/* 基本重置和样式 */
* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
    line-height: 1.6;
    color: #333;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    background-color: #f4f4f4;
}

header, footer {
    background-color: #333;
    color: #fff;
    padding: 1rem;
    text-align: center;
}

header h1 {
    margin-bottom: 0.5rem;
}

nav#main-nav a {
    color: #fff;
    text-decoration: none;
    margin: 0 0.8rem;
    padding: 0.3rem 0.5rem;
    border-radius: 4px;
    transition: background-color 0.2s ease;
}

nav#main-nav a:hover,
nav#main-nav a.active { /* 活动链接样式 */
    background-color: #555;
}

main#app {
    flex-grow: 1; /* 让 main 区域填充剩余空间 */
    padding: 2rem;
    background-color: #fff;
    max-width: 900px;
    margin: 1rem auto; /* 居中并添加边距 */
    border-radius: 5px;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

/* 页面内容样式 */
.page-content {
    animation: fadeIn 0.5s ease-in-out;
}

.page-content h2 {
    margin-bottom: 1rem;
    color: #0056b3;
}

.loading, .error-message {
    font-style: italic;
    color: #777;
    text-align: center;
    padding: 2rem;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}