body { font-family: Arial, sans-serif; margin: 0; background: #f5f7fb; color: #1f2937; }
header { background: #0f172a; color: white; padding: 20px; text-align: center; }
nav a { color: white; margin: 0 10px; text-decoration: none; }
main { max-width: 900px; margin: 40px auto; padding: 0 20px; }
.card { background: white; border-radius: 12px; padding: 28px; box-shadow: 0 8px 20px rgba(15,23,42,.08); }