:root {
    --nav-background: #000000;
    --nav-text-color: #ffffff;
    --title-text-color: #ffffff;
    --content-background: rgba(0, 0, 0, 0.8);
    --content-text-color: #e2e2e2;
    --link-hover-color: #ff0077;
    --desc-text-color: #888888;
}
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    -webkit-touch-callout: none;
    -webkit-tap-highlight-color: transparent;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

html,
body {
    scroll-behavior: smooth;
}
html {
    -webkit-text-size-adjust: 100%;
    text-size-adjust: 100%;
}
body {
    overflow-x: hidden;
    -webkit-overflow-scrolling: touch;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    font-family: Inter, 'PingFang SC', 'Microsoft YaHei', '微软雅黑', system-ui, -apple-system, sans-serif;
}

a,
a:link,
a:visited,
a:hover,
a:active {
    color: inherit;
    outline: none;
    text-decoration: none;
}
a:hover,
a.active {
    color: var(--link-hover-color);
}
/* ===== 移动设备 (默认样式, <768px) ===== */

header {
    display: block;
    width: 100%;
    font-size: 14px;
    height: 60px;
    color: var(--nav-text-color);
    background-color: var(--nav-background);
}

header .container {
    max-width: 1500px;
    margin: 0 auto;
    padding: 0 25px;
    width: 100%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 100%;
}
header .logo {
    width: 200px;
}
header .logo img {
    width: 100%;
}
header nav {
    font-weight: bold;
}
main {
    display: block;
    width: 100%;
    padding: 20px 20px 50px;
    min-height: calc(100vh - 60px - 196px);
    color: var(--content-text-color);
    background-color: var(--content-background);
}
footer {
    display: block;
    text-align: center;
    width: 100%;
    font-size: 14px;
    padding: 40px 0;
    color: var(--nav-text-color);
    background-color: var(--nav-background);
}
footer nav {
    display: flex;
    flex-direction: column;
    gap: 28px;
}
footer nav a {
    line-height: 20px;
}
.back-top {
    position: fixed;
    right: 30px;
    bottom: 10px;
    z-index: 100;
    width: 32px;
    height: 32px;
    cursor: pointer;
    background: url('../assets/images/up.png') no-repeat;
    background-size: contain;
    opacity: 0;
    transition: all 0.3s ease;
}
.back-top:hover {
    background-image: url('../assets/images/up_hover.png');
}
.back-top.show {
    bottom: 30px;
    opacity: 1;
}
/* ===== 平板设备 (≥768px) ===== */
@media (min-width: 768px) {
    header {
        height: 80px;
        font-size: 16px;
    }
    header .logo {
        width: 280px;
    }
    main {
        min-height: calc(100vh - 80px - 160px);
    }
    footer {
        height: 160px;
        font-size: 18px;
    }
    footer nav {
        display: flex;
        flex-direction: row;
        justify-content: center;
        gap: 100px;
    }
    .back-top {
        right: 50px;
        bottom: 10px;
    }
    .back-top.show {
        bottom: 50px;
    }
}

/* ===== 电脑设备 (>=1280px) ===== */
@media (min-width: 1280px) {
    .back-top {
        width: 48px;
        height: 48px;
        right: 100px;
        bottom: 10px;
    }
    .back-top.show {
        bottom: 100px;
    }
}