:root{--bg:#f6f7f9;--card:#fff;--ink:#16181d;--line:#e3e6ea;--bad:#b91c1c;--acc:#1d4ed8}
@media (prefers-color-scheme:dark){:root{--bg:#0f1115;--card:#171a21;--ink:#e8eaee;--line:#262b35;--bad:#f87171;--acc:#60a5fa}}
*{box-sizing:border-box}
body{margin:0;min-height:100vh;display:flex;align-items:center;justify-content:center;background:var(--bg);color:var(--ink);font:15px/1.5 system-ui,-apple-system,"Segoe UI",sans-serif}
#gate{width:min(360px,calc(100% - 32px));background:var(--card);border:1px solid var(--line);border-radius:12px;padding:28px 24px;text-align:center}
h1{font-size:18px;margin:0 0 18px}
button{width:100%;padding:11px 14px;font:inherit;font-weight:600;color:#fff;background:var(--acc);border:0;border-radius:8px;cursor:pointer}
button.off{opacity:.5;pointer-events:none}
#gateError{color:var(--bad);margin:0 0 14px}