body{font-family:sans-serif;padding:24px}.app{max-width:500px}h1{margin-bottom:24px}.section{border:1px solid #ddd;border-radius:6px;padding:16px;margin-bottom:16px}h2{margin:0 0 12px;font-size:1rem;color:#555}button{margin-right:8px;padding:6px 14px;border:1px solid #aaa;border-radius:4px;cursor:pointer;background:#f5f5f5}button:hover:not(:disabled){background:#e0e0e0}button:disabled{opacity:.5;cursor:not-allowed}input{padding:6px 10px;border:1px solid #aaa;border-radius:4px;width:100%;box-sizing:border-box;margin-bottom:8px}.ok{color:green}.error{color:red}