body {
    font-family: 'Arial', sans-serif;
    line-height: 1.6;
    color: #333;
    margin: 0;
    padding: 0;
}

header {
    background-color: #fff;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    position: fixed;
    width: 100%;
    top: 0;
    z-index: 1000;
}

nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 5%;
}

.logo img {
    height: 40px;
}

nav ul {
    display: flex;
    list-style: none;
}

nav ul li {
    margin-right: 2rem;
}

nav ul li a {
    text-decoration: none;
    color: #333;
    font-weight: bold;
}

.login-btn {
    background-color: #007bff;
    color: white;
    border: none;
    padding: 0.5rem 1rem;
    border-radius: 5px;
    cursor: pointer;
}

main {
    margin-top: 60px; /* 为固定的header留出空间 */
}

.hero {
    background-size: cover;
    background-position: center;
    height: 500px;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    color: white;
}

.hero-content {
    background-color: rgba(0,0,0,0.5);
    padding: 2rem;
    border-radius: 10px;
}

.hero h1 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.cta-btn {
    background-color: #ff6b6b;
    color: white;
    border: none;
    padding: 1rem 2rem;
    font-size: 1.2rem;
    border-radius: 5px;
    cursor: pointer;
}

.features {
    display: flex;
    justify-content: space-around;
    padding: 4rem 5%;
    background-color: #f8f9fa;
}

.feature {
    text-align: center;
    max-width: 250px;
}

.feature img {
    width: 80px;
    margin-bottom: 1rem;
}

.courses {
    padding: 4rem 5%;
}

.course-list {
    display: flex;
    justify-content: space-between;
    flex-wrap: wrap;
}

.course {
    width: 30%;
    margin-bottom: 2rem;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    border-radius: 10px;
    overflow: hidden;
}

.course img {
    width: 100%;
    height: 200px;
    object-fit: cover;
}

.course h3, .course p {
    padding: 0 1rem;
}

footer {
    background-color: #333;
    color: white;
    padding: 2rem 5%;
}

.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.footer-content nav a {
    color: white;
    text-decoration: none;
    margin-right: 1rem;
}

.social-icons img {
    width: 30px;
    margin-left: 1rem;
}