body {
            font-family: Arial, sans-serif;
            background-color: #f4f4f4;
            display: flex;
            justify-content: center;
            align-items: center;
            height: 100vh;
            margin: 0;
        }
        .container {
            background-color: white;
            padding: 20px;
            border-radius: 8px;
            box-shadow: 0 0 10px rgba(0,0,0,0.1);
            width: 400px;
            max-width: 90%;
        }
        h1 {
            text-align: center;
            color: #333;
        }
        .input-container {
            display: flex;
            margin-bottom: 20px;
        }
        #todo-input {
            flex: 1;
            padding: 10px;
            border: 1px solid #ddd;
            border-radius: 4px 0 0 4px;
            outline: none;
        }
        #add-btn {
            padding: 10px 15px;
            background-color: #28a745;
            color: white;
            border: none;
            border-radius: 0 4px 4px 0;
            cursor: pointer;
        }
        #add-btn:hover {
            background-color: #218838;
        }
        ul {
            list-style: none;
            padding: 0;
        }
        li {
            display: flex;
            justify-content: space-between;
            align-items: center;
            padding: 10px;
            border-bottom: 1px solid #eee;
        }
        li.done span {
            text-decoration: line-through;
            color: #888;
        }
        .checkbox {
            margin-right: 10px;
        }
        .delete-btn {
            background-color: #dc3545;
            color: white;
            border: none;
            border-radius: 4px;
            padding: 5px 10px;
            cursor: pointer;
        }
        .delete-btn:hover {
            background-color: #c82333;
        }