body{font-family:Arial;margin:0;background:#f4f6f8}header{background:#1f2937;color:#fff;padding:20px}nav a{color:#fff;margin-right:18px;text-decoration:none}main{max-width:1000px;margin:auto;padding:30px}.card{background:#fff;padding:20px;margin:20px 0}footer{background:#222;color:#fff;padding:20px;text-align:center}