body{font-family:Arial;background:#f3f4f6;margin:0}
header{background:#111827;color:white;padding:30px;text-align:center}
main{max-width:900px;margin:auto;padding:20px}
.card{background:white;padding:25px;margin:20px 0;border-radius:15px}
.hidden{display:none}
input,button{width:100%;padding:12px;margin:8px 0}
button{background:#2563eb;color:white;border:0;border-radius:8px}