/*
 * Shared styles for /learn/ pages.
 *
 * The rest of the site inlines its CSS, which was fine at five hand-written
 * pages and stops being fine somewhere around ten. New pages link this instead
 * of carrying their own copy, so a palette change is one edit rather than one
 * per file. Values match index.html's :root exactly — if that changes, change
 * it here too.
 */
:root{
  --bg:#ffffff; --card:#f6f8fa; --border:#d5dbe3; --border-soft:#e7ebf0;
  --text:#12161c; --muted:#586070; --dim:#69707e;
  --primary:#2563eb; --primary-dark:#1d4ed8; --accent:#1d4ed8;
  --success:#0f7a4f; --warn:#9a6100;
}
*{box-sizing:border-box}
body{margin:0;background:var(--bg);color:var(--text);line-height:1.6;
     font-family:-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,Helvetica,Arial,sans-serif}
a{color:var(--accent)}
.wrap{max-width:820px;margin:0 auto;padding:0 24px}

header{position:sticky;top:0;z-index:10;background:rgba(255,255,255,.88);backdrop-filter:blur(8px);
       border-bottom:1px solid var(--border-soft)}
nav.top{display:flex;align-items:center;justify-content:space-between;gap:16px;
        padding:16px 24px;max-width:1080px;margin:0 auto}
.brand{display:flex;align-items:center;gap:10px;font-weight:700;font-size:16px;text-decoration:none;color:var(--text)}
.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;padding:10px 18px;border-radius:10px;
     font-size:14px;font-weight:600;text-decoration:none;border:1px solid transparent;cursor:pointer}
.btn-primary{background:var(--primary);color:#fff}
.btn-primary:hover{background:var(--primary-dark)}
.btn-ghost{border-color:var(--border);color:var(--text);background:transparent}

.crumbs{font-size:13px;color:var(--dim);margin:28px 0 0}
.crumbs a{color:var(--muted);text-decoration:none}
.crumbs a:hover{text-decoration:underline}

h1{font-size:38px;line-height:1.15;letter-spacing:-.9px;margin:14px 0 16px}
h2{font-size:24px;line-height:1.25;letter-spacing:-.3px;margin:44px 0 12px;scroll-margin-top:80px}
h3{font-size:17px;margin:28px 0 8px}
p{margin:0 0 16px}
.lede{font-size:18px;color:var(--muted);margin-bottom:28px}
ul,ol{margin:0 0 16px;padding-left:22px}
li{margin:0 0 8px}
code{font-family:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;font-size:.9em;
     background:var(--card);border:1px solid var(--border-soft);border-radius:5px;padding:1px 5px;
     /* Long API names like Intl.DateTimeFormat().resolvedOptions().timeZone
        have no break opportunity and pushed the page wider than a phone. */
     overflow-wrap:anywhere}
/* No rule existed for pre, so a block with one long line pushed the whole
   PAGE wider than the phone rather than scrolling inside itself — measured at
   360px: a 703px code block against a 360px viewport. The code rule above
   cannot help here, because white-space:pre does not wrap. */
pre{overflow-x:auto;max-width:100%}

strong{color:var(--text)}
.muted{color:var(--muted)}

.toc{border:1px solid var(--border);background:var(--card);border-radius:12px;padding:18px 22px;margin:0 0 36px}
.toc h4{margin:0 0 10px;font-size:13px;text-transform:uppercase;letter-spacing:.08em;color:var(--dim)}
.toc ol{margin:0;padding-left:20px;font-size:14px}
.toc li{margin:0 0 6px}
.toc a{color:var(--muted);text-decoration:none}
.toc a:hover{color:var(--text);text-decoration:underline}

.callout{border:1px solid var(--border);background:var(--card);border-radius:12px;padding:18px 22px;margin:26px 0}
.callout p:last-child{margin-bottom:0}
.callout.tip{border-color:color-mix(in srgb, var(--primary) 40%, var(--border))}
.callout.warn{border-color:color-mix(in srgb, var(--warn) 40%, var(--border))}
.callout h4{margin:0 0 8px;font-size:15px}

table{width:100%;border-collapse:collapse;margin:0 0 20px;font-size:14px;display:block;overflow-x:auto}
th,td{text-align:left;padding:10px 14px;border-bottom:1px solid var(--border-soft);vertical-align:top}
th{color:var(--dim);font-weight:600;font-size:12px;text-transform:uppercase;letter-spacing:.06em;white-space:nowrap}

.next{display:grid;gap:12px;grid-template-columns:repeat(auto-fit,minmax(240px,1fr));margin:36px 0 10px}
.next a{display:block;border:1px solid var(--border);background:var(--card);border-radius:12px;
        padding:16px 18px;text-decoration:none;color:var(--text)}
.next a:hover{border-color:var(--primary)}
.next b{display:block;font-size:15px;margin-bottom:4px}
.next span{color:var(--muted);font-size:13px}

.cta{border:1px solid var(--border);background:var(--card);border-radius:14px;padding:26px;margin:44px 0 20px}
.cta h2{margin:0 0 8px;font-size:21px}
.cta p{color:var(--muted);font-size:15px}

footer{border-top:1px solid var(--border-soft);padding:32px 24px;margin-top:56px;
       text-align:center;color:var(--dim);font-size:13px}
footer a{color:var(--muted)}
.footer-links{display:flex;flex-wrap:wrap;gap:8px 22px;justify-content:center;margin:0 0 14px}

@media (max-width:640px){
  h1{font-size:29px}
  h2{font-size:21px}
  nav.top{padding:14px 16px}
  .wrap{padding:0 16px}
}