html, body {
    height: 100%;
    margin: 0;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: #333;
}
body {
    display: flex;
    flex-direction: column;
    background-color: #f0f2f5; /* Lighter background */
}
header {
    background-color: #003366; /* 深蓝色 */
    color: #fff;
    padding: 10px 0;
    text-align: center;
    position: relative;
}
header h1 {
    margin: 0;
    font-size: 28px;
}
header .login-btn {
    position: absolute;
    right: 20px;
    top: 50%;
    transform: translateY(-50%);
    background-color: #0056b3;
    color: white;
    padding: 8px 15px;
    border-radius: 5px;
    text-decoration: none;
    font-size: 14px;
    transition: background-color 0.3s ease;
}
header .login-btn:hover {
    background-color: #004080;
}
.main-nav {
    display: flex;
    justify-content: center;
    gap: 20px;
    margin-top: 10px;
}
.main-nav a {
    color: white;
    text-decoration: none;
    padding: 5px 15px;
    border-radius: 5px;
    transition: background-color 0.3s ease;
}
.main-nav a:hover {
    background-color: #0056b3;
}
nav {
    border-bottom: 1px solid #002244;
    padding: 10px 0;
}
nav ul {
    list-style-type: none;
    padding: 0;
    margin: 0;
    text-align: center;
}
nav ul li {
    display: inline;
    margin: 0 15px;
}
nav ul li a {
    text-decoration: none;
    color: #fff;
    padding: 10px 0;
    display: inline-block;
    font-weight: 500;
    transition: color 0.3s ease;
}
nav ul li a:hover {
    color: #a0c0e0;
}
.container {
    width: 98%; /* Slightly wider */
    max-width: 1920px; /* Max width for larger screens */
    margin: 20px auto;
    padding: 25px; /* More padding */
    background-color: #ffffff;
    border-radius: 10px; /* More rounded corners */
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08); /* Softer, larger shadow */
    flex-grow: 1; /* Let content area fill remaining space */
}
footer {
    text-align: center;
    padding: 20px 0;
    color: #fff;
    background-color: #003366; /* 深蓝色 */
    height: 80px; /* Adjusted height */
    display: flex;
    align-items: center;
    justify-content: center;
    margin-top: auto; /* Push footer to the bottom */
    font-size: 14px;
}