body{font-family:Arial;margin:0}header{padding:20px;background:#222;color:#fff}section{max-width:900px;margin:20px auto;padding:20px}article{padding:15px;margin:10px 0;border:1px solid #aaa}form{display:flex;flex-direction:column;gap:10px}input,textarea,button{padding:8px}.dark{background:#222;color:#fff;min-height:100vh}