/* Reset and base styles */
:root {
    --primary-color: #ff9000;
    --primary-hover: #ff6000;
    --text-color: #ffffff;
    --text-secondary: #cccccc;
    --background-dark: #000000;
    --background-light: #1b1b1b;
    --border-color: #2c2c2c;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
    background-color: var(--background-dark);
    color: var(--text-color);
    line-height: 1.6;
}

a {
    color: var(--primary-color);
    text-decoration: none;
    transition: color 0.3s ease;
}

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

/* Accessibility improvements */
:focus {
    outline: 3px solid var(--primary-color);
    outline-offset: 2px;
}

.skip-link {
    position: absolute;
    top: -40px;
    left: 0;
    background: var(--primary-color);
    color: white;
    padding: 8px;
    z-index: 100;
}

.skip-link:focus {
    top: 0;
}

/* Header styles */
header {
    background-color: var(--background-light);
    padding: 1rem 0;
    border-bottom: 1px solid var(--border-color);
}

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

.logo {
    font-size: 1.5rem;
    font-weight: bold;
}

.logo a {
    color: var(--primary-color);
    font-weight: bold;
}

.nav-links {
    display: flex;
    gap: 2rem;
    list-style: none;
}

.nav-links a {
    color: var(--text-color);
    font-weight: 500;
}

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

/* Main content */
main {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem;
}

/* Hero section */
.hero {
    text-align: center;
    padding: 4rem 2rem;
    background-color: #f8f9fa;
    border-radius: 8px;
    margin-bottom: 3rem;
}

.hero h1 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    color: var(--primary-color);
}

.hero p {
    color: var(--text-color);
}

/* Course categories */
.category-grid {
    display: flex;
    flex-wrap: wrap;
    gap: 2rem;
    justify-content: center;
    margin: 2rem 0;
}

.category-card {
    flex: 1 1 300px;
    max-width: 350px;
    padding: 1.5rem;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    background-color: white;
    transition: transform 0.3s;
}

.category-card:hover {
    transform: translateY(-5px);
}

.category-card h3 {
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.category-card ul {
    list-style-position: inside;
    margin-bottom: 1.5rem;
}

.category-card ul li {
    color: var(--text-color);
}

.btn {
    display: inline-block;
    padding: 0.8rem 1.5rem;
    border-radius: 4px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.3s ease;
    border: none;
    color: var(--text-color);
    background-color: var(--primary-color);
}

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

.btn-secondary {
    background-color: var(--background-light);
    color: var(--text-color);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover {
    /* Featured courses */
    .course-grid {
        display: flex;
        flex-wrap: wrap;
        gap: 2rem;
        margin-top: 2rem;
    }
}

/* Footer */
footer {
    background-color: var(--primary-color);
    color: white;
    padding: 3rem 1rem 1rem;
    margin-top: 4rem;
}

.footer-content {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-around;
    max-width: 1200px;
    margin: 0 auto;
    gap: 2rem;
}

.footer-section {
    flex: 1 1 250px;
}

.footer-section h4 {
    margin-bottom: 1rem;
    color: var(--primary-color);
}

.footer-section p {
    color: var(--text-secondary);
}

.footer-bottom {
    text-align: center;
    margin-top: 2rem;
    padding-top: 1rem;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

.footer-bottom p {
    color: var(--text-secondary);
}

/* Responsive design */
@media (max-width: 768px) {
    nav {
        flex-direction: column;
        gap: 1rem;
    }

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

    .hero {
        padding: 2rem 1rem;
    }

    .hero h1 {
        font-size: 2rem;
    }

    .category-card {
        flex: 1 1 100%;
    }
}

/* High contrast mode */
@media (prefers-contrast: high) {
    :root {
        --primary-color: #000000;
        --secondary-color: #0000EE;
        --accent-color: #EE0000;
        --text-color: #000000;
        --background-color: #FFFFFF;
    }
}

/* Reduced motion */
@media (prefers-reduced-motion: reduce) {
    * {
        animation: none !important;
        transition: none !important;
    }
}

/* Page title styles */
h1, h2, h3, h4 {
    color: var(--primary-color);
}

/* 固定底部订阅栏 */
.fixed-subscribe-bar {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background: linear-gradient(90deg, rgba(0, 0, 0, 0.95), rgba(255, 144, 0, 0.1));
    backdrop-filter: blur(10px);
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    z-index: 1000;
    box-shadow: 0 -4px 12px rgba(0, 0, 0, 0.2);
}

.subscribe-bar-content {
    display: flex;
    align-items: center;
    gap: 2rem;
    max-width: 1200px;
    margin: 0 auto;
    width: 100%;
}

.subscribe-bar-text {
    flex: 1;
}

.subscribe-bar-text h3 {
    color: var(--primary-color);
    font-size: 1.2rem;
    margin-bottom: 0.3rem;
}

.subscribe-bar-text p {
    color: var(--text-color);
    font-size: 0.9rem;
    opacity: 0.8;
}

.subscribe-bar-button {
    background-color: var(--primary-color);
    color: var(--text-color);
    padding: 0.8rem 2rem;
    border: none;
    border-radius: 30px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    text-transform: uppercase;
    white-space: nowrap;
}

.subscribe-bar-button:hover {
    background-color: var(--primary-hover);
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(255, 144, 0, 0.3);
}

.subscribe-bar-close {
    position: fixed;
    bottom: 80px;
    right: 20px;
    background: var(--primary-color);
    border: none;
    color: var(--text-color);
    font-size: 1.5rem;
    cursor: pointer;
    opacity: 0.9;
    transition: opacity 0.3s ease;
    padding: 0.5rem;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 30px;
    height: 30px;
    border-radius: 50%;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.2);
    z-index: 1001;
}

.subscribe-bar-close:hover {
    opacity: 1;
    background-color: var(--primary-hover);
}

@media (max-width: 768px) {
    .fixed-subscribe-bar {
        padding: 1rem;
    }

    .subscribe-bar-content {
        flex-direction: column;
        gap: 1rem;
        text-align: center;
    }

    .subscribe-bar-text h3 {
        font-size: 1.1rem;
    }

    .subscribe-bar-text p {
        font-size: 0.8rem;
    }

    .subscribe-bar-button {
        width: 100%;
        padding: 0.8rem 1rem;
    }
}

/* 模态窗口订阅栏样式 */
.modal-subscribe-bar {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background: linear-gradient(90deg, rgba(0, 0, 0, 0.95), rgba(255, 144, 0, 0.1));
    backdrop-filter: blur(10px);
    padding: 1rem 2rem;
    z-index: 1000;
    box-shadow: 0 -4px 12px rgba(0, 0, 0, 0.2);
}

.modal-subscribe-bar .subscribe-bar-content {
    display: flex;
    align-items: center;
    gap: 2rem;
    max-width: 1200px;
    margin: 0 auto;
    width: 100%;
}

.modal-subscribe-bar .subscribe-bar-text {
    flex: 1;
}

.modal-subscribe-bar .subscribe-bar-text h3 {
    color: var(--primary-color);
    font-size: 1.2rem;
    margin-bottom: 0.3rem;
}

.modal-subscribe-bar .subscribe-bar-text p {
    color: var(--text-color);
    font-size: 0.9rem;
    opacity: 0.8;
}

.modal-subscribe-bar .subscribe-bar-button {
    background-color: var(--primary-color);
    color: var(--text-color);
    padding: 0.8rem 2rem;
    border: none;
    border-radius: 30px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    text-transform: uppercase;
    white-space: nowrap;
}

.modal-subscribe-bar .subscribe-bar-button:hover {
    background-color: var(--primary-hover);
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(255, 144, 0, 0.3);
}

@media (max-width: 768px) {
    .modal-subscribe-bar {
        padding: 1rem;
    }

    .modal-subscribe-bar .subscribe-bar-content {
        flex-direction: column;
        gap: 1rem;
        text-align: center;
    }

    .modal-subscribe-bar .subscribe-bar-text h3 {
        font-size: 1.1rem;
    }

    .modal-subscribe-bar .subscribe-bar-text p {
        font-size: 0.8rem;
    }

    .modal-subscribe-bar .subscribe-bar-button {
        width: 100%;
        padding: 0.8rem 1rem;
    }
}