body {
    font-family: 'Microsoft YaHei', sans-serif;
    margin: 0;
    padding: 20px;
    background-color: transparent;
}

.container {
    max-width: 800px;
    margin: 0 auto;
    background-color: white;
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

h1 {
    text-align: center;
    color: #333;
    margin-bottom: 30px;
}

.exercise {
    margin-bottom: 30px;
    padding: 20px;
    border: 1px solid #eee;
    border-radius: 5px;
}

h2 {
    color: #444;
    font-size: 1.2em;
    margin-bottom: 15px;
}

.code-box {
    background-color: #f8f9fa;
    padding: 15px;
    border-radius: 5px;
    font-size: 16px;
    line-height: 1.5;
}

@media screen and (max-width: 600px) {
    .container {
        padding: 10px;
    }
    
    .exercise {
        padding: 10px;
    }
}

.btn {
    padding: 8px 16px;
    background-color: #4CAF50;
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-size: 14px;
}

.btn:hover {
    background-color: #45a049;
}