/* Keystone History Lab · interactive lessons. System fonts only, no external requests. */
[hidden]{display:none!important}
:root{--navy:#1d3557;--teal:#23807a;--teal-d:#1b6560;--gold:#e9c46a;--ink:#1f2933;--muted:#52606d;--bg:#f7f8fa;--card:#fff;--line:#dde2e8;--warn:#9a3412}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;font-family:system-ui,-apple-system,"Segoe UI",Roboto,"Noto Sans",Arial,sans-serif;color:var(--ink);background:var(--bg);line-height:1.55;font-size:17px}
a{color:var(--teal-d)}a:hover{color:var(--navy)}
.wrap{max-width:1080px;margin:0 auto;padding:0 20px}
.skip{position:absolute;left:-999px}.skip:focus{left:8px;top:8px;background:#fff;padding:6px 10px;z-index:9}
header.site{background:var(--navy);color:#fff}
header.site .wrap{display:flex;align-items:center;gap:20px;min-height:64px;flex-wrap:wrap}
.logo{display:flex;align-items:center;gap:10px;color:#fff;text-decoration:none;font-weight:700;font-size:19px;letter-spacing:.2px}
.logo svg{flex:none}
.logo:hover{color:#fff}
nav.main{margin-left:auto;display:flex;gap:6px;flex-wrap:wrap}
nav.main a{color:#e8eef5;text-decoration:none;padding:8px 12px;border-radius:8px;font-size:16px}
nav.main a:hover,nav.main a[aria-current]{background:rgba(255,255,255,.12);color:#fff}
nav.main a.code{background:var(--gold);color:var(--navy);font-weight:700}
main{display:block}
.hero{background:linear-gradient(135deg,#1d3557 0%,#23807a 100%);color:#fff;padding:56px 0 64px}
.hero h1{font-size:42px;line-height:1.15;margin:0 0 14px;max-width:760px}
.hero p.lead{font-size:20px;max-width:680px;margin:0 0 26px;color:#e6f2f1}
.btn{display:inline-block;background:var(--teal);color:#fff;text-decoration:none;font-weight:700;padding:11px 20px;border-radius:10px;border:0;font:inherit;font-weight:700;cursor:pointer;line-height:1.3}
.btn:hover{background:var(--teal-d);color:#fff}
.btn.light{background:#fff;color:var(--navy)}.btn.light:hover{background:#eef3f8;color:var(--navy)}
.btn.ghost{background:transparent;color:#fff;box-shadow:inset 0 0 0 2px rgba(255,255,255,.7)}
.btn.soon,.btn[disabled]{background:#cfd6de;color:#3e4c59;cursor:not-allowed}
.btn.small{padding:7px 13px;font-size:15px}
.btns{display:flex;gap:12px;flex-wrap:wrap}
section{padding:44px 0}
section.alt{background:#fff;border-top:1px solid var(--line);border-bottom:1px solid var(--line)}
h2{font-size:28px;margin:0 0 10px;color:var(--navy)}
h3{margin:0 0 6px;color:var(--navy)}
.sub{color:var(--muted);margin:0 0 22px;max-width:720px}
.grid{display:grid;gap:18px;grid-template-columns:repeat(auto-fill,minmax(300px,1fr))}
.grid.three{grid-template-columns:repeat(auto-fit,minmax(240px,1fr))}
.card{background:var(--card);border:1px solid var(--line);border-radius:14px;padding:20px}
.lesson{display:flex;flex-direction:column;padding:0;overflow:hidden}
.lesson img{width:100%;aspect-ratio:16/9;object-fit:cover;background:#e4e8ee;display:block}
.lesson .body{padding:16px 18px 18px;display:flex;flex-direction:column;gap:6px;flex:1}
.lesson h3{font-size:20px}
.meta{font-size:14px;color:var(--muted)}
.tag{display:inline-block;font-size:13px;background:#e6f2f1;color:var(--teal-d);border-radius:999px;padding:2px 10px;margin-right:6px;font-weight:600}
.lesson p{margin:0;font-size:16px}
.lesson .pv{font-size:14px;color:var(--muted)}
.lesson .actions{margin-top:auto;padding-top:10px}
.steps{counter-reset:s;list-style:none;padding:0;margin:0;display:grid;gap:14px}
.steps li{counter-increment:s;position:relative;padding:14px 16px 14px 58px;background:#fff;border:1px solid var(--line);border-radius:12px}
.steps li::before{content:counter(s);position:absolute;left:16px;top:13px;width:30px;height:30px;border-radius:50%;background:var(--navy);color:#fff;font-weight:700;display:grid;place-items:center}
.note{background:#fff8e6;border:1px solid #f1d58a;border-radius:12px;padding:14px 16px}
.draft{background:#fff1f0;border:1px solid #f5b5ae;color:#7f1d1d;border-radius:12px;padding:12px 16px;font-weight:600}
.price{font-size:44px;font-weight:800;color:var(--navy);margin:6px 0}
.pill{display:inline-block;padding:4px 12px;border-radius:999px;font-weight:700;font-size:14px;background:#e6f2f1;color:var(--teal-d)}
.pill.soon{background:#fff1d6;color:#8a5a00}
code,.mono{font-family:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;font-size:.92em;background:#eef1f5;padding:1px 6px;border-radius:5px}
.prose{max-width:760px}
.prose h2{margin-top:30px}
footer.site{background:#13263f;color:#c9d4e0;padding:28px 0;font-size:15px;margin-top:0}
footer.site a{color:#e8eef5}
footer.site .wrap{display:flex;gap:18px;flex-wrap:wrap;align-items:center}
footer.site nav{display:flex;gap:16px;flex-wrap:wrap;margin-left:auto}
input.code,input.text{font:inherit;font-size:18px;padding:10px 12px;border:2px solid #b8c2cc;border-radius:10px;background:#fff;width:100%}
input.code{text-transform:uppercase;letter-spacing:4px;text-align:center;font-weight:700;max-width:240px}
input:focus{outline:3px solid #9fd3cf;border-color:var(--teal)}
label{display:block;font-weight:700;margin:14px 0 6px}
.err{color:#b42318;font-weight:700;min-height:1.3em;margin:8px 0 0}
.ok{color:var(--teal-d);font-weight:700}
.narrow{max-width:560px;margin:40px auto}
body.msg{background:var(--bg);padding:20px}
/* play page */
body.play{display:flex;flex-direction:column;min-height:100vh}
.bar{background:#fff;border-bottom:1px solid var(--line)}
.bar .wrap{max-width:none;display:flex;align-items:center;gap:12px;min-height:56px;flex-wrap:wrap;padding:6px 16px}
.bar h1{font-size:19px;margin:0;color:var(--navy)}
.bar .grow{flex:1}
.timer{font-variant-numeric:tabular-nums;font-weight:800;padding:5px 12px;border-radius:999px;background:#e6f2f1;color:var(--teal-d)}
.timer.low{background:#fff1d6;color:#8a5a00}
.timer.full{background:var(--navy);color:#fff}
.stage{flex:1;position:relative;background:#0f1b2b;min-height:420px}
.stage iframe{position:absolute;inset:0;width:100%;height:100%;border:0;background:#fff}
.lock{position:absolute;inset:0;display:none;align-items:center;justify-content:center;background:rgba(15,27,43,.92);padding:20px;z-index:3}
.lock.on{display:flex}
.lock .card{max-width:520px;width:100%;text-align:center}
.lock h2{margin-top:0}
.codeform{display:flex;gap:10px;justify-content:center;flex-wrap:wrap;align-items:center;margin-top:8px}
.codeform input{max-width:220px}
.drawer{display:none;background:#f0f6f6;border-bottom:1px solid var(--line);padding:12px 16px}
.drawer.on{display:block}
.banner{background:#e6f2f1;border:1px solid #b8dcd8;border-radius:12px;padding:12px 16px;margin:0 0 18px}
@media (max-width:640px){.hero h1{font-size:32px}.hero{padding:40px 0}nav.main{margin-left:0}body{font-size:16px}}
body.play main{flex:1;display:flex;flex-direction:column;min-height:calc(100vh - 64px)}
#lessonView:not([hidden]){display:flex;flex-direction:column;flex:1}