:root {
  --bg: #f1f5f9;
  --surface: #ffffff;
  --surface-2: #f8fafc;
  --text: #0f172a;
  --muted: #64748b;
  --border: #e2e8f0;
  --accent: #0284c7;
  --accent-ink: #ffffff;
  --accent-soft: #e0f2fe;
  --ok: #16a34a;
  --ok-soft: #dcfce7;
  --ng: #dc2626;
  --ng-soft: #fee2e2;
  --warn: #d97706;
  --warn-soft: #fef3c7;
  --shadow: 0 1px 2px rgba(15, 23, 42, .06), 0 4px 16px rgba(15, 23, 42, .06);
  --radius: 14px;
  --d1: #0ea5e9; --d2: #ef4444; --d3: #8b5cf6; --d4: #f59e0b; --d5: #10b981;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0b1220;
    --surface: #111a2e;
    --surface-2: #162038;
    --text: #e2e8f0;
    --muted: #94a3b8;
    --border: #243049;
    --accent: #38bdf8;
    --accent-ink: #06121f;
    --accent-soft: #0c2a40;
    --ok: #4ade80; --ok-soft: #0f2e1c;
    --ng: #f87171; --ng-soft: #3b1414;
    --warn: #fbbf24; --warn-soft: #3a2a07;
    --shadow: 0 1px 2px rgba(0,0,0,.4), 0 6px 20px rgba(0,0,0,.35);
  }
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  font-family: "Segoe UI", "Hiragino Sans", "Hiragino Kaku Gothic ProN", "Noto Sans JP", "Yu Gothic UI", Meiryo, system-ui, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.65;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}
a { color: var(--accent); }
button { font: inherit; }
[hidden] { display: none !important; }

.topbar {
  position: sticky; top: 0; z-index: 10;
  display: flex; align-items: center; justify-content: space-between; gap: 12px;
  padding: 10px 16px;
  background: color-mix(in srgb, var(--surface) 88%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}
.brand { display: flex; align-items: center; gap: 10px; text-decoration: none; color: var(--text); font-weight: 700; }
.brand-mark {
  display: inline-grid; place-items: center;
  width: 34px; height: 34px; border-radius: 9px;
  background: #0f172a; color: #38bdf8; font-size: 14px; letter-spacing: .5px;
}
.brand-text small { font-weight: 500; color: var(--muted); margin-left: 6px; }

.container { width: 100%; max-width: 820px; margin: 0 auto; padding: 20px 16px 48px; flex: 1; }
.footer { padding: 16px; text-align: center; color: var(--muted); font-size: 12px; border-top: 1px solid var(--border); }
.footer p { margin: 0; max-width: 820px; margin-inline: auto; }
.loading { color: var(--muted); text-align: center; padding: 48px 0; }

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 20px;
  margin-bottom: 16px;
}
h1 { font-size: 1.45rem; margin: 0 0 6px; }
h2 { font-size: 1.1rem; margin: 0 0 12px; }
.lead { color: var(--muted); margin: 0 0 16px; }

.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  padding: 10px 18px; border-radius: 10px;
  border: 1px solid var(--accent); background: var(--accent); color: var(--accent-ink);
  font-weight: 600; cursor: pointer; text-decoration: none;
  transition: transform .05s ease, filter .15s ease;
}
.btn:hover { filter: brightness(1.06); }
.btn:active { transform: translateY(1px); }
.btn:disabled { opacity: .5; cursor: not-allowed; }
.btn.ghost { background: transparent; color: var(--text); border-color: var(--border); }
.btn.ghost:hover { background: var(--surface-2); }
.btn.small { padding: 6px 12px; font-size: .9rem; }
.btn.block { width: 100%; }
.btn.danger { background: var(--ng); border-color: var(--ng); color: #fff; }
.btn-row { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 16px; }

/* home */
.hero { display: grid; gap: 14px; }
.stat-row { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; }
.stat {
  background: var(--surface-2); border: 1px solid var(--border); border-radius: 12px;
  padding: 12px; text-align: center;
}
.stat b { display: block; font-size: 1.4rem; line-height: 1.2; }
.stat span { color: var(--muted); font-size: .8rem; }

.domain-list { display: grid; gap: 10px; }
.domain {
  display: grid; grid-template-columns: auto 1fr auto; align-items: center; gap: 12px;
  padding: 12px 14px; border: 1px solid var(--border); border-radius: 12px;
  background: var(--surface-2); cursor: pointer; text-align: left; color: var(--text);
}
.domain:hover { border-color: var(--accent); }
.domain.selected { border-color: var(--accent); background: var(--accent-soft); }
.dnum {
  width: 36px; height: 36px; border-radius: 10px; display: grid; place-items: center;
  color: #fff; font-weight: 700;
}
.dnum[data-d="1"] { background: var(--d1); }
.dnum[data-d="2"] { background: var(--d2); }
.dnum[data-d="3"] { background: var(--d3); }
.dnum[data-d="4"] { background: var(--d4); }
.dnum[data-d="5"] { background: var(--d5); }
.dname { font-weight: 600; }
.dsub { color: var(--muted); font-size: .8rem; }
.dacc { text-align: right; font-size: .85rem; color: var(--muted); white-space: nowrap; }
.dacc b { display: block; font-size: 1.05rem; color: var(--text); }
.bar { height: 6px; border-radius: 99px; background: var(--border); overflow: hidden; margin-top: 6px; }
.bar i { display: block; height: 100%; background: var(--ok); }

.opts { display: grid; grid-template-columns: repeat(auto-fit, minmax(180px, 1fr)); gap: 10px; margin-top: 8px; }
.opt { display: grid; gap: 6px; }
.opt label { font-size: .85rem; color: var(--muted); }
.seg { display: flex; border: 1px solid var(--border); border-radius: 10px; overflow: hidden; background: var(--surface-2); }
.seg button {
  flex: 1; padding: 8px 4px; border: 0; background: transparent; color: var(--text); cursor: pointer; font-weight: 600;
}
.seg button + button { border-left: 1px solid var(--border); }
.seg button.on { background: var(--accent); color: var(--accent-ink); }

.mode-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 12px; }
.mode {
  display: grid; gap: 6px; padding: 16px; border-radius: 12px; cursor: pointer; text-align: left;
  border: 1px solid var(--border); background: var(--surface-2); color: var(--text);
}
.mode:hover { border-color: var(--accent); }
.mode h3 { margin: 0; font-size: 1rem; }
.mode p { margin: 0; color: var(--muted); font-size: .85rem; }
.mode .tag { font-size: .75rem; color: var(--accent); font-weight: 700; }

/* quiz */
.qhead { display: flex; align-items: center; justify-content: space-between; gap: 10px; flex-wrap: wrap; margin-bottom: 10px; }
.qmeta { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; font-size: .85rem; color: var(--muted); }
.badge { display: inline-block; padding: 2px 9px; border-radius: 99px; font-size: .75rem; font-weight: 700; color: #fff; }
.badge[data-d="1"] { background: var(--d1); }
.badge[data-d="2"] { background: var(--d2); }
.badge[data-d="3"] { background: var(--d3); }
.badge[data-d="4"] { background: var(--d4); }
.badge[data-d="5"] { background: var(--d5); }
.timer { font-variant-numeric: tabular-nums; font-weight: 700; }
.timer.low { color: var(--ng); }
.progress { height: 6px; background: var(--border); border-radius: 99px; overflow: hidden; margin-bottom: 18px; }
.progress i { display: block; height: 100%; background: var(--accent); transition: width .2s ease; }
.qtext { font-size: 1.05rem; font-weight: 600; margin: 0 0 16px; white-space: pre-wrap; }

.choices { display: grid; gap: 10px; }
.choice {
  display: grid; grid-template-columns: 32px 1fr; align-items: start; gap: 10px;
  width: 100%; padding: 12px 14px; border-radius: 12px; text-align: left;
  border: 1px solid var(--border); background: var(--surface-2); color: var(--text); cursor: pointer;
  line-height: 1.55;
}
.choice:hover:not(:disabled) { border-color: var(--accent); }
.choice .k {
  width: 28px; height: 28px; border-radius: 8px; display: grid; place-items: center;
  background: var(--surface); border: 1px solid var(--border); font-weight: 700; font-size: .85rem;
}
.choice.picked { border-color: var(--accent); background: var(--accent-soft); }
.choice.picked .k { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }
.choice.correct { border-color: var(--ok); background: var(--ok-soft); }
.choice.correct .k { background: var(--ok); color: #fff; border-color: var(--ok); }
.choice.wrong { border-color: var(--ng); background: var(--ng-soft); }
.choice.wrong .k { background: var(--ng); color: #fff; border-color: var(--ng); }
.choice:disabled { cursor: default; }

.explain {
  margin-top: 16px; padding: 14px 16px; border-radius: 12px;
  border-left: 4px solid var(--accent); background: var(--surface-2);
}
.explain.ok { border-left-color: var(--ok); }
.explain.ng { border-left-color: var(--ng); }
.explain .verdict { font-weight: 700; margin: 0 0 6px; }
.explain.ok .verdict { color: var(--ok); }
.explain.ng .verdict { color: var(--ng); }
.explain p { margin: 0; }

.qnav { display: flex; justify-content: space-between; align-items: center; gap: 10px; margin-top: 18px; flex-wrap: wrap; }
.qnav .spacer { flex: 1; }
.flag { color: var(--warn); border-color: var(--warn); }
.flag.on { background: var(--warn-soft); }

.navgrid { display: grid; grid-template-columns: repeat(auto-fill, minmax(38px, 1fr)); gap: 6px; margin-top: 12px; }
.navgrid button {
  padding: 6px 0; border-radius: 8px; border: 1px solid var(--border); background: var(--surface-2);
  color: var(--text); cursor: pointer; font-size: .8rem;
}
.navgrid button.done { background: var(--accent-soft); border-color: var(--accent); }
.navgrid button.flagged { box-shadow: inset 0 0 0 2px var(--warn); }
.navgrid button.cur { outline: 2px solid var(--accent); }

/* result */
.score-wrap { display: grid; grid-template-columns: auto 1fr; gap: 20px; align-items: center; }
.ring { width: 120px; height: 120px; }
.ring text { font-weight: 700; font-size: 22px; fill: var(--text); }
.pass { font-weight: 700; }
.pass.ok { color: var(--ok); }
.pass.ng { color: var(--ng); }
.table { width: 100%; border-collapse: collapse; font-size: .9rem; }
.table th, .table td { padding: 8px 6px; border-bottom: 1px solid var(--border); text-align: left; }
.table th { color: var(--muted); font-weight: 600; font-size: .8rem; }
.table td.num { text-align: right; font-variant-numeric: tabular-nums; }

.review { display: grid; gap: 12px; }
.review details { border: 1px solid var(--border); border-radius: 12px; background: var(--surface-2); }
.review summary { padding: 12px 14px; cursor: pointer; font-weight: 600; list-style: none; display: flex; gap: 8px; align-items: flex-start; }
.review summary::-webkit-details-marker { display: none; }
.review summary .mark { flex: none; font-weight: 700; }
.review summary .mark.ok { color: var(--ok); }
.review summary .mark.ng { color: var(--ng); }
.review .body { padding: 0 14px 14px; }
.review .body p { margin: 6px 0; }
.ans-ok { color: var(--ok); font-weight: 600; }
.ans-ng { color: var(--ng); font-weight: 600; text-decoration: line-through; }

.history li { display: flex; justify-content: space-between; gap: 8px; padding: 6px 0; border-bottom: 1px solid var(--border); font-size: .9rem; }
.history { list-style: none; padding: 0; margin: 0; }
.history .when { color: var(--muted); }

.kbd { display: inline-block; padding: 0 6px; border: 1px solid var(--border); border-bottom-width: 2px; border-radius: 5px; font-size: .75rem; background: var(--surface-2); }
.hint { color: var(--muted); font-size: .8rem; margin-top: 10px; }

@media (max-width: 520px) {
  .stat-row { grid-template-columns: repeat(3, 1fr); }
  .stat b { font-size: 1.15rem; }
  .score-wrap { grid-template-columns: 1fr; justify-items: center; text-align: center; }
  .domain { grid-template-columns: auto 1fr; }
  .dacc { grid-column: 2; text-align: left; }
  .dacc b { display: inline; margin-right: 6px; }
  .hint { display: none; }
}

/* ===== figures (inline SVG) ===== */
.fig { width: 100%; height: auto; display: block; font-family: inherit; }
.fig .box { fill: var(--surface-2); stroke: var(--border); stroke-width: 1.5; }
.fig .box-accent { fill: var(--accent); stroke: var(--accent); stroke-width: 1.5; }
.fig .box-ok { fill: var(--ok-soft); stroke: var(--ok); stroke-width: 1.5; }
.fig .box-ng { fill: var(--ng-soft); stroke: var(--ng); stroke-width: 1.5; }
.fig .box-warn { fill: var(--warn-soft); stroke: var(--warn); stroke-width: 1.5; }
.fig .line { fill: none; stroke: var(--muted); stroke-width: 2; }
.fig .fill { fill: var(--accent); stroke: none; }
.fig .t { fill: var(--text); stroke: none; }
.fig .t-muted { fill: var(--muted); stroke: none; }
.fig .t-inv { fill: #ffffff; stroke: none; }
.fig .t-b { font-weight: 700; }
.figure { margin: 18px 0; padding: 14px; border: 1px solid var(--border); border-radius: 12px; background: var(--surface); }
.figure figcaption { margin-top: 8px; font-size: .85rem; color: var(--muted); text-align: center; }
.explain .figure { margin: 12px 0 0; background: var(--surface); }
.explain .learn-link { display: inline-block; margin-top: 10px; font-size: .9rem; font-weight: 600; }

/* ===== learn pages ===== */
.learn-layout { display: grid; grid-template-columns: 240px 1fr; gap: 20px; max-width: 1080px; margin: 0 auto; padding: 20px 16px 48px; width: 100%; }
.toc { position: sticky; top: 64px; align-self: start; max-height: calc(100vh - 80px); overflow: auto; font-size: .88rem; }
.toc h3 { margin: 0 0 8px; font-size: .8rem; color: var(--muted); text-transform: uppercase; letter-spacing: .05em; }
.toc ol { list-style: none; padding: 0; margin: 0 0 16px; }
.toc li { margin: 2px 0; }
.toc a { display: block; padding: 6px 10px; border-radius: 8px; color: var(--text); text-decoration: none; }
.toc a:hover { background: var(--surface-2); }
.toc a.cur { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.toc a.done::before { content: "✓ "; color: var(--ok); }
.lesson { scroll-margin-top: 70px; }
.lesson-head { display: flex; align-items: baseline; gap: 10px; flex-wrap: wrap; margin-bottom: 4px; }
.lesson-head .obj { font-weight: 700; color: var(--accent); }
.lesson-head .min { color: var(--muted); font-size: .85rem; }
.lesson h2 { font-size: 1.35rem; margin: 0 0 12px; }
.lesson h3 { font-size: 1.05rem; margin: 22px 0 8px; padding-left: 10px; border-left: 4px solid var(--accent); }
.lesson p { margin: 0 0 12px; }
.lesson ul { margin: 0 0 12px; padding-left: 1.3em; }
.lesson li { margin: 4px 0; }
.callout { padding: 12px 16px; border-radius: 12px; margin: 14px 0; border-left: 4px solid; }
.callout b { display: block; margin-bottom: 4px; font-size: .85rem; }
.callout.tip { background: var(--warn-soft); border-color: var(--warn); }
.callout.example { background: var(--accent-soft); border-color: var(--accent); }
.terms { display: grid; gap: 8px; margin: 12px 0; }
.term { display: grid; grid-template-columns: minmax(120px, 34%) 1fr; gap: 10px; padding: 10px 12px; border: 1px solid var(--border); border-radius: 10px; background: var(--surface-2); font-size: .92rem; }
.term .tn { font-weight: 700; }
.term .te { display: block; color: var(--muted); font-size: .8rem; font-weight: 400; }
.compare { width: 100%; border-collapse: collapse; font-size: .9rem; margin: 12px 0; }
.compare th, .compare td { padding: 8px 10px; border: 1px solid var(--border); text-align: left; vertical-align: top; }
.compare th { background: var(--surface-2); font-weight: 700; }
.lesson-foot { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; margin-top: 20px; padding-top: 16px; border-top: 1px solid var(--border); }
.domain-nav { display: flex; justify-content: space-between; gap: 10px; flex-wrap: wrap; margin-top: 8px; }
.path { display: grid; gap: 10px; counter-reset: step; }
.step { display: grid; grid-template-columns: 36px 1fr; gap: 12px; align-items: start; padding: 12px 14px; border: 1px solid var(--border); border-radius: 12px; background: var(--surface-2); }
.step::before { counter-increment: step; content: counter(step); width: 32px; height: 32px; border-radius: 50%; display: grid; place-items: center; background: var(--accent); color: var(--accent-ink); font-weight: 700; }
.step b { display: block; }
.step span { color: var(--muted); font-size: .9rem; }
.lesson-cards { display: grid; gap: 10px; }
.lesson-card { display: grid; grid-template-columns: auto 1fr auto; gap: 12px; align-items: center; padding: 12px 14px; border: 1px solid var(--border); border-radius: 12px; background: var(--surface-2); color: var(--text); text-decoration: none; }
.lesson-card:hover { border-color: var(--accent); }
.lesson-card .obj { font-weight: 700; color: var(--accent); min-width: 2.6em; }
.lesson-card .sum { color: var(--muted); font-size: .85rem; display: block; }
.lesson-card .st { font-size: .8rem; color: var(--muted); white-space: nowrap; }
.lesson-card.done .st { color: var(--ok); font-weight: 700; }
.chk { display: inline-flex; align-items: center; gap: 8px; cursor: pointer; user-select: none; }
.chk input { width: 18px; height: 18px; accent-color: var(--ok); }
@media (max-width: 760px) {
  .learn-layout { grid-template-columns: 1fr; }
  .toc { position: static; max-height: none; }
  .toc ol { display: flex; flex-wrap: wrap; gap: 6px; }
  .toc a { border: 1px solid var(--border); padding: 4px 10px; }
  .term { grid-template-columns: 1fr; gap: 2px; }
}