body {
            font-family: Arial, sans-serif;
            background-color: #f4f4f4;
            padding: 10px;
            margin: 0;
        }
        h1 {
            text-align: center;
            color: #333;
        }
        button {
            padding: 10px 15px;
            background-color: #28a745;
            color: white;
            border: none;
            border-radius: 5px;
            cursor: pointer;
        }

        #task-manager {
            background: #fff;
            padding: 20px;
            margin: auto;
            width: 80%;
            max-width: 600px;
            box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
        }

        #task-form {
            margin-bottom: 20px;
        }

        #task-input {
            padding: 10px;
            width: 70%;
            margin-right: 10px;
        }

        #task-list {
            list-style-type: none;
            padding: 0;
        }

        #task-list li {
            background: #eee;
            padding: 10px;
            margin-bottom: 5px;
            border-radius: 5px;
        }

        /* Dark theme styles */
        body.dark-theme {
            background-color: #333;
            color: #fff;
        }

        .dark-theme #task-manager {
            background: #222;
            color: #fff;
        }

        .dark-theme #task-list li {
            background: #444;
        }

        .dark-theme #task-input {
            background: #333;
            color: #fff;
            border: 1px solid #555;
        }