body { font-family: sans-serif; margin: 0; padding: 0; background: #f4f4f9; display: flex; flex-direction: column; min-height: 100vh; }
header { background: #333; color: #fff; padding: 1rem; text-align: center; }
main { flex: 1; padding: 20px; max-width: 800px; margin: auto; width: 100%; }
footer { background: #333; color: #fff; text-align: center; padding: 10px; }
.card { background: white; padding: 20px; border-radius: 8px; box-shadow: 0 2px 5px rgba(0,0,0,0.1); }