:root{--ink:#1d2421;--muted:#5f6b65;--line:#d7ddd9;--bg:#f7f8f6;--card:#fff;--accent:#24563f;--bad:#a3322a}
@media (prefers-color-scheme:dark){:root{--ink:#e8ece9;--muted:#a3ada8;--line:#38403c;--bg:#151917;--card:#1e2320;--accent:#7cc4a0;--bad:#f08a80}}
*{box-sizing:border-box}body{margin:0;min-height:100vh;display:grid;place-items:center;background:var(--bg);color:var(--ink);font:16px/1.6 system-ui,"Hiragino Sans","Noto Sans JP",sans-serif}
main{width:min(420px,100% - 32px);background:var(--card);border:1px solid var(--line);border-radius:14px;padding:32px 28px}
h1{margin:0 0 24px;font-size:22px}h1 span,label span,button span,p span{display:block;font-size:13px;font-weight:400;color:var(--muted)}
button span{color:inherit;opacity:.8}label{display:block;font-weight:600;margin:0 0 6px}
input{width:100%;font:inherit;font-size:18px;padding:12px 14px;border:1px solid var(--line);border-radius:10px;background:transparent;color:inherit;margin-bottom:16px}
input:focus{outline:2px solid var(--accent);outline-offset:1px}#code{letter-spacing:.3em;text-align:center}
button{width:100%;font:inherit;font-weight:600;padding:12px;border:0;border-radius:10px;background:var(--accent);color:var(--card);cursor:pointer;margin-top:4px}
button:disabled{opacity:.6;cursor:wait}button.link{background:none;color:var(--muted);font-weight:400}#choices button{margin-bottom:8px}
.google{display:block;text-align:center;margin-top:12px;padding:12px;border:1px solid var(--line);border-radius:10px;color:inherit;text-decoration:none;font-weight:600}.google span{display:block;font-size:13px;font-weight:400;color:var(--muted)}
#message{min-height:1.6em;margin:16px 0 0;color:var(--muted)}#message.bad{color:var(--bad)}