:root{--bg:#f7f7f4;--fg:#1b1b1b;--accent:#1d5fd1;--accent-soft:#e3ecfb;--dim:#666b73;--border:#d7d9dc;--card:#fff;--code:#f1f2f3;--ok:#18794e;--r:8px;--hdr:56px;--shadow:0 6px 24px rgba(0,0,0,.12)}
@media (prefers-color-scheme:dark){:root{--bg:#111214;--fg:#e6e6e8;--accent:#7aa7f5;--accent-soft:#1b2537;--dim:#9aa0a8;--border:#33363b;--card:#1a1b1e;--code:#1f2124;--ok:#4fc38a;--shadow:0 6px 24px rgba(0,0,0,.5)}}
*,*::before,*::after{box-sizing:border-box;margin:0}
html{scroll-padding-top:calc(var(--hdr) + 12px);-webkit-text-size-adjust:100%}
@media (prefers-reduced-motion:no-preference){html{scroll-behavior:smooth}}
body{font-family:'Noto Sans JP',system-ui,sans-serif;background:var(--bg);color:var(--fg);line-height:1.8}
body.nav-open{overflow:hidden}
a{color:var(--accent);text-decoration:none}a:hover{text-decoration:underline}
:focus-visible{outline:2px solid var(--accent);outline-offset:2px;border-radius:4px}
.skip{position:absolute;left:-999px;top:0;background:var(--accent);color:#fff;padding:.5rem 1rem;z-index:100}.skip:focus{left:8px;top:8px}
.wrap{max-width:780px;margin:0 auto;padding:0 16px}

/* ヘッダー */
header.site{position:sticky;top:0;z-index:30;height:var(--hdr);background:color-mix(in srgb,var(--bg) 88%,transparent);backdrop-filter:blur(10px);-webkit-backdrop-filter:blur(10px);border-bottom:1px solid var(--border)}
header.site .wrap{height:100%;display:flex;align-items:center;justify-content:space-between;gap:.5rem}
.logo{display:flex;align-items:center;gap:.5rem;font-weight:700;color:var(--fg);font-size:1.02rem}
.logo:hover{text-decoration:none}
.logo .mark{display:grid;place-items:center;width:32px;height:32px;border-radius:8px;background:var(--accent);color:#fff;font-size:1rem;font-weight:700;flex:none}
.logo .lt{display:flex;flex-direction:column;line-height:1.15}
.logo .ln{font-size:1.08rem;font-weight:700;letter-spacing:.04em}
.logo .ls{font-size:.68rem;font-weight:400;color:var(--dim)}
.hdr-nav{display:flex;align-items:center;gap:.15rem}
.hdr-nav .txt{color:var(--dim);font-size:.88rem;padding:.4rem .6rem;border-radius:6px}
.hdr-nav .txt:hover{color:var(--fg);background:var(--code);text-decoration:none}
.icon-btn{display:grid;place-items:center;width:42px;height:42px;border:0;border-radius:8px;background:transparent;color:var(--fg);cursor:pointer}
.icon-btn:hover{background:var(--code)}
.icon-btn svg{width:22px;height:22px}
@media (max-width:560px){.hdr-nav .txt{display:none}}

/* ハンバーガーメニュー（右から出る引き出し） */
.overlay{position:fixed;inset:0;z-index:40;background:rgba(0,0,0,.4);opacity:0;visibility:hidden;transition:opacity .2s,visibility .2s}
.drawer{position:fixed;top:0;right:0;bottom:0;z-index:50;width:min(380px,88vw);background:var(--bg);box-shadow:var(--shadow);display:flex;flex-direction:column;transform:translateX(100%);visibility:hidden;transition:transform .25s ease,visibility .25s}
body.nav-open .overlay{opacity:1;visibility:visible}
body.nav-open .drawer{transform:none;visibility:visible}
.drawer-head{display:flex;align-items:center;justify-content:space-between;padding:0 8px 0 18px;height:var(--hdr);border-bottom:1px solid var(--border);font-weight:700}
.drawer-body{overflow-y:auto;padding:14px 18px 32px;flex:1}
.search{position:relative;margin-bottom:.5rem}
.search svg{position:absolute;left:12px;top:50%;transform:translateY(-50%);width:18px;height:18px;color:var(--dim)}
.search input{width:100%;font:inherit;font-size:16px;padding:.65rem .8rem .65rem 2.4rem;border:1px solid var(--border);border-radius:10px;background:var(--card);color:var(--fg)}
.search input:focus{outline:none;border-color:var(--accent);box-shadow:0 0 0 3px var(--accent-soft)}
.search-hint{font-size:.78rem;color:var(--dim);margin-bottom:1rem}
.results{list-style:none;margin:0 0 1rem;padding:0}
.results li{margin:0}
.results a{display:block;padding:.55rem .7rem;border-radius:8px;color:var(--fg)}
.results a:hover,.results a.sel{background:var(--accent-soft);text-decoration:none}
.results .k{display:inline-block;font-size:.68rem;font-weight:700;color:var(--accent);border:1px solid var(--accent);border-radius:3px;padding:0 .3rem;margin-right:.4rem;vertical-align:1px}
.results .s{display:block;font-family:'IBM Plex Mono',monospace;font-size:.82rem;color:var(--dim)}
.results .none{color:var(--dim);font-size:.9rem;padding:.5rem .2rem}
.nav-sec{margin-top:1.1rem}
.nav-sec h4{font-size:.75rem;color:var(--dim);letter-spacing:.06em;margin-bottom:.35rem}
.nav-sec ul{list-style:none;margin:0;padding:0}
.nav-sec li{margin:0}
.nav-sec a{display:flex;justify-content:space-between;align-items:center;padding:.5rem .6rem;border-radius:8px;color:var(--fg)}
.nav-sec a:hover{background:var(--code);text-decoration:none}
.nav-sec a[aria-current]{background:var(--accent-soft);color:var(--accent);font-weight:700}
.nav-sec .n{font-size:.75rem;color:var(--dim)}
.chips{display:flex;flex-wrap:wrap;gap:.4rem}
.chips a{display:inline-block;padding:.25rem .65rem;border:1px solid var(--border);border-radius:999px;font-size:.85rem;color:var(--fg)}
.chips a:hover{border-color:var(--accent);color:var(--accent);text-decoration:none}

/* 本文 */
main{padding:1.2rem 0 3rem}
nav.bc{font-size:.8rem;color:var(--dim);margin-bottom:.75rem;overflow-x:auto;white-space:nowrap}nav.bc a{color:var(--dim)}
h1{font-size:1.5rem;line-height:1.4;margin-bottom:.6rem}
h2{font-size:1.12rem;margin:2.2rem 0 .8rem;padding-bottom:.3rem;border-bottom:2px solid var(--accent)}
h3{font-size:1rem;margin:1.4rem 0 .5rem}
p{margin-bottom:1rem}ul,ol{margin:0 0 1rem 1.3rem}li{margin-bottom:.35rem}
.lead{color:var(--dim)}
.mono,code{font-family:'IBM Plex Mono',ui-monospace,monospace}
.toc{margin:1rem 0 .5rem;padding:.7rem .8rem;background:var(--card);border:1px solid var(--border);border-radius:var(--r)}
.toc b{display:block;font-size:.75rem;color:var(--dim);margin-bottom:.4rem}
.hero{background:var(--accent-soft);border:2px solid var(--accent);border-radius:var(--r);padding:1.2rem 1.25rem;margin:1.2rem 0;text-align:center}
.hero .big{font-family:'IBM Plex Mono',ui-monospace,monospace;font-size:1.45rem;font-weight:600;overflow-wrap:anywhere}
.hero .sub{color:var(--dim);font-size:.85rem;margin-top:.3rem}
.step{background:var(--card);border:1px solid var(--border);border-radius:var(--r);padding:.9rem 1rem;margin-bottom:.8rem}
.step .st{margin-bottom:.35rem;font-size:.95rem}.step p{margin:.2rem 0 .3rem}.step .lead{font-size:.85rem}
details.pre{margin-bottom:.9rem}details.pre summary{cursor:pointer;color:var(--dim);font-size:.9rem;margin-bottom:.6rem}
.calc{font-family:'IBM Plex Mono',ui-monospace,monospace;background:var(--code);border-left:3px solid var(--accent);padding:.6rem .9rem;margin:.5rem 0 .2rem;border-radius:0 var(--r) var(--r) 0;overflow-x:auto;white-space:nowrap;font-size:.92rem;line-height:2}
.ok{color:var(--ok);font-weight:700}
table{width:100%;border-collapse:collapse;margin-bottom:1rem;font-size:.92rem}
th,td{text-align:left;padding:.45rem .5rem;border-bottom:1px solid var(--border);vertical-align:top}
th{font-size:.8rem;color:var(--dim);font-weight:700}
td.mono{white-space:nowrap}
.tbl{overflow-x:auto}
.note{background:var(--card);border:1px dashed var(--border);border-radius:var(--r);padding:.8rem 1rem;margin:1rem 0;font-size:.92rem}
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(200px,1fr));gap:.6rem;margin-bottom:1rem}
.grid a{display:block;background:var(--card);border:1px solid var(--border);border-radius:var(--r);padding:.6rem .8rem;color:var(--fg);transition:border-color .15s,transform .15s}
.grid a:hover{border-color:var(--accent);text-decoration:none;transform:translateY(-1px)}
.grid .u{font-family:'IBM Plex Mono',ui-monospace,monospace;color:var(--accent);font-size:.9rem}
.cat-cards a{padding:.85rem 1rem}
.cat-cards .t{font-weight:700}
.cat-cards .d{font-size:.82rem;color:var(--dim);line-height:1.6;margin-top:.2rem}
.cat-cards .n{font-size:.75rem;color:var(--accent);margin-top:.35rem}
.tag{display:inline-block;font-size:.72rem;font-weight:700;color:var(--accent);background:var(--accent-soft);border-radius:3px;padding:.05rem .45rem;margin-right:.3rem}
.home-search{display:flex;align-items:center;gap:.6rem;width:100%;margin:1rem 0 .5rem;padding:.8rem 1rem;border:1px solid var(--border);border-radius:12px;background:var(--card);color:var(--dim);font:inherit;font-size:.95rem;cursor:pointer;text-align:left}
.home-search:hover{border-color:var(--accent)}
.home-search svg{width:18px;height:18px;flex:none}

/* フッター・トップへ戻る */
footer.site{border-top:1px solid var(--border);padding:1.6rem 0 2.5rem;font-size:.82rem;color:var(--dim)}
footer.site .links{display:flex;flex-wrap:wrap;gap:.4rem 1rem;margin-bottom:.8rem}
footer.site a{color:var(--dim)}
.to-top{position:fixed;right:16px;bottom:16px;z-index:20;width:44px;height:44px;border-radius:50%;border:1px solid var(--border);background:var(--card);color:var(--fg);box-shadow:var(--shadow);cursor:pointer;display:grid;place-items:center;opacity:0;visibility:hidden;transition:opacity .2s,visibility .2s}
.to-top.show{opacity:1;visibility:visible}
.to-top svg{width:20px;height:20px}
.tag.lv{color:var(--dim);background:var(--code)}
.goals{margin:1rem 0;padding:.8rem 1rem;border-left:4px solid var(--ok);background:var(--card);border-radius:0 var(--r) var(--r) 0}
.goals b{font-size:.85rem}.goals ul{margin:.3rem 0 0 1.2rem}.goals li{margin:.15rem 0;font-size:.92rem}
.meaning{font-size:1.05rem;padding:.2rem 0}
.wordeq{margin:1rem 0;padding:.9rem 1rem;border:2px dashed var(--accent);border-radius:var(--r);background:var(--card)}
.wordeq .lbl{font-size:.75rem;font-weight:700;color:var(--accent);margin-bottom:.2rem}
.wordeq .eq{font-size:1.08rem;font-weight:700;line-height:1.7}
table.swap td:first-child{font-weight:700}
table.swap th:last-child,table.swap td:last-child{white-space:nowrap}
.unitname{border-style:solid;border-color:var(--accent);background:var(--accent-soft)}
.summary{margin:2rem 0 1rem;padding:.9rem 1.1rem;background:var(--accent-soft);border-radius:var(--r)}
.summary ul{margin:.3rem 0 0 1.2rem}.summary li{margin:.2rem 0}
.quiz{background:var(--card);border:1px solid var(--border);border-radius:var(--r);padding:1rem}
.quiz .opts{list-style:none;margin:.4rem 0 .8rem;padding:0;display:grid;gap:.4rem}
.quiz .opts li{display:flex;align-items:center;gap:.6rem;padding:.45rem .7rem;border:1px solid var(--border);border-radius:8px;margin:0}
.quiz .opt{display:grid;place-items:center;width:24px;height:24px;border-radius:50%;background:var(--code);font-size:.78rem;font-weight:700;flex:none}
.quiz details summary{cursor:pointer;color:var(--accent);font-weight:700}
.quiz details p{margin:.5rem 0 0}
footer.site .src{font-size:.78rem;margin:0 0 .5rem}
.practice{display:grid;gap:1rem}
.pq{background:var(--card);border:1px solid var(--border);border-radius:var(--r);padding:1rem}
.pq .qt{margin-bottom:.6rem}
.pq .qn{display:inline-block;background:var(--accent);color:#fff;font-size:.75rem;font-weight:700;border-radius:4px;padding:.05rem .45rem;margin-right:.45rem}
.pq .u{color:var(--accent);font-size:.9em;white-space:nowrap}
.pq .opts{list-style:none;margin:0 0 .7rem;padding:0;display:grid;gap:.45rem}
.pq .opts li{margin:0}
.ch{display:flex;align-items:center;gap:.6rem;width:100%;text-align:left;font:inherit;color:var(--fg);background:var(--bg);border:1px solid var(--border);border-radius:8px;padding:.55rem .7rem;cursor:pointer;transition:border-color .15s,background .15s}
.ch:hover:not(:disabled){border-color:var(--accent)}
.ch:disabled{cursor:default}
.ch .opt{display:grid;place-items:center;width:24px;height:24px;border-radius:50%;background:var(--code);font-size:.78rem;font-weight:700;flex:none}
.ch.right{border-color:var(--ok);background:color-mix(in srgb,var(--ok) 12%,var(--bg))}
.ch.right .opt{background:var(--ok);color:#fff}
.ch.wrong{border-color:#c2410c;background:color-mix(in srgb,#c2410c 10%,var(--bg))}
.ch.wrong .opt{background:#c2410c;color:#fff}
.pq .res{font-weight:700;margin:.2rem 0 .4rem}.pq .res.ng{color:#c2410c}
.pq .exp summary{cursor:pointer;color:var(--accent);font-weight:700;font-size:.92rem}
.pq .exp p{margin:.5rem 0 0;font-size:.95rem}
.mission{margin:.6rem 0 1.4rem;padding:1.2rem 1.25rem;border-radius:var(--r);background:var(--card);border:1px solid var(--border)}
.mission .quote{font-size:1.15rem;font-weight:700;line-height:1.6;margin:0}
.mission .quote-src{color:var(--dim);font-size:.85rem;margin:.3rem 0 0}
.steps3{margin:0 0 1rem 1.4rem}.steps3 li{margin:.6rem 0}
.problem{background:var(--card);border:1px solid var(--border);border-radius:var(--r);padding:.8rem 1rem;margin:1rem 0}
.problem b{font-size:.8rem;color:var(--dim)}.problem p{margin:.2rem 0 0}
.answer{display:flex;align-items:center;gap:.8rem;flex-wrap:wrap;padding:.7rem 1rem;border-radius:var(--r);margin:.8rem 0;font-size:1.1rem}
.answer .lbl{font-size:.75rem;font-weight:700;border-radius:4px;padding:.1rem .5rem;color:#fff}
.wrong-ans{background:color-mix(in srgb,#c2410c 8%,var(--card));border:1px solid #c2410c}.wrong-ans .lbl{background:#c2410c}
.right-ans{background:color-mix(in srgb,var(--ok) 10%,var(--card));border:1px solid var(--ok)}.right-ans .lbl{background:var(--ok)}
.ng{color:#c2410c;font-weight:700}
.verdict{padding:.6rem .8rem;border-radius:8px;margin:.4rem 0 0}
.verdict.ng{background:color-mix(in srgb,#c2410c 8%,var(--card));font-weight:400}
.verdict.warn{background:color-mix(in srgb,#b45309 10%,var(--card))}
.tag.warn{color:#b45309;background:color-mix(in srgb,#b45309 12%,var(--bg))}
.given{list-style:none;margin:.3rem 0 .2rem;padding:0;display:flex;flex-wrap:wrap;gap:.3rem 1rem;font-size:.92rem}
.given li{margin:0}
.mcards .u{font-size:.82rem}
.feat .d,.mcards .d{font-size:.85rem;color:var(--dim);line-height:1.6;margin-top:.2rem}
.feat .t{font-weight:700}
.checkbox{margin:1rem 0;padding:.8rem 1rem;border-radius:var(--r);border:2px solid var(--ok);background:color-mix(in srgb,var(--ok) 6%,var(--card))}
.checkbox b{font-size:.85rem;color:var(--ok)}
.pitfall{border:2px solid #c2410c;border-style:solid;background:color-mix(in srgb,#c2410c 6%,var(--card))}.pitfall b{color:#c2410c}.checkbox p{margin:.3rem 0 0}
.tipbox{margin:1rem 0;padding:.9rem 1.1rem;border-radius:var(--r);border-left:5px solid var(--accent);background:var(--accent-soft)}
.tipbox b{color:var(--accent);font-size:1.02rem}.tipbox p{margin:.35rem 0 0}
.themes a .t{font-weight:700}.themes a .d{font-size:.8rem;color:var(--dim)}
.lead.tiny{font-size:.88rem}
.mk-line{display:flex;align-items:center;flex-wrap:wrap;gap:.35rem .5rem;margin-top:.35rem}
.mk{display:inline-grid;place-items:center;width:1.4rem;height:1.4rem;border-radius:4px;font-size:.72rem;font-weight:700;color:#fff;flex:none}
.mk.bad{background:#c2410c}.mk.good{background:var(--ok);margin-left:.4rem}
.mk-line .u{color:var(--fg);font-size:.95rem}
.tag.adv{color:#7c3aed;background:color-mix(in srgb,#7c3aed 12%,var(--bg))}
.tnav{margin:.5rem 0 1.2rem}.tnav a[aria-current]{background:var(--accent);color:#fff;border-color:var(--accent)}
.pq .qt .given{margin-top:.5rem}
/* 数式（ノート風の表記） */
math{font-family:"Cambria Math","STIX Two Math","Latin Modern Math","Noto Sans Math",math;font-size:1.12em}
.calc{line-height:2.6;white-space:nowrap}
.calc math{font-size:1.18em}
.hero .big math{font-size:1.2em}
.pq .ch math{font-size:1.15em}
.u math,.grid .u math{font-size:1em}
.results .s math{font-size:1em}
td math{font-size:1.05em}

/* 重要な部分を目立たせる */
.ok{color:var(--ok);font-weight:700;font-size:1.08em}
.ng{color:#c2410c;font-weight:700;font-size:1.08em}
.key{color:#c2410c;font-weight:700;font-size:1.08em}
.steps3 b{color:var(--accent);font-size:1.08em}
.meaning b{color:var(--accent);font-size:1.1em}
.wordeq .eq{font-size:1.18rem}
.answer .mono{font-size:1.3rem;font-weight:700}
.verdict{font-size:1.05rem}.verdict.ng b{color:#c2410c;font-size:1.1em}.verdict.warn b{color:#b45309}
.checkbox .ok{font-size:1.2em}
.summary li{font-size:1.02rem}
main .lead b{color:var(--accent)}
h1{color:var(--fg)}
.mission .quote{color:var(--accent);font-size:1.25rem}