:root{--bg:#f7f6f2;--card:#fff;--ink:#1d2430;--sub:#5b6574;--line:#d9d6cc;--acc:#0f5c73;--acc2:#b4472c;--soft:#e8f0f2;--ok:#2d7a4f;--ng:#b4472c}
@media(prefers-color-scheme:dark){:root{--bg:#14181f;--card:#1c222c;--ink:#e6e9ee;--sub:#9aa5b5;--line:#313a48;--acc:#6cc0d8;--acc2:#f08a6c;--soft:#1f2c34;--ok:#6ccf99;--ng:#f08a6c}}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--bg);color:var(--ink);font-family:"Noto Sans JP","Hiragino Sans","Yu Gothic",sans-serif;line-height:1.85;font-size:16px}
a{color:var(--acc)}
header.top{border-bottom:1px solid var(--line);background:var(--card)}
header.top div{max-width:760px;margin:0 auto;padding:12px 16px;display:flex;justify-content:space-between;align-items:baseline;gap:12px;flex-wrap:wrap;font-size:14px}
header.top .brand{font-family:"Shippori Mincho",serif;font-weight:800;font-size:18px;color:var(--ink);text-decoration:none}
main{max-width:760px;margin:0 auto;padding:24px 16px 48px}
h1{font-family:"Shippori Mincho",serif;font-size:28px;line-height:1.4;margin:.2em 0 .4em}
h2{font-family:"Shippori Mincho",serif;font-size:20px;margin:2em 0 .5em;padding-bottom:.25em;border-bottom:2px solid var(--acc)}
.pill{display:inline-block;font-size:12px;color:var(--acc);border:1px solid var(--acc);border-radius:3px;padding:0 8px;margin-right:6px;letter-spacing:.05em}
.question{font-family:"Shippori Mincho",serif;font-size:20px;line-height:1.7;background:var(--soft);border-left:4px solid var(--acc);padding:14px 16px;margin:16px 0}
.lead{color:var(--sub);margin:.2em 0 1em}
.step{margin:1em 0}.step b.h{display:block;color:var(--acc);font-size:15px}
.math{font-family:"Noto Sans JP",monospace;background:var(--soft);padding:6px 10px;border-radius:4px;display:inline-block;margin:4px 0}
.one{font-family:"Shippori Mincho",serif;font-size:19px;font-weight:700;text-align:center;border-top:1px solid var(--line);border-bottom:1px solid var(--line);padding:14px 8px;margin:24px 0}
.card{background:var(--card);border:1px solid var(--line);border-radius:6px;padding:14px 16px;margin:16px 0}
.card h3{margin:0 0 6px;font-size:15px;color:var(--sub);font-weight:700}
.note{font-size:13px;color:var(--sub);line-height:1.7}
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(230px,1fr));gap:12px}
.item{display:block;background:var(--card);border:1px solid var(--line);border-radius:6px;padding:12px 14px;text-decoration:none;color:var(--ink)}
.item:hover{border-color:var(--acc)}
.item .t{font-weight:700}.item .q{font-size:13px;color:var(--sub);margin-top:2px;line-height:1.6}
.item.stub{opacity:.55}
.pillar{margin:28px 0 8px;font-family:"Shippori Mincho",serif;font-size:18px}
.pillar small{color:var(--sub);font-family:inherit;font-size:13px;margin-left:8px}
svg.ch{width:100%;height:auto;display:block}
svg.ch text{fill:var(--sub);font-size:11px;font-family:inherit}
.ctrl{display:flex;flex-wrap:wrap;gap:14px;align-items:center;margin:8px 0;font-size:14px}
.ctrl label{display:flex;gap:6px;align-items:center}
.ctrl input[type=range]{width:160px}
button,.btn{font:inherit;font-size:14px;background:var(--card);color:var(--ink);border:1px solid var(--acc);border-radius:4px;padding:3px 12px;cursor:pointer}
button.on{background:var(--acc);color:var(--card)}
.read{font-size:14px;background:var(--soft);padding:8px 12px;border-radius:4px;margin:8px 0;min-height:2.4em}
.q2{margin:12px 0}.q2 .opts{display:flex;flex-direction:column;gap:6px;margin-top:6px}
.q2 button{text-align:left}.q2 .res{font-size:14px;margin-top:6px}
.ok{color:var(--ok)}.ng{color:var(--ng)}
table.num{border-collapse:collapse;width:100%;font-size:13px}table.num td,table.num th{border-bottom:1px solid var(--line);padding:4px 6px;text-align:left;vertical-align:top}
ul.src{font-size:13px;padding-left:1.2em}
.badge{font-size:12px;border:1px solid var(--line);border-radius:3px;padding:0 6px;color:var(--sub)}
.warn{border:1px solid var(--acc2);border-left-width:4px;padding:8px 12px;font-size:14px;margin:16px 0;background:var(--card)}
footer{max-width:760px;margin:0 auto;padding:16px;border-top:1px solid var(--line);font-size:13px;color:var(--sub)}
.nav2{display:flex;justify-content:space-between;gap:8px;margin-top:24px;font-size:14px}
/* ---- v2: ノート・方眼の世界観 ---- */
:root{--peg:#9aa3ad;--grid:rgba(15,92,115,.07)}
@media(prefers-color-scheme:dark){:root{--peg:#5b6574;--grid:rgba(108,192,216,.07)}}
body{background-color:var(--bg);background-image:linear-gradient(var(--grid) 1px,transparent 1px),linear-gradient(90deg,var(--grid) 1px,transparent 1px);background-size:24px 24px}
header.top{background:color-mix(in srgb,var(--card) 88%,transparent);backdrop-filter:blur(4px)}
.hero{display:grid;grid-template-columns:1fr 1.35fr;gap:24px;align-items:center;margin:8px 0 12px}
.kicker{font-size:12px;letter-spacing:.2em;color:var(--acc);margin:0;font-weight:700}
.hero h1{font-size:40px;margin:.1em 0 .2em;line-height:1.25}
.hero h1 span{display:block;font-size:20px;color:var(--acc);margin-top:.2em;font-weight:600}
.hint{font-size:13px;color:var(--sub);border-left:3px solid var(--acc2);padding-left:10px}
.hero-v{background:var(--card);border:1px solid var(--line);border-radius:8px;padding:8px;box-shadow:0 2px 0 var(--line),0 10px 24px -12px rgba(0,0,0,.25);position:relative}
canvas.galton{width:100%;height:auto;display:block;cursor:pointer}
.note.wide{margin:8px 0 4px}
.pillar{display:flex;align-items:center;gap:10px;margin:34px 0 10px;font-size:19px}
.pillar .pk{display:inline-flex;width:30px;height:30px;border-radius:50%;background:var(--pc);color:#fff;font-family:inherit;font-weight:700;font-size:15px;align-items:center;justify-content:center}
.item{padding:0;overflow:hidden;position:relative;box-shadow:0 2px 0 var(--line);transition:transform .15s,box-shadow .15s}
a.item:hover{transform:translateY(-3px);box-shadow:0 8px 16px -8px rgba(0,0,0,.3)}
.item .tp{background:color-mix(in srgb,var(--pc) 9%,var(--card));border-bottom:1px dashed var(--line);padding:6px 10px 2px}
.item .tp svg{width:100%;height:auto;display:block;max-height:92px}
.item .bd{padding:10px 14px 12px}
.item::before{content:"";position:absolute;top:-6px;left:50%;width:52px;height:16px;margin-left:-26px;background:color-mix(in srgb,var(--pc) 22%,transparent);transform:rotate(-2deg);z-index:1}
.item.stub{opacity:.7}.item.stub .tp{filter:grayscale(1);opacity:.6}
.grid{grid-template-columns:repeat(auto-fill,minmax(250px,1fr));gap:18px 14px}
@media(max-width:700px){.hero{grid-template-columns:1fr}.hero h1{font-size:32px}}
main.home{padding-top:0}main.home .hero{margin-top:0;min-height:430px;padding-top:28px}@media(max-width:700px){main.home .hero{min-height:0;padding-top:20px}}
main.home .hero{width:min(1120px,100vw);margin-left:calc(50% - min(560px,50vw));padding:36px 20px 20px;grid-template-columns:1fr 1.5fr;min-height:480px;box-sizing:border-box}
main.home .hero h1{font-size:46px}
@media(max-width:1130px){main.home .hero{width:auto;margin-left:0;padding:28px 0 12px}}
@media(max-width:900px){main.home .hero{grid-template-columns:1fr;min-height:0}main.home .hero h1{font-size:34px}}
.tools{display:flex;flex-wrap:wrap;gap:10px;margin:6px 0 10px}
.tools a{background:var(--card);border:1px solid var(--line);border-bottom-width:3px;border-radius:6px;padding:8px 14px;text-decoration:none;color:var(--ink);font-size:14px;font-weight:700}
.tools a:hover{border-color:var(--acc)}
/* thumb v2 */
svg.thumb{max-height:128px}
.thumb .pf{fill:var(--pc)}.thumb .pa{fill:var(--pc);opacity:.14}.thumb .pa2{fill:var(--pc);opacity:.38}
.thumb .of{fill:var(--acc2)}.thumb .tr{fill:var(--line)}.thumb .op{fill:none;stroke:var(--sub);stroke-width:1.2;stroke-dasharray:3 3}
.thumb .ps2{fill:none;stroke:var(--pc);stroke-width:2.4;stroke-linecap:round;stroke-linejoin:round}
.thumb .ps2d{stroke:var(--pc);stroke-width:1.6;stroke-dasharray:3 3}
.thumb .os2{fill:none;stroke:var(--acc2);stroke-width:2.2;stroke-linecap:round;stroke-linejoin:round}
.thumb .os2d{fill:none;stroke:var(--acc2);stroke-width:1.8;stroke-dasharray:5 4;stroke-linecap:round}
.thumb .os{stroke:var(--acc2);stroke-width:1.8;fill:none;stroke-linecap:round}
.thumb .ax{stroke:var(--sub);stroke-width:1.4}.thumb .gl{stroke:var(--line);stroke-width:1}
.thumb .tt{fill:var(--sub);font-size:10px;font-family:"Noto Sans JP",sans-serif;font-weight:500}
.thumb .tw{fill:#fff;font-size:10px;font-family:"Noto Sans JP",sans-serif;font-weight:700}
.thumb .big{fill:var(--pc);font-size:30px;font-weight:800;font-family:"Shippori Mincho",serif}
.item .tp{padding:8px 10px 4px}
.item .tp svg,svg.thumb{max-height:none}
/* chapter header & chart polish */
.chead{display:grid;grid-template-columns:1fr 230px;gap:20px;align-items:center;margin-bottom:8px}
.chead h1{margin:.3em 0 .1em}
.cthumb{background:color-mix(in srgb,var(--pc) 10%,var(--card));border:1px solid var(--line);border-radius:8px;padding:6px 8px;box-shadow:0 2px 0 var(--line);position:relative}
.cthumb::before{content:"";position:absolute;top:-7px;left:50%;width:48px;height:14px;margin-left:-24px;background:color-mix(in srgb,var(--pc) 24%,transparent);transform:rotate(-2deg)}
.cthumb svg{width:100%;height:auto;display:block}
@media(max-width:700px){.chead{grid-template-columns:1fr}.cthumb{max-width:300px}}
svg.ch text{font-size:13px;fill:var(--sub);font-weight:500}
svg.ch rect{rx:2px}
svg.ch line{shape-rendering:crispEdges}
svg.ch circle{filter:none}
#widget.card{padding:16px 18px;background:linear-gradient(var(--card),var(--card));box-shadow:0 2px 0 var(--line)}
/* top page: wider, 3-4 column card grid */
main.home{max-width:1120px;padding-left:20px;padding-right:20px}
main.home .hero{width:auto;margin-left:0}
main.home .grid{grid-template-columns:repeat(auto-fill,minmax(250px,1fr))}
@media(max-width:700px){main.home{padding-left:16px;padding-right:16px}}