:root{--bg:#0d1117;--fg:#e6edf3;--ac:#58a6ff}
*{box-sizing:border-box}
body{background:var(--bg);color:var(--fg);font:15px/1.5 system-ui;margin:0;
display:flex;min-height:100vh;align-items:center;justify-content:center}
.card{background:#161b22;border:1px solid #30363d;border-radius:12px;padding:2rem;max-width:420px;width:90%}
h1{margin-top:0;font-size:1.3rem}
button{background:var(--ac);color:#000;border:0;border-radius:8px;padding:.6rem 1rem;font-weight:600;cursor:pointer}