/* =================================
           1. CSS 变量与全局样式
           ================================= */
:root {
    --primary-color: #007AFF;
    --background-color: #000000;
    --text-color: #FFFFFF;
    --secondary-text-color: #a1a1a6;
    --card-background-color: rgba(28, 28, 30, 0.7);
    --border-color: rgba(255, 255, 255, 0.1);
    --hover-background-color: rgba(255, 255, 255, 0.2);
    --border-radius: 5px;
    --transition-speed: 0.3s;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
    background-color: var(--background-color);
    color: var(--text-color);
    line-height: 1.6;
    overflow-x: hidden;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* =================================
           2. Header / 导航栏
           ================================= */
header {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    padding: 15px 0;
    z-index: 1000;
    background: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    /* 兼容 Safari */
    border-bottom: 1px solid var(--border-color);
}

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

.logo {
    font-size: 1.5rem;
    font-weight: bold;
    text-decoration: none;
    color: var(--text-color);
}

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

nav ul li {
    margin-left: 30px;
}

nav ul li a {
    text-decoration: none;
    color: var(--secondary-text-color);
    transition: color var(--transition-speed) ease;
}

nav ul li a:hover {
    color: var(--text-color);
}

.header-buttons .github-btn {
    text-decoration: none;
    padding: 8px 16px;
    border-radius: var(--border-radius);
    color: var(--text-color);
    border: 1px solid var(--border-color);
    transition: background-color var(--transition-speed) ease;
}

.header-buttons .github-btn:hover {
    background-color: var(--card-background-color);
}

/* =================================
           3. Hero / 主视觉区
           ================================= */
.hero {
    padding: 180px 0 120px;
    text-align: center;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: -50%;
    left: 50%;
    width: 800px;
    height: 800px;
    background: radial-gradient(circle, rgba(0, 122, 255, 0.2), transparent 60%);
    transform: translateX(-50%);
    z-index: -1;
    pointer-events: none;
}

.hero h1 {
    font-size: 3.5rem;
    margin-bottom: 20px;
    line-height: 1.2;
    font-weight: 600;
}

.hero p {
    font-size: 1.2rem;
    color: var(--secondary-text-color);
    max-width: 600px;
    margin: 0 auto 40px;
}

.cta-button {
    display: inline-block;
    background-color: var(--primary-color);
    color: var(--text-color);
    padding: 15px 30px;
    font-size: 1rem;
    font-weight: 500;
    text-decoration: none;
    border-radius: var(--border-radius);
    transition: background-color var(--transition-speed) ease;
}

.cta-button:hover {
    background-color: #0062cc;
    /* 略微加深的蓝色 */
}

/* =================================
           4. Features / 特性区
           ================================= */
.features {
    padding: 80px 0;
}

.features h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 60px;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 25px;
}

.feature-card {
    background-color: var(--card-background-color);
    padding: 30px;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    /* 优化点: 将 transform 和 box-shadow 替换为更微妙的 border-color 过渡 */
    transition: border-color var(--transition-speed) ease;
}

.feature-card:hover {
    /* 优化点: 悬停时仅高亮边框，效果更专业稳重 */
    border-color: var(--primary-color);
}

.feature-card h3 {
    font-size: 1.5rem;
    margin-bottom: 15px;
}

.feature-card p {
    color: var(--secondary-text-color);
}

/* =================================
           5. Download / 下载区
           ================================= */
.download {
    padding: 80px 0;
    text-align: center;
    background-color: var(--card-background-color);
    border-top: 1px solid var(--border-color);
    border-bottom: 1px solid var(--border-color);
}

.download h2 {
    font-size: 2.5rem;
    margin-bottom: 20px;
}

.download p {
    color: var(--secondary-text-color);
    margin-bottom: 40px;
}

.download-buttons {
    display: flex;
    justify-content: center;
    gap: 20px;
    flex-wrap: wrap;
}

.download-btn {
    display: inline-flex;
    align-items: center;
    background-color: rgba(255, 255, 255, 0.1);
    color: var(--text-color);
    padding: 12px 24px;
    text-decoration: none;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    transition: background-color var(--transition-speed) ease;
}

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

.download-btn svg {
    margin-right: 10px;
    width: 20px;
    height: 20px;
}

/* =================================
           6. Footer / 页脚
           ================================= */
footer {
    padding: 40px 0;
}

footer .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 20px;
}

.footer-links {
    list-style: none;
    display: flex;
    gap: 20px;
}

.footer-links a {
    color: var(--secondary-text-color);
    text-decoration: none;
    transition: color var(--transition-speed) ease;
}

.footer-links a:hover {
    color: var(--text-color);
}

.copyright {
    color: var(--secondary-text-color);
    font-size: 0.9rem;
}

/* =================================
           7. Responsive / 响应式布局
           ================================= */
@media (max-width: 768px) {
    header .container {
        flex-direction: column;
        gap: 15px;
    }

    nav ul {
        padding-top: 10px;
        flex-wrap: wrap;
        justify-content: center;
    }

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

    .hero p {
        font-size: 1.1rem;
    }

    footer .container {
        flex-direction: column;
        text-align: center;
    }
}