/* 头部样式 */
header {
    background-color: white;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    position: sticky;
    top: 0;
    z-index: 100;
}

nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2rem;
    max-width: 1200px;
    margin: 0 auto;
}

.logo h1 {
    color: var(--primary-color);
    font-size: 1.8em;
    margin: 0;
}

.nav-links {
    display: flex;
    gap: 2rem;
}

.nav-links a {
    color: var(--text-color);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.3s;
}

.nav-links a:hover {
    color: var(--primary-color);
}

.nav-links a.active {
    color: var(--primary-color);
    font-weight: 600;
}

.auth-buttons {
    display: flex;
    gap: 1rem;
}

.login-btn, .signup-btn {
    padding: 0.5rem 1.5rem;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-weight: 500;
    transition: all 0.3s;
}

.login-btn {
    background-color: transparent;
    color: var(--primary-color);
    border: 1px solid var(--primary-color);
}

.login-btn:hover {
    background-color: var(--primary-color);
    color: white;
}

.signup-btn {
    background-color: var(--primary-color);
    color: white;
}

.signup-btn:hover {
    background-color: #357abd;
}

/* 响应式设计 */
@media (max-width: 768px) {
    nav {
        flex-direction: column;
        padding: 1rem;
    }

    .nav-links {
        flex-direction: column;
        align-items: center;
        gap: 1rem;
        margin: 1rem 0;
    }

    .auth-buttons {
        width: 100%;
        justify-content: center;
    }

    .login-btn, .signup-btn {
        width: 45%;
    }
}