:root {
  --bg: #f6f7f9; --card: #ffffff; --text: #1c2430; --muted: #667085; --line: #e2e6ec;
  --accent: #1f5fd1; --accent-ink: #ffffff; --good: #137a3f; --good-bg: #e3f5ea;
  --warn: #a15c00; --warn-bg: #fdf0d9; --bad: #b42318; --bad-bg: #fde8e6; --code: #eef1f5;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #12161c; --card: #1a2029; --text: #e6eaf0; --muted: #96a0b0; --line: #2c3541;
    --accent: #6ea0ff; --accent-ink: #0b1220; --good: #5fd08b; --good-bg: #17301f;
    --warn: #f0b45a; --warn-bg: #36280f; --bad: #ff8a80; --bad-bg: #3a1b18; --code: #232b36;
  }
}
* { box-sizing: border-box; }
body { margin: 0; background: var(--bg); color: var(--text);
  font: 16px/1.55 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif; }
a { color: var(--accent); }
.wrap { max-width: 980px; margin: 0 auto; padding: 0 16px; }
main.wrap { padding-top: 20px; padding-bottom: 60px; }
h1 { font-size: 1.7rem; margin: .3em 0 .6em; }
h2 { font-size: 1.2rem; margin: 1.6em 0 .5em; }
h3 { margin: 0 0 .2em; }
.muted { color: var(--muted); } .small { font-size: .88rem; }
.pre { white-space: pre-wrap; }
.right { text-align: right; }
code { background: var(--code); padding: .1em .35em; border-radius: 4px; font-size: .9em; }

.top { background: var(--card); border-bottom: 1px solid var(--line); }
.bar { display: flex; align-items: center; gap: 18px; flex-wrap: wrap; padding-top: 10px; padding-bottom: 10px; }
.brand { font-weight: 700; text-decoration: none; color: var(--text); font-size: 1.1rem; }
nav { display: flex; gap: 4px; flex-wrap: wrap; flex: 1; align-items: center; }
nav a { text-decoration: none; color: var(--muted); padding: 6px 10px; border-radius: 6px; }
nav a:hover { background: var(--code); } nav a.on { color: var(--text); background: var(--code); font-weight: 600; }
nav .sep { width: 1px; height: 20px; background: var(--line); margin: 0 6px; }
.who { display: flex; gap: 12px; align-items: center; font-size: .92rem; }
.who form { margin: 0; }

button.link { background: none; border: 0; padding: 0; color: var(--accent); cursor: pointer; font: inherit; }
button.danger { color: var(--bad); }
.btn { display: inline-block; background: var(--accent); color: var(--accent-ink); border: 1px solid var(--accent);
  padding: 9px 18px; border-radius: 8px; font: inherit; font-weight: 600; cursor: pointer; text-decoration: none; }
.btn:hover { filter: brightness(1.08); } .btn:disabled { opacity: .6; cursor: default; }
.btn.ghost { background: transparent; color: var(--accent); }

.card { background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 18px 20px; margin: 0 0 16px; }
.card h2:first-child { margin-top: 0; }
.card.narrow { max-width: 440px; margin: 30px auto; }
.flash { padding: 10px 14px; border-radius: 8px; margin-bottom: 14px; border: 1px solid; }
.flash.ok { background: var(--good-bg); color: var(--good); border-color: var(--good); }
.flash.error { background: var(--bad-bg); color: var(--bad); border-color: var(--bad); }

label { display: block; font-weight: 600; font-size: .92rem; }
label small { display: block; font-weight: 400; color: var(--muted); }
input:not([type=radio]):not([type=file]), select, textarea { display: block; width: 100%; margin-top: 4px; padding: 9px 11px;
  border: 1px solid var(--line); border-radius: 8px; background: var(--bg); color: var(--text); font: inherit; }
input:focus, select:focus, textarea:focus { outline: 2px solid var(--accent); outline-offset: 1px; }
.stack { display: grid; gap: 14px; }
.inline-form { display: flex; gap: 12px; align-items: flex-end; flex-wrap: wrap; }
.inline-form label { flex: 1; min-width: 200px; }

.grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(190px, 1fr)); gap: 14px; margin-bottom: 8px; }
.tile { background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 16px 18px;
  display: flex; flex-direction: column; gap: 2px; text-decoration: none; color: var(--text); }
.tile strong { font-size: 1.35rem; } .tile span { color: var(--muted); font-size: .9rem; }
a.tile:hover { border-color: var(--accent); }

.list { display: grid; gap: 10px; }
.row { display: flex; justify-content: space-between; align-items: center; gap: 12px; background: var(--card);
  border: 1px solid var(--line); border-radius: 10px; padding: 14px 18px; text-decoration: none; color: var(--text); }
a.row:hover { border-color: var(--accent); }
.pill { display: inline-block; padding: 2px 10px; border-radius: 99px; font-size: .85rem; background: var(--code); color: var(--muted); }
.pill.good, td.good { background: var(--good-bg); color: var(--good); }
.pill.warn, td.warn { background: var(--warn-bg); color: var(--warn); }
.toc-list { padding-left: 1.4em; } .toc-list li { margin: .4em 0; font-size: 1.05rem; }

table { width: 100%; border-collapse: collapse; background: var(--card); border: 1px solid var(--line); border-radius: 10px; overflow: hidden; }
th, td { padding: 9px 12px; text-align: left; border-bottom: 1px solid var(--line); font-size: .95rem; }
th { background: var(--code); font-size: .85rem; }
tr:last-child td { border-bottom: 0; }
td form { margin: 0; display: inline; }
.scroll { overflow-x: auto; } th.qcol { max-width: 120px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.ann { display: flex; justify-content: space-between; gap: 10px; padding: 8px 0; border-top: 1px solid var(--line); margin-top: 8px; }
.ann form { margin: 0; }

.prose { background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 8px 28px 24px; overflow-wrap: break-word; }
.prose img { max-width: 100%; height: auto; }
.prose pre, pre.code { background: var(--code); padding: 14px; border-radius: 8px; overflow-x: auto; font-size: .9rem; line-height: 1.45; }
.prose table { margin: 1em 0; }
.prose blockquote { margin: 1em 0; padding: .1em 1em; border-left: 4px solid var(--accent); color: var(--muted); }
.pager { display: flex; justify-content: space-between; gap: 10px; margin-top: 18px; }

.qcard { background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 16px 20px; margin: 0 0 16px; min-width: 0; }
.qcard.right-answer { border-color: var(--good); } .qcard.wrong-answer { border-color: var(--bad); }
.qnum { color: var(--muted); font-size: .85rem; font-weight: 600; padding: 0 6px; }
.qtext { font-size: 1.05rem; margin: .2em 0 .8em; }
.choices { display: grid; gap: 8px; }
.choice { display: flex; gap: 10px; align-items: flex-start; font-weight: 400; font-size: 1rem; padding: 9px 12px;
  border: 1px solid var(--line); border-radius: 8px; cursor: pointer; }
.choice:hover { border-color: var(--accent); }
.choice input { margin-top: .3em; }
.choice.is-answer { background: var(--good-bg); border-color: var(--good); }
.choice.is-wrong { background: var(--bad-bg); border-color: var(--bad); }
.feedback:not(:empty) { margin-top: 12px; padding-top: 10px; border-top: 1px solid var(--line); }
.submitbar { display: flex; align-items: center; gap: 14px; }
.summary { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; font-size: 1.15rem; }

@media (max-width: 600px) { .prose { padding: 4px 16px 18px; } .bar { gap: 8px; } }

label.check { display: flex; gap: 8px; align-items: center; font-weight: 400; }
label.check input { width: auto; margin: 0; }
.warn-text { color: var(--warn); }
textarea { resize: vertical; }