body{font-family:Arial,sans-serif;margin:0;padding:20px;background-color:#f4f4f4}.app{max-width:500px;margin:0 auto;background:#fff;padding:20px;border-radius:8px;box-shadow:0 2px 4px #0000001a}h1{text-align:center;color:#333}.input-container{display:flex;margin-bottom:20px}input{flex:1;padding:10px;border:1px solid #ddd;border-radius:4px;font-size:16px}button{padding:10px 15px;background-color:#007bff;color:#fff;border:none;border-radius:4px;cursor:pointer;margin-left:10px}button:hover{background-color:#0056b3}.todo-list{list-style:none;padding:0}.todo-list li{display:flex;justify-content:space-between;align-items:center;padding:10px;border-bottom:1px solid #eee}.todo-list li.completed span{text-decoration:line-through;color:#888}.todo-list li button{background-color:#dc3545}.todo-list li button:hover{background-color:#c82333}