:root{--navy:#0b1f3a;--blue:#1d4ed8;--blue-d:#1e3a8a;--muted:#475569;--line:#d9e2f1;--soft:#f3f7ff;--bg:#fff;--ok:#146c2e;--err:#b42318}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;background:var(--bg);color:var(--navy);font:1rem/1.65 system-ui,-apple-system,"Segoe UI",Roboto,Helvetica,Arial,sans-serif}
[hidden]{display:none!important}
a{color:var(--blue);text-underline-offset:2px}
a:hover{color:var(--blue-d)}
:focus-visible{outline:3px solid var(--blue);outline-offset:2px;border-radius:3px}
h1,h2,h3{line-height:1.25;margin:1.6em 0 .5em;color:var(--navy)}
h1{font-size:clamp(1.8rem,4.5vw,2.6rem);margin-top:.6em}
h2{font-size:1.5rem}
h3{font-size:1.15rem;margin:.4em 0}
p{margin:.7em 0}
.wrap{max-width:1100px;margin:0 auto;padding:0 1.25rem}
.narrow{max-width:780px}
.small{font-size:.9rem;color:var(--muted)}
.lead{font-size:1.15rem;color:var(--muted);max-width:46rem}
.skip{position:absolute;left:-999px;top:0;background:var(--navy);color:#fff;padding:.6rem 1rem;z-index:100}
.skip:focus{left:0}
.site-header{border-bottom:1px solid var(--line);background:#fff;position:sticky;top:0;z-index:50}
.bar{display:flex;align-items:center;justify-content:space-between;gap:1rem;min-height:64px}
.brand{display:flex;align-items:center;gap:.55rem;font-weight:800;font-size:1.2rem;color:var(--navy);text-decoration:none}
.bar nav ul,.foot ul{list-style:none;margin:0;padding:0;display:flex;flex-wrap:wrap;gap:.25rem 1.1rem}
.bar nav a{display:block;padding:.5rem .15rem;color:var(--navy);text-decoration:none;font-weight:600;border-bottom:2px solid transparent}
.bar nav a:hover,.bar nav a[aria-current="page"]{border-bottom-color:var(--blue);color:var(--blue)}
.menu-btn{display:none;background:#fff;border:1px solid var(--line);border-radius:8px;padding:.5rem .9rem;font:inherit;font-weight:600;color:var(--navy);cursor:pointer}
@media (max-width:760px){
 .js .menu-btn{display:block}
 .bar{flex-wrap:wrap;padding-top:.4rem;padding-bottom:.4rem}
 .bar nav{width:100%}
 .js .bar nav{display:none}
 .js .bar nav.open{display:block}
 .bar nav ul{flex-direction:column;gap:0}
 .bar nav a{padding:.7rem .2rem;border-bottom:1px solid var(--line)}
}
.hero{background:linear-gradient(180deg,var(--soft),#fff);padding:2.5rem 0 2rem}
.eyebrow{color:var(--blue);font-weight:700;letter-spacing:.04em;text-transform:uppercase;font-size:.85rem;margin:0}
.band{background:var(--soft);padding:1.5rem 0 2rem;margin:2rem 0}
.btns{display:flex;flex-wrap:wrap;gap:.6rem;margin:1rem 0}
.btn{display:inline-block;background:var(--blue);color:#fff;border:2px solid var(--blue);border-radius:8px;padding:.6rem 1.1rem;font:inherit;font-weight:700;cursor:pointer;text-decoration:none}
.btn:hover{background:var(--blue-d);border-color:var(--blue-d);color:#fff}
.btn.secondary{background:#fff;color:var(--blue)}
.btn.secondary:hover{background:var(--soft);color:var(--blue-d)}
.card{background:#fff;border:1px solid var(--line);border-radius:12px;padding:1.1rem 1.2rem}
.grid{list-style:none;margin:1rem 0;padding:0;display:grid;grid-template-columns:repeat(auto-fill,minmax(250px,1fr));gap:1rem}
.tool-card h3 a,.grid h3 a{color:var(--navy);text-decoration:none}
.tool-card h3 a:hover,.grid h3 a:hover{color:var(--blue);text-decoration:underline}
.tag{display:inline-block;background:var(--soft);color:var(--blue-d);border:1px solid var(--line);border-radius:999px;padding:.05rem .6rem;font-size:.8rem;font-weight:700}
.dir label,.tool label,.tool legend{display:block;font-weight:700;margin:.8rem 0 .3rem}
input[type=text],input[type=search],select,textarea{width:100%;max-width:100%;border:1px solid #94a3b8;border-radius:8px;padding:.6rem .75rem;font:inherit;color:var(--navy);background:#fff}
textarea{resize:vertical;font-family:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;font-size:.95rem}
textarea[readonly],input[readonly]{background:var(--soft)}
.chips{display:flex;flex-wrap:wrap;gap:.5rem;margin:.8rem 0}
.chip{border:1px solid var(--line);background:#fff;color:var(--navy);border-radius:999px;padding:.35rem .9rem;font:inherit;font-weight:600;cursor:pointer}
.chip[aria-pressed=true]{background:var(--blue);border-color:var(--blue);color:#fff}
.crumbs{font-size:.9rem;color:var(--muted);margin-top:1.2rem}
.tool{margin:1.2rem 0}
.stats{display:grid;grid-template-columns:repeat(auto-fit,minmax(140px,1fr));gap:.7rem;margin:1rem 0}
.stats div{background:var(--soft);border:1px solid var(--line);border-radius:10px;padding:.6rem .8rem}
.stats dt{font-size:.82rem;color:var(--muted)}
.stats dd{margin:0;font-size:1.4rem;font-weight:800}
.row{display:grid;grid-template-columns:repeat(auto-fit,minmax(200px,1fr));gap:.8rem}
fieldset{border:1px solid var(--line);border-radius:10px;margin:1rem 0;padding:.4rem 1rem .8rem}
.tool .check{display:block;font-weight:400;margin:.4rem 0}
.status,.msg{min-height:1.4em;margin:.5rem 0;font-weight:600}
.msg.ok{color:var(--ok)}
.msg.err{color:var(--err)}
.block{border-top:1px solid var(--line);padding-bottom:.6rem}
.block:first-child{border-top:0}
.result{font-size:1.2rem;font-weight:800;margin:.8rem 0}
.calc{max-width:340px;margin:0 auto}
.calc-expr{min-height:1.5em;text-align:right;color:var(--muted);padding:0 .5rem}
.calc-display{display:block;text-align:right;font-size:2rem;font-weight:800;border:1px solid var(--line);background:var(--soft);border-radius:10px;padding:.5rem .8rem;overflow-x:auto;white-space:nowrap}
.keys{display:grid;grid-template-columns:repeat(4,1fr);gap:.5rem;margin-top:.7rem}
.key{padding:.9rem 0;font:inherit;font-size:1.2rem;font-weight:700;border:1px solid var(--line);border-radius:10px;background:#fff;color:var(--navy);cursor:pointer}
.key:hover{background:var(--soft)}
.key.op,.key.fn{background:var(--soft);color:var(--blue-d)}
.key.eq{background:var(--blue);color:#fff;border-color:var(--blue)}
.key.zero{grid-column:span 2}
.links{padding-left:1.2rem}
.prose h2{margin-top:1.6em}
.prose pre{background:var(--soft);border:1px solid var(--line);border-radius:8px;padding:.8rem 1rem;overflow-x:auto}
.prose code{font-family:ui-monospace,Menlo,Consolas,monospace;font-size:.92em}
.prose li{margin:.3rem 0}
.notice{background:var(--soft);border-left:4px solid var(--blue);padding:.7rem 1rem;border-radius:4px}
.todo{background:#fff3bf;border:1px solid #d9a600;padding:.05rem .4rem;border-radius:4px;font-weight:600}
aside.card{margin:2rem 0}
.site-footer{border-top:1px solid var(--line);background:var(--soft);margin-top:3rem;padding:1.5rem 0}
.foot{display:flex;flex-wrap:wrap;gap:1.5rem;justify-content:space-between}
.foot nav a{color:var(--navy);font-weight:600}
.brand-foot{font-weight:800;margin:0}
@media (prefers-reduced-motion:reduce){html{scroll-behavior:auto}}