg2); font-size: 14px; margin-bottom: 10px; gap: 8px; }
.star { cursor: pointer; font-size: 20px; color: var(--fg2); background: none; border: none; }
.star.on { color: var(--amber); }
.qcontent { font-size: 17px; margin-bottom: 14px; white-space: pre-wrap; }
.qcontent img, .opt img, .qimg { max-width: 100%; height: auto; border-radius: 8px; margin: 8px 0; background: #fff; }
.qimg { display: block; cursor: zoom-in; }
.img-ph { color: var(--fg2); font-size: 14px; border: 1px dashed var(--border); border-radius: 8px; padding: 8px 12px; margin-bottom: 12px; }

.opt {
  display: flex; gap: 10px; align-items: flex-start;
  background: var(--bg3); border: 1px solid var(--border); border-radius: 8px;
  padding: 11px 14px; margin-bottom: 8px; cursor: pointer; width: 100%;
  color: var(--fg); font-size: 16px; text-align: left;
}
.opt:hover { border-color: var(--accent); }
.opt .lb { font-weight: 700; min-width: 20px; }
.opt.right { border-color: var(--green); background: color-mix(in srgb, var(--green) 14%, transparent); }
.opt.wrong { border-color: var(--red); background: color-mix(in srgb, var(--red) 14%, transparent); }
.opt.sel { border-color: var(--accent); background: color-mix(in srgb, var(--accent) 16%, transparent); }
.opt:disabled { cursor: default; opacity: 1; }

.explain {
  background: var(--bg3); border-left: 3px solid var(--accent); border-radius: 0 8px 8px 0;
  padding: 12px 14px; margin-top: 14px; font-size: 15px; white-space: pre-wrap;
}
.explain .ans { font-weight: 700; color: var(--green); }
.pager { display: flex; justify-content: space-between; margin-top: 18px; gap: 10px; }

/* toast */
#toast {
  position: fixed; bottom: 30px; left: 50%; transform: translateX(-50%);
  background: var(--bg3); border: 1px solid var(--border); color: var(--fg);
  padding: 10px 20px; border-radius: 20px; opacity: 0; transition: opacity .3s;
  pointer-events: none; z-index: 99; max-width: 90vw;
}
#toast.show { opacity: 1; }

/* ── exam ── */
.timer { font-variant-numeric: tabular-nums; font-weight: 700; color: var(--amber); }
.result-score { font-size: 44px; font-weight: 800; color: var(--accent); }
.review-item { border-bottom: 1px solid var(--border); padding: 10px 0; font-size: 15px; }
.review-item .ok { color: var(--green); } .review-item .no { color: var(--red); }

/* ── stats ── */
.hbar { display: flex; align-items: center; gap: 8px; margin: 6px 0; font-size: 14px; }
.hbar .name { width: 170px; color: var(--fg2); flex-shrink: 0; }
.hbar .track { flex: 1; background: var(--bg3); border-radius: 5px; height: 18px; overflow: hidden; }
.hbar .fill { height: 100%; background: var(--accent); border-radius: 5px; min-width: 2px; }
.hbar .val { width: 90px; text-align: right; font-variant-numeric: tabular-nums; }
.cal { display: grid; grid-template-columns: repeat(15, 1fr); gap: 4px; }
.cal .d { aspect-ratio: 1; border-radius: 4px; background: var(--bg3); position: relative; }
.cal .d.l1 { background: color-mix(in srgb, var(--accent) 25%, var(--bg3)); }
.cal .d.l2 { background: color-mix(in srgb, var(--accent) 55%, var(--bg3)); }
.cal .d.l3 { background: var(--accent); }

/* ── case / essay ── */
.tree a { display: block; padding: 7px 10px; border-radius: 7px; color: var(--fg2); font-size: 14px; }
.tree a.active, .tree a:hover { background: var(--bg3); color: var(--fg); }
.material { white-space: pre-wrap; font-size: 15.5px; }
.subq { border-top: 1px solid var(--border); padding: 14px 0; }
.subq .qt { font-weight: 600; margin-bottom: 8px; white-space: pre-wrap; }
details.refans { margin-top: 8px; }
details.refans summary { cursor: pointer; color: var(--accent); font-size: 14px; }
details.refans .body { background: var(--bg3); border-radius: 8px; padding: 10px 12px; margin-top: 8px; white-space: pre-wrap; font-size: 15px; }
.selfbtns { margin-top: 8px; display: flex; gap: 8px; }

/* ── admin ── */
table.list { width: 100%; border-collapse: collapse; font-size: 14px; }
table.list th, table.list td { border-bottom: 1px solid var(--border); padding: 8px 6px; text-align: left; vertical-align: top; }
table.list th { color: var(--fg2); font-weight: 600; }
.tag { display: inline-block; background: var(--bg3); border-radius: 5px; padding: 1px 8px; font-size: 12px; color: var(--fg2); }
.field { margin-bottom: 10px; }
.field label { display: block; font-size: 13px; color: var(--fg2); margin-bottom: 4px; }
.tabs { display: flex; gap: 6px; margin-bottom: 14px; flex-wrap: wrap; }
.tabs .btn { padding: 7px 14px; font-size: 14px; }

/* ── mobile ── */
@media (max-width: 720px) {
  .practice-layout { grid-template-columns: 1fr; }
  .qgrid {
    display: flex; overflow-x: auto; max-height: none; padding-bottom: 6px;
  }
  .qcell { min-width: 36px; aspect-ratio: 1; flex-shrink: 0; }
  .hbar .name { width: 108px; font-size: 12px; }
  .cal { grid-template-columns: repeat(10, 1fr); }
  .wrap { padding: 14px 10px 50px; }
  .opt { padding: 13px 14px; }
}