*{margin:0;padding:0;box-sizing:border-box}body{font-family:Segoe UI,Tahoma,Geneva,Verdana,sans-serif;background-color:#f5f5f5;color:#333}.app{min-height:100vh;padding:20px}.container{max-width:600px;margin:0 auto;background-color:#fff;border-radius:10px;box-shadow:0 2px 10px #0000001a;padding:30px}h1{text-align:center;color:#2c3e50;margin-bottom:30px;font-size:2rem}.add-task-form{display:flex;gap:10px;margin-bottom:30px}.task-input{flex:1;padding:12px 15px;border:2px solid #ddd;border-radius:5px;font-size:1rem;outline:none;transition:border-color .3s}.task-input:focus{border-color:#3498db}.add-button{padding:12px 20px;background-color:#3498db;color:#fff;border:none;border-radius:5px;cursor:pointer;font-size:1rem;transition:background-color .3s}.add-button:hover{background-color:#2980b9}.tasks-list{margin-top:20px}.task-item{display:flex;align-items:center;gap:10px;padding:15px;border-bottom:1px solid #eee;transition:background-color .3s}.task-item:hover{background-color:#f9f9f9}.task-item.completed{opacity:.7}.task-checkbox{width:18px;height:18px;cursor:pointer}.task-title{flex:1;font-size:1.1rem}.task-item.completed .task-title{text-decoration:line-through;color:#7f8c8d}.delete-button{padding:8px 15px;background-color:#e74c3c;color:#fff;border:none;border-radius:5px;cursor:pointer;font-size:.9rem;transition:background-color .3s}.delete-button:hover{background-color:#c0392b}.no-tasks{text-align:center;color:#7f8c8d;font-style:italic;padding:20px}@media (max-width: 600px){.container{margin:10px;padding:20px}.add-task-form{flex-direction:column}.task-item{flex-direction:column;align-items:flex-start}.task-item .task-title{margin:10px 0}}