:root {
  --bg: #f6f3ea; --panel: #fffdf7; --ink: #1f2933; --muted: #66707b; --border: #ddd6c4;
  --accent: #c2410c; --accent-ink: #fff; --link: #1d5fbf; --good: #15803d; --soft: #efe9da;
  --cv-bg: #fffdf7; --cv-grid: rgba(60, 50, 30, .13); --cv-given: #1f2933; --cv-line: #2563eb; --cv-circle: #b45309;
  --cv-point: #4b5563; --cv-accent: #e11d48; --cv-good: #16a34a; --cv-label: #111827;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #14171c; --panel: #1c2027; --ink: #e7e9ee; --muted: #9aa3ad; --border: #343b47;
    --accent: #fb923c; --accent-ink: #1b1206; --link: #8cc4ff; --good: #4ade80; --soft: #232833;
    --cv-bg: #181c22; --cv-grid: rgba(255, 255, 255, .10); --cv-given: #e7e9ee; --cv-line: #60a5fa; --cv-circle: #fbbf24;
    --cv-point: #aab3bf; --cv-accent: #fb7185; --cv-good: #4ade80; --cv-label: #f3f4f6;
  }
}
* { box-sizing: border-box; }
html { background: var(--bg); }
body { margin: 0; color: var(--ink); background: var(--bg); font-family: "Hiragino Sans", "Noto Sans JP", "Yu Gothic", sans-serif; line-height: 1.8; }
a { color: var(--link); }
.wrap { max-width: 960px; margin: 0 auto; padding: 0 16px; }

.site-header { border-bottom: 1px solid var(--border); background: var(--panel); }
.site-header .wrap { display: flex; align-items: baseline; gap: 14px; padding-top: 12px; padding-bottom: 10px; flex-wrap: wrap; }
.site-name { margin: 0; font-size: 1.35rem; font-weight: 800; letter-spacing: .06em; }
.site-name a { color: var(--ink); text-decoration: none; }
.site-name a::before { content: "◎"; color: var(--accent); margin-right: 6px; }
.site-tag { margin: 0; color: var(--muted); font-size: .88rem; }

main.wrap { padding-top: 18px; padding-bottom: 40px; }
h1 { font-size: 1.6rem; line-height: 1.4; margin: .2em 0 .4em; }
h2 { font-size: 1.22rem; margin: 2em 0 .6em; padding-bottom: .25em; border-bottom: 2px solid var(--border); }
.crumbs { font-size: .85rem; color: var(--muted); }
.crumbs a { color: var(--muted); }
.lead { font-size: 1.05rem; }
.muted { color: var(--muted); }
.meta { display: flex; gap: 12px; flex-wrap: wrap; font-size: .9rem; color: var(--muted); margin: 0 0 12px; }
.stars { color: var(--accent); letter-spacing: .1em; }

.button, .sz-board button {
  font: inherit; font-size: .92rem; cursor: pointer; border-radius: 9px; border: 1px solid var(--border);
  background: var(--panel); color: var(--ink); padding: 6px 12px; text-decoration: none; display: inline-flex; align-items: center; gap: 6px; line-height: 1.4;
}
.button:hover, .sz-board button:hover { border-color: var(--accent); }
.button.primary, .sz-board button.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); font-weight: 700; }
.sz-board button:disabled { opacity: .45; cursor: default; }

/* 作図ボード */
.sz-board { background: var(--panel); border: 1px solid var(--border); border-radius: 14px; padding: 10px; margin: 14px 0; }
.sz-tools { display: flex; gap: 6px; flex-wrap: wrap; margin-bottom: 8px; }
.sz-tools button { padding: 6px 10px; }
.sz-tools button svg { width: 22px; height: 22px; fill: none; stroke: currentColor; stroke-width: 1.8; }
.sz-tools button svg .f { fill: currentColor; stroke: none; }
.sz-tools button.active { background: var(--ink); color: var(--panel); border-color: var(--ink); }
.sz-tools.dim { opacity: .4; pointer-events: none; }
.sz-canvas-wrap { position: relative; border-radius: 10px; overflow: hidden; border: 1px solid var(--border); }
.sz-canvas-wrap canvas { display: block; width: 100%; height: min(68vh, 560px, 118vw); min-height: 320px; touch-action: none; cursor: crosshair; }
.sz-zoom { position: absolute; right: 8px; top: 8px; display: flex; flex-direction: column; gap: 4px; }
.sz-zoom button { width: 34px; height: 34px; justify-content: center; padding: 0; font-size: 1.05rem; opacity: .9; }
.sz-caption { position: absolute; left: 8px; right: 8px; bottom: 8px; background: var(--panel); border: 1px solid var(--border); border-radius: 10px; padding: 8px 12px; font-size: .95rem; box-shadow: 0 4px 14px rgba(0,0,0,.12); }
.sz-status { display: flex; gap: 14px; flex-wrap: wrap; align-items: baseline; padding: 8px 2px 4px; font-size: .92rem; }
.sz-moves b { font-size: 1.05rem; }
.sz-msg { color: var(--muted); }
.sz-msg.warn { color: var(--accent); font-weight: 700; }
.sz-actions, .sz-demo-bar { display: flex; gap: 6px; flex-wrap: wrap; align-items: center; }
.sz-demo-count { min-width: 4.5em; text-align: center; font-weight: 700; }
.sz-hint { background: var(--soft); border-radius: 10px; padding: 10px 14px; margin: 10px 0 0; }
.sz-done { margin-top: 10px; border: 2px solid var(--good); border-radius: 12px; padding: 10px 14px; }
.sz-done p { margin: .3em 0; }
.sz-done-title { font-size: 1.25rem; font-weight: 800; color: var(--good); }
.sz-done-links { display: flex; gap: 8px; flex-wrap: wrap; }
[hidden] { display: none !important; }

/* 解説 */
.article ol.steps li { margin: .3em 0; }
.article p { margin: .7em 0; }
.box { background: var(--panel); border: 1px solid var(--border); border-radius: 12px; padding: 4px 18px; margin: 16px 0; }
.pager { display: flex; justify-content: space-between; gap: 10px; margin: 28px 0; flex-wrap: wrap; }
.ad-slot { min-height: 100px; margin: 22px 0; display: flex; align-items: center; justify-content: center; }
.ad-slot:empty { min-height: 0; margin: 0; }
#comments { min-height: 60px; }

/* 一覧 */
.hero { padding: 6px 0 4px; }
.hero h1 { font-size: 1.75rem; }
.levels h2 { display: flex; align-items: baseline; gap: 10px; }
.cards { list-style: none; padding: 0; margin: 12px 0; display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 14px; }
.cards a { display: block; height: 100%; background: var(--panel); border: 1px solid var(--border); border-radius: 12px; overflow: hidden; color: var(--ink); text-decoration: none; transition: transform .15s, border-color .15s; }
.cards a:hover { transform: translateY(-2px); border-color: var(--accent); }
.cards svg { display: block; width: 100%; height: auto; background: var(--cv-bg); border-bottom: 1px solid var(--border); }
.cards svg .g { stroke: var(--cv-given); fill: none; stroke-width: 2; vector-effect: non-scaling-stroke; }
.cards svg .gd { stroke: var(--cv-given); fill: none; stroke-width: 1; opacity: .35; stroke-dasharray: 3 4; vector-effect: non-scaling-stroke; }
.cards svg .a { stroke: var(--cv-good); fill: none; stroke-width: 3; vector-effect: non-scaling-stroke; }
.cards svg .s { stroke: var(--cv-point); fill: none; stroke-width: 1; opacity: .35; vector-effect: non-scaling-stroke; }
.cards svg .af { fill: var(--cv-good); opacity: .15; stroke: none; }
.cards svg .pt { fill: var(--cv-given); }
.cards svg .pa { fill: var(--cv-good); }
.cards svg text { fill: var(--cv-label); font: 600 13px sans-serif; }
.card-body { padding: 10px 14px 12px; }
.card-body h3 { margin: 0 0 4px; font-size: 1.05rem; }
.card-body p { margin: 0; font-size: .86rem; color: var(--muted); line-height: 1.6; }
.card-meta { display: flex; justify-content: space-between; font-size: .8rem; margin-top: 6px; }
.solved { color: var(--good); font-weight: 700; }

.site-footer { border-top: 1px solid var(--border); padding: 18px 0 28px; font-size: .88rem; color: var(--muted); }
.site-footer a { color: var(--muted); }
@media (max-width: 560px) {
  h1 { font-size: 1.35rem; }
  .sz-board { padding: 6px; margin-left: -8px; margin-right: -8px; }
  .sz-tools { flex-wrap: nowrap; gap: 4px; }
  .sz-tools button { flex: 1 1 0; flex-direction: column; gap: 0; padding: 4px 2px; justify-content: center; }
  .sz-tools button span { font-size: .74rem; white-space: nowrap; }
  .site-tag { font-size: .8rem; }
}