/* ===== 页面头部 ===== */
.page-header {
    padding: 140px 0 80px;
    background: var(--bg-dark);
    text-align: center;
    color: white;
    position: relative;
    overflow: hidden;
}

.page-header::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: 
        radial-gradient(circle at 50% 30%, rgba(0, 136, 204, 0.2) 0%, transparent 50%);
}

.page-header .container {
    position: relative;
    z-index: 1;
}

.page-header h1 {
    font-size: 3rem;
    margin-bottom: 16px;
    font-weight: 800;
}

.page-header p {
    font-size: 1.25rem;
    opacity: 0.9;
}

/* ===== 下载平台选择 ===== */
.download-platforms {
    padding: 80px 0;
    background-color: var(--bg-secondary);
}

.platform-tabs {
    display: flex;
    justify-content: center;
    gap: 12px;
    margin-bottom: 60px;
}

.tab-btn {
    padding: 12px 32px;
    border: 2px solid var(--border-color);
    background-color: var(--bg-color);
    color: var(--text-primary);
    font-size: 1rem;
    font-weight: 600;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: var(--transition);
}

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

.tab-btn.active {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    border-color: transparent;
    color: white;
    box-shadow: 0 4px 15px rgba(0, 136, 204, 0.3);
}

.platform-content {
    display: none;
}

.platform-content.active {
    display: block;
    animation: fadeInUp 0.5s ease;
}

@keyframes fadeInUp {
    from { 
        opacity: 0; 
        transform: translateY(20px); 
    }
    to { 
        opacity: 1; 
        transform: translateY(0); 
    }
}

.platform-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 32px;
}

.platform-card {
    background-color: var(--bg-color);
    border-radius: var(--radius-xl);
    padding: 48px 40px;
    text-align: center;
    transition: var(--transition);
    border: 2px solid transparent;
    box-shadow: var(--shadow-sm);
}

.platform-card:hover {
    border-color: var(--primary-color);
    transform: translateY(-8px);
    box-shadow: var(--shadow-xl);
}

.platform-icon {
    width: 100px;
    height: 100px;
    margin: 0 auto 32px;
    border-radius: 24px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.platform-icon svg {
    width: 56px;
    height: 56px;
    color: white;
}

.platform-icon.android {
    background: linear-gradient(135deg, #3ddc84, #00c853);
    box-shadow: 0 8px 20px rgba(61, 220, 132, 0.3);
}

.platform-icon.ios {
    background: linear-gradient(135deg, #5e5ce6, #3634a3);
    box-shadow: 0 8px 20px rgba(94, 92, 230, 0.3);
}

.platform-icon.windows {
    background: linear-gradient(135deg, #0078d4, #005a9e);
    box-shadow: 0 8px 20px rgba(0, 120, 212, 0.3);
}

.platform-icon.macos {
    background: linear-gradient(135deg, #ff2d55, #d81b60);
    box-shadow: 0 8px 20px rgba(255, 45, 85, 0.3);
}

.platform-icon.linux {
    background: linear-gradient(135deg, #333333, #1a1a1a);
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.3);
}

.platform-card h3 {
    font-size: 2rem;
    margin-bottom: 20px;
    color: var(--text-primary);
    font-weight: 800;
}

.version-info {
    display: flex;
    justify-content: center;
    gap: 16px;
    margin-bottom: 24px;
}

.version, .size {
    padding: 8px 20px;
    background-color: var(--bg-secondary);
    border-radius: var(--radius-xl);
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--text-secondary);
}

.requirements {
    list-style: none;
    margin-bottom: 32px;
    text-align: left;
}

.requirements li {
    padding: 12px 0;
    color: var(--text-secondary);
    position: relative;
    padding-left: 32px;
    line-height: 1.6;
}

.requirements li::before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--primary-color);
    font-weight: bold;
    font-size: 1.2rem;
}

.download-btn {
    width: 100%;
    padding: 18px 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 12px;
    margin-bottom: 16px;
    font-size: 1.125rem;
}

.download-btn svg {
    width: 24px;
    height: 24px;
}

.download-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(0, 136, 204, 0.4);
}

.download-btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none;
}

.secondary-link {
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.95rem;
    font-weight: 500;
    transition: var(--transition);
}

.secondary-link:hover {
    color: var(--primary-color);
}

/* ===== 系统要求 ===== */
.system-requirements {
    padding: 100px 0;
    background-color: var(--bg-color);
}

.system-requirements h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 60px;
    color: var(--text-primary);
    font-weight: 800;
}

.requirements-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 32px;
}

.requirement-item {
    background-color: var(--bg-secondary);
    padding: 40px 32px;
    border-radius: var(--radius-xl);
    text-align: center;
    transition: var(--transition);
    border: 2px solid transparent;
}

.requirement-item:hover {
    transform: translateY(-5px);
    border-color: var(--primary-color);
    box-shadow: var(--shadow-md);
}

.requirement-item h3 {
    font-size: 1.25rem;
    margin-bottom: 12px;
    color: var(--text-primary);
    font-weight: 700;
}

.requirement-item p {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

/* ===== 扫码下载 ===== */
.qr-download {
    padding: 100px 0;
    background-color: var(--bg-secondary);
}

.qr-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 80px;
    align-items: center;
    max-width: 1000px;
    margin: 0 auto;
}

.qr-code {
    width: 280px;
    height: 280px;
    background-color: var(--bg-color);
    border-radius: 24px;
    padding: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto;
    box-shadow: var(--shadow-xl);
}

.qr-code svg {
    width: 100%;
    height: 100%;
    color: var(--text-primary);
}

.qr-info h3 {
    font-size: 2.25rem;
    margin-bottom: 16px;
    color: var(--text-primary);
    font-weight: 800;
}

.qr-info p {
    color: var(--text-secondary);
    margin-bottom: 32px;
    font-size: 1.125rem;
    line-height: 1.8;
}

.qr-links {
    display: flex;
    gap: 16px;
}

.qr-link {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 14px 28px;
    background-color: var(--bg-color);
    border-radius: 12px;
    text-decoration: none;
    color: var(--text-primary);
    font-weight: 600;
    transition: var(--transition);
    box-shadow: var(--shadow-sm);
}

.qr-link:hover {
    background-color: var(--primary-color);
    color: white;
    transform: translateY(-2px);
    box-shadow: 0 8px 20px rgba(0, 136, 204, 0.3);
}

.qr-link svg {
    width: 24px;
    height: 24px;
}

/* ===== 安装指南 ===== */
.install-guide {
    padding: 100px 0;
    background-color: var(--bg-color);
}

.install-guide h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 80px;
    color: var(--text-primary);
    font-weight: 800;
}

.guide-steps {
    max-width: 900px;
    margin: 0 auto;
}

.guide-step {
    display: flex;
    gap: 40px;
    margin-bottom: 48px;
    align-items: flex-start;
}

.step-number {
    width: 72px;
    height: 72px;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    border-radius: 20px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    font-weight: 800;
    color: white;
    flex-shrink: 0;
    box-shadow: 0 8px 20px rgba(0, 136, 204, 0.3);
}

.step-content h3 {
    font-size: 1.5rem;
    margin-bottom: 12px;
    color: var(--text-primary);
    font-weight: 700;
}

.step-content p {
    color: var(--text-secondary);
    line-height: 1.8;
    font-size: 1.125rem;
}

/* ===== 响应式设计 ===== */
@media (max-width: 1024px) {
    .qr-content {
        grid-template-columns: 1fr;
        text-align: center;
        gap: 48px;
    }
    
    .qr-links {
        justify-content: center;
    }
    
    .platform-grid {
        grid-template-columns: 1fr;
    }
    
    .guide-step {
        flex-direction: column;
        align-items: center;
        text-align: center;
    }
}

@media (max-width: 640px) {
    .page-header {
        padding: 120px 0 60px;
    }
    
    .page-header h1 {
        font-size: 2rem;
    }
    
    .page-header p {
        font-size: 1rem;
    }
    
    .platform-tabs {
        flex-direction: column;
        gap: 8px;
    }
    
    .tab-btn {
        width: 100%;
    }
    
    .qr-code {
        width: 240px;
        height: 240px;
    }
    
    .requirements-grid {
        grid-template-columns: 1fr;
    }
    
    .platform-card {
        padding: 40px 32px;
    }
    
    .platform-icon {
        width: 80px;
        height: 80px;
    }
    
    .platform-icon svg {
        width: 44px;
        height: 44px;
    }
    
    .platform-card h3 {
        font-size: 1.5rem;
    }
}