body{background:#f4f4f4;font-family:Arial,sans-serif}.app{background:#fff;border-radius:5px;max-width:400px;margin:40px auto;padding:20px}.todo-input{gap:10px;display:flex}.todo-input input{flex:1;padding:8px}.todo-input button{padding:8px 12px}.todo-list{margin-top:20px;padding:0;list-style:none}.todo-item{justify-content:space-between;align-items:center;margin-bottom:8px;display:flex}.completed{color:gray;text-decoration:line-through}