Untitled

### HTML (index.html)
```html
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>To-Do List</title>
    <link rel="stylesheet" href="styles.css">
</head>
<body>
    <div class="container">
        <h1>To-Do List</h1>
        <input type="text" id="taskInput" placeholder="Add a new task...">
        <button onclick="addTask()">Add Task</button>
        <ul id="taskList"></ul>
    </div>
    <script src="script.js"></script>
</body>
</html>
```

### CSS (styles.css)
```css
body {
    font-family: Arial, sans-serif;
    background-color: #f4f4f4;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
}

.container {
    background: white;
    padding: 20px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
    border-radius: 8px;
    width: 300px;
    text-align: center;
}

input[type="text"] {
    width: calc(100% - 22px);
    padding: 10px;
    margin-bottom: 10px;
    border: 1px solid #ddd;
    border-radius: 4px;
}

button {
    padding: 10px;
    background: #28a745;
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
}

button:hover {
    background: #218838;
}

ul {
    list-style-type: none;
    padding: 0;
}

li {
    background: #f9f9f9;
    padding: 10px;
    margin-bottom: 5px;
    border-radius: 4px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

li.completed {
    text-decoration: line-through;
    color: #888;
}
```

### JavaScript (script.js)
```javascript
function addTask() {
    const taskInput = document.getElementById('taskInput');
    const taskText = taskInput.value.trim();

    if (taskText === '') {
        alert('Please enter a task.');
        return;
    }

    const taskList = document.getElementById('taskList');
    const listItem = document.createElement('li');
    listItem.textContent = taskText;

    const deleteButton = document.createElement('button');
    deleteButton.textContent = 'Delete';
    deleteButton.onclick = function () {
        taskList.removeChild(listItem);
    };

    listItem.appendChild(deleteButton);
    taskList.appendChild(listItem);

    listItem.onclick = function () {
        listItem.classList.toggle('completed');
    };

    taskInput.value = '';
}
```
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