:root{--accent:#e0663a;--bg:#fbf8f1;--ink:#2b2a33;--mute:#7a7684;--card:#fff;--line:#e6e0d2}
*{box-sizing:border-box}
body{margin:0;background:var(--bg);color:var(--ink);font-family:"Zen Maru Gothic",system-ui,sans-serif;line-height:1.85;font-size:16px}
.serif{font-family:"Shippori Mincho",serif}
.wrap{max-width:860px;margin:0 auto;padding:0 16px}
a{color:#1b6ca8}
.top{padding:36px 0 14px}.kick{color:var(--mute);font-size:14px}
h1{font-size:clamp(30px,6vw,46px);margin:.1em 0;line-height:1.25}h1 em{font-style:normal;color:var(--accent)}
.top p{max-width:34em;margin:.4em 0}
.stats{margin-top:8px;color:var(--mute);font-size:14px}.stats b{color:var(--accent);font-size:18px}
.nav{display:flex;flex-wrap:wrap;gap:8px;margin:12px 0}
.navb{background:#fff;border:2px solid var(--line);border-radius:999px;padding:6px 14px;text-decoration:none;color:var(--ink);font-weight:700;font-size:14px}
.navb:hover{border-color:var(--accent)}
.bar{display:flex;flex-wrap:wrap;gap:6px;margin:8px 0;align-items:center}
.chip,.tbtn{font:inherit;font-size:14px;border:2px solid var(--line);background:#fff;color:var(--ink);border-radius:999px;padding:3px 12px;cursor:pointer}
.chip.on,.tbtn.on{background:var(--accent);border-color:var(--accent);color:#fff}
.tbtn{border-radius:10px;padding:6px 14px;font-weight:700}
.scenes{display:grid;grid-template-columns:repeat(auto-fill,minmax(104px,1fr));gap:8px;margin:12px 0}
.scene{border:2px solid var(--line);background:#fff;border-radius:14px;padding:8px 4px;text-align:center;cursor:pointer;font:inherit;font-size:13px;font-weight:700}
.scene span{display:block;font-size:26px;line-height:1.2}.scene.on{border-color:var(--accent);background:#fff1ea}
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(250px,1fr));gap:14px;margin:14px 0}
.card{position:relative;display:block;background:var(--card);border-radius:16px;overflow:hidden;text-decoration:none;color:var(--ink);box-shadow:0 2px 0 var(--line),0 6px 16px rgba(0,0,0,.05);transition:transform .15s}
a.card:hover{transform:translateY(-3px)}
.card .band{background:var(--accent);color:#fff;font-size:12px;font-weight:700;padding:3px 12px;display:flex;justify-content:space-between}
.card .body{padding:10px 14px 14px}.card h3{margin:.1em 0 .2em;font-size:19px;line-height:1.4}
.qq{color:var(--mute);font-size:14px;line-height:1.6}
.card.stub{opacity:.5}.stamp{position:absolute;right:8px;bottom:8px;border:2px solid #23804f;color:#23804f;border-radius:8px;font-size:12px;padding:0 6px;transform:rotate(-6deg);font-weight:700;background:#fff}
.hero{background:linear-gradient(135deg,var(--accent),color-mix(in srgb,var(--accent) 60%,#fff));color:#fff;padding:26px 0 22px}
.hero .meta{display:flex;gap:8px;flex-wrap:wrap;font-size:13px;font-weight:700}.hero .meta span{background:rgba(255,255,255,.22);border-radius:999px;padding:1px 10px}
.hero h1{font-size:clamp(26px,5vw,38px)}.hero .q{font-size:19px;font-weight:700;margin-top:6px}
.back{display:inline-block;margin:12px 0 0;font-size:14px}
.sec{margin:30px 0}.sec h2{font-size:25px;margin:0 0 10px;padding-left:12px;border-left:6px solid var(--accent)}
.panel{background:#fff;border-radius:14px;padding:14px 16px;box-shadow:0 2px 0 var(--line)}
.note-box{background:#fff8dc;border-radius:10px;padding:8px 12px;font-size:14px;margin:8px 0}
.step{display:flex;gap:12px;margin:14px 0}.step .n{flex:none;width:34px;height:34px;border-radius:50%;background:var(--accent);color:#fff;font-weight:700;display:flex;align-items:center;justify-content:center}
.step>div:last-child{min-width:0}.step h3{margin:0 0 2px;font-size:19px}.step p{margin:.2em 0}
.math{background:#f3efe6;border-radius:10px;padding:8px 14px;margin:6px 0;font-size:18px;font-family:"Zen Maru Gothic",monospace;overflow-x:auto;white-space:pre}
.one{background:var(--ink);color:#fff;border-radius:16px;padding:14px 18px;font-size:20px;font-weight:700;margin:26px 0}.one small{display:block;color:#ffd9a8;font-size:12px}
.opt{display:block;width:100%;text-align:left;font:inherit;background:#fff;border:2px solid var(--line);border-radius:12px;padding:8px 14px;margin:6px 0;cursor:pointer}
.opt:hover:not(:disabled){border-color:var(--accent)}.opt.ok{border-color:#23804f;background:#e7f6ec}.opt.ng{border-color:#c0453a;background:#fdeceb}
.why{display:none;margin-top:6px;font-size:14px;color:#444}.why.show{display:block}
.result{font-weight:700;margin:8px 0}
.pit{background:#fff;border-radius:12px;padding:10px 14px;margin:8px 0;border-left:5px solid #c0453a}.pit .bad{color:#c0453a;font-weight:700}.pit .good{color:#23804f;font-weight:700}
details{background:#fff;border-radius:10px;padding:6px 14px;margin:6px 0}summary{cursor:pointer;font-weight:700}
.badge{background:rgba(255,255,255,.35)}
.prac{background:#fff;border-radius:12px;padding:12px 16px;margin:10px 0}
.prac .ans{display:none;margin-top:8px;border-top:1px dashed var(--line);padding-top:8px}.prac .ans.show{display:block}
footer{text-align:center;color:var(--mute);font-size:13px;padding:40px 0}
/* widgets */
.wg{background:#fff;border:2px solid var(--line);border-radius:16px;padding:14px 16px;margin:8px 0}
.wg label{display:block;font-size:14px;font-weight:700;margin-top:8px}
.wg input[type=range]{width:100%;accent-color:var(--accent)}
.wg .out{font-size:20px;font-weight:700;margin:6px 0}.wg .out b{color:var(--accent)}
.wg svg{max-width:100%;height:auto;display:block}
.wg input[type=number]{font:inherit;width:6em;padding:3px 6px;border:2px solid var(--line);border-radius:8px}
.wg-hint{font-size:13px;color:var(--mute)}
.tree{max-width:100%;position:relative;overflow-x:auto;background:#fff;border-radius:14px;padding:10px}
.tree svg{position:absolute;left:0;top:0;pointer-events:none}
.tnode{position:absolute;width:150px;font:inherit;font-size:12.5px;line-height:1.35;text-align:left;border:2px solid var(--accent);background:#fff;border-radius:10px;padding:5px 8px;cursor:pointer}
.tnode.stub{border-style:dashed;opacity:.55}.tnode.dim{opacity:.18}.tnode.sel{background:var(--accent);color:#fff}
.legend{font-size:13px;color:var(--mute)}
ruby rt{font-size:.5em}
@media(max-width:600px){body{font-size:15px}.hero .q{font-size:17px}}
/* ===== 見た目の作り直し（方眼ノート＋黒板） ===== */
body{background-color:#fbf8f1;background-image:linear-gradient(rgba(60,110,160,.09) 1px,transparent 1px),linear-gradient(90deg,rgba(60,110,160,.09) 1px,transparent 1px);background-size:24px 24px}
.ic{width:1.15em;height:1.15em;vertical-align:-.2em;flex:none}
.scene span .ic{width:30px;height:30px;vertical-align:0}.scene span{color:var(--accent);font-size:0;line-height:1}
.scene{color:var(--ink);white-space:nowrap}.scene.on span{color:var(--accent)}
.navb{display:inline-flex;align-items:center;gap:6px}.navb .ic{color:var(--accent)}
.chip .ic{width:1em;height:1em;vertical-align:-.15em}
.band .ic{width:1.1em;height:1.1em;vertical-align:-.2em;margin-right:2px}
.hero .meta .ic{width:1.1em;height:1.1em;vertical-align:-.2em}
.thumb{background-color:color-mix(in srgb,var(--accent) 7%,#fffdf6);background-image:linear-gradient(color-mix(in srgb,var(--accent) 16%,transparent) 1px,transparent 1px),linear-gradient(90deg,color-mix(in srgb,var(--accent) 16%,transparent) 1px,transparent 1px);background-size:16px 16px;color:var(--accent);height:118px;display:flex;align-items:center;justify-content:center;border-bottom:2px dashed color-mix(in srgb,var(--accent) 35%,#fff)}
.thumb .th{width:92%;height:100%;padding:8px 0}
.thumb .th-ic{display:flex;align-items:center;justify-content:center;opacity:.55}.thumb .th-ic .ic{width:52px;height:52px}
.card{border:2px solid var(--ink);box-shadow:3px 4px 0 var(--ink);border-radius:14px}
a.card:hover{transform:translate(-2px,-2px);box-shadow:5px 6px 0 var(--ink)}
.card.stub{opacity:.62}.card.stub .thumb{filter:grayscale(.5)}
.card .band{font-size:13px}
.top{padding:0}
.stage{background:#24403a;border-bottom:10px solid #b78a54;box-shadow:inset 0 0 90px rgba(0,0,0,.35);color:#f3f1e6;padding:34px 0 30px;margin-bottom:6px;background-image:radial-gradient(rgba(255,255,255,.06) 1px,transparent 1px);background-size:6px 6px}
.stage .wrap{display:grid;grid-template-columns:1.05fr 1fr;gap:26px;align-items:center}
.stage .kick{color:#cfe3d3;font-size:14px;letter-spacing:.08em}
.stage h1{color:#fff;font-size:clamp(34px,7vw,58px);margin:.05em 0 .15em}
.stage h1 em{color:#ffd45e}
.stage p{max-width:30em;color:#e7efe5}
.stage .stats{color:#cfe3d3}.stage .stats b{color:#ffd45e}
.stage .chalk{display:flex;flex-wrap:wrap;gap:10px;margin-top:14px;font-size:15px;color:#e7efe5}
.stage .chalk span{border:2px dashed rgba(255,255,255,.45);border-radius:8px;padding:2px 10px}
.board{background:rgba(0,0,0,.18);border:3px solid rgba(255,255,255,.35);border-radius:14px;padding:10px 12px 12px}
.fib{width:100%;aspect-ratio:1/1;max-height:420px;display:block}
.fib .sqr{fill:rgba(255,255,255,.05);stroke:rgba(255,255,255,.7);stroke-width:.5}.fib .sqr.a{fill:rgba(255,212,94,.08)}
.fib .sqt{fill:rgba(255,255,255,.75);text-anchor:middle;dominant-baseline:central;font-family:"Zen Maru Gothic",sans-serif}
.fib .spiral{fill:none;stroke:#ffd45e;stroke-width:1.1;stroke-linecap:round}
.bcap{display:flex;justify-content:space-between;flex-wrap:wrap;gap:4px 14px;font-size:15px}.bcap b{color:#ffd45e;font-size:19px}.bl{color:#cfe3d3;font-size:13px}
.bsl{display:block;font-size:13px;color:#cfe3d3;margin-top:4px}.bsl input{width:100%;accent-color:#ffd45e}
.bnote{font-size:12.5px;color:#cfe3d3;line-height:1.6;margin-top:4px}
.stage+.wrap .nav{margin-top:18px}
@media(max-width:700px){.stage .wrap{grid-template-columns:1fr}.stage{padding:24px 0}}
@media(prefers-reduced-motion:no-preference){.fib .spiral{stroke-dasharray:600;stroke-dashoffset:0;animation:chalk 1.6s ease-out}@keyframes chalk{from{stroke-dashoffset:600}to{stroke-dashoffset:0}}}
.tree{min-width:0!important}
.toback{display:inline-block;color:#cfe3d3;font-size:14px;margin-bottom:10px}.toback:hover{color:#ffd45e}
.thumb .th-img{width:100%;height:100%;object-fit:cover;display:block}
.thumb:has(.th-img){background:none;height:auto;aspect-ratio:16/9;border-bottom:2px solid var(--ink)}
.cfig{margin:14px 0 0}.cfig img{width:100%;height:auto;display:block;border-radius:14px;border:2px solid var(--ink);box-shadow:3px 4px 0 var(--ink)}
.cfig figcaption{font-size:12px;color:var(--mute);text-align:right;margin-top:6px}
/* ===== 読み物（コラム）レイアウト ===== */
.article{max-width:40em;margin:22px auto 0}
.article .lead{font-family:"Shippori Mincho",serif;font-size:clamp(18px,3.4vw,21px);line-height:2;font-weight:600;border-left:6px solid var(--accent);padding:2px 0 2px 16px;margin:6px 0 26px}
.article .asec{margin:34px 0}
.article .asec h2{font-size:clamp(22px,4vw,27px);margin:0 0 12px;padding:0;border:0;line-height:1.5}
.article .asec h2::before{content:"";display:block;width:44px;height:5px;background:var(--accent);border-radius:3px;margin-bottom:10px}
.article .asec p{font-size:17px;line-height:2.05;margin:0 0 1.05em;letter-spacing:.02em}
.abox{background:#fff8dc;border:2px solid #ead9a0;border-radius:14px;padding:12px 16px;margin:14px 0;font-size:15.5px}
.abox b{display:block;margin-bottom:4px}.abox p{font-size:15.5px!important;margin:0 0 .6em!important}
.gbox{margin:26px 0}.gbox h2{font-size:22px;margin:0 0 8px}
.wgbox{margin:30px -6px;padding:14px 14px 12px;background:#fff;border:2px solid var(--ink);border-radius:16px;box-shadow:3px 4px 0 var(--ink)}
.wgcap{display:inline-block;background:var(--accent);color:#fff;font-weight:700;font-size:13px;border-radius:999px;padding:1px 12px;margin-bottom:6px}
.wgintro{margin:4px 0 8px;font-size:15px}
.wgbox .wg{border:0;padding:0;margin:0}
.article .math{white-space:pre-wrap;overflow-wrap:anywhere}

.psec{margin:0 0 34px}
.phead{display:flex;align-items:center;gap:8px;font-size:1.35rem;margin:0 0 4px;padding-bottom:6px;border-bottom:3px solid var(--accent);color:var(--accent)}
.phead small{margin-left:auto;font-size:.8rem;color:#777;font-weight:400}
.pdesc{margin:0 0 12px;color:#555;font-size:.92rem}

.repnote{margin:26px 0 0;font-size:.88rem;color:#666;text-align:center}
.repnote a{color:inherit;text-decoration:underline}