:root {
    /* 极简基底：大留白 */
    --bg-base: #ffffff;
    --bg-alt: #fbfbfb;

    /* 文字颜色 */
    --text-primary: #000000;
    --text-secondary: #555555;
    --text-tertiary: #999999;

    /* 强调色：黑为主，羁绊红为点缀 */
    --brand-main: #000000;
    --brand-accent: #9e1a1a;

    --border-light: #ececec;

    /* 字体排版 */
    --font-display: -apple-system, BlinkMacSystemFont, "SF Pro Display", "Helvetica Neue", "PingFang SC", sans-serif;
    --font-body: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Helvetica Neue", "PingFang SC", sans-serif;
    --font-serif: "Songti SC", "STSong", "Times New Roman", serif;
    --font-mono: ui-monospace, SFMono-Regular, Consolas, monospace;

    /* 间距 */
    --space-sm: 2rem;
    --space-md: 4rem;
    --space-lg: 8vw;
    --space-xl: 10vw;
}

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

body {
    font-family: var(--font-body);
    background-color: var(--bg-base);
    color: var(--text-primary);
    line-height: 1.7;
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
}

a {
    text-decoration: none;
    color: inherit;
}

button {
    border: none;
    background: none;
    cursor: pointer;
    font-family: inherit;
}

/* ========= 中英双语控制 ========= */
.lang-zh,
.lang-en {
    display: none;
}

html[lang="zh-CN"] .lang-zh {
    display: inline;
}

html[lang="en"] .lang-en {
    display: inline;
}

/* 针对块级元素的特殊处理 */
html[lang="zh-CN"] div.lang-zh,
html[lang="zh-CN"] p.lang-zh {
    display: block;
}

html[lang="en"] div.lang-en,
html[lang="en"] p.lang-en {
    display: block;
}

/* ============================== */

/* 基础容器 */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 6vw;
    position: relative;
}

/* 文字排版 */
.head-massive {
    font-family: var(--font-display);
    font-size: clamp(2.5rem, 4.5vw, 4.5rem);
    font-weight: 600;
    line-height: 1.15;
    letter-spacing: -0.02em;
    color: var(--text-primary);
}

.head-section {
    font-family: var(--font-display);
    font-size: clamp(2rem, 3.5vw, 3.5rem);
    font-weight: 500;
    line-height: 1.2;
    letter-spacing: -0.02em;
}

.head-serif {
    font-family: var(--font-serif);
    font-size: clamp(1.8rem, 3.5vw, 3.5rem);
    font-weight: 400;
    line-height: 1.4;
    color: var(--text-primary);
}

.text-body {
    font-size: clamp(1rem, 1.1vw, 1.15rem);
    line-height: 1.9;
    color: var(--text-secondary);
    font-weight: 400;
    max-width: 650px;
}

.text-small {
    font-size: 0.95rem;
    line-height: 1.7;
    color: var(--text-secondary);
}

.tag-micro {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.15em;
    color: var(--brand-accent);
    font-weight: 600;
    margin-bottom: 1.25rem;
    display: inline-block;
}

/* 统一按钮 */
.btn-primary {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    background-color: var(--brand-main);
    color: #ffffff !important;
    padding: 16px 36px;
    font-size: 0.95rem;
    font-weight: 500;
    letter-spacing: 0.05em;
    border: 1px solid var(--brand-main);
    transition: all 0.3s ease;
}

.btn-primary:hover {
    background-color: transparent;
    color: var(--text-primary) !important;
}

/* 导航栏专属强引导下载按钮 */
.btn-header-dl {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    background-color: var(--brand-main);
    color: #ffffff !important;
    padding: 8px 20px;
    font-size: 0.85rem;
    font-weight: 500;
    border: 1px solid var(--brand-main);
    transition: all 0.3s ease;
}

.btn-header-dl:hover {
    background-color: transparent;
    color: var(--brand-main) !important;
}

/* Header */
header {
    padding: 2.5rem 0;
    position: absolute;
    width: 100%;
    z-index: 50;
}

.hero,
.doc-header {
    padding-top: max(22vh, 160px);
    padding-bottom: 5vh;
}

.nav-inner {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-links {
    display: flex;
    gap: 3vw;
    align-items: center;
    /* Removed absolute positioning to prevent overlap on smaller screens */
    flex: 1;
    justify-content: center;
}

.nav-item {
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--text-secondary);
    transition: color 0.3s;
}

.nav-item:hover {
    color: var(--text-primary);
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: 1.5rem;
}

.logo {
    font-family: var(--font-display);
    font-size: 1.25rem;
    font-weight: 600;
    letter-spacing: -0.02em;
    color: var(--text-primary);
}

.lang-switch {
    font-size: 0.85rem;
    font-weight: 500;
    padding: 6px 16px;
    color: var(--text-secondary);
    border: 1px solid var(--border-light);
    transition: all 0.3s;
}

.lang-switch:hover {
    border-color: var(--brand-main);
    color: var(--text-primary);
}

/* Common Layout Basics */
.section-padding {
    padding: var(--space-xl) 0;
}

.bg-alt {
    background-color: var(--bg-alt);
    border-top: 1px solid var(--border-light);
    border-bottom: 1px solid var(--border-light);
}

.divider {
    width: 100%;
    height: 1px;
    background-color: var(--border-light);
    margin: var(--space-lg) 0;
}

.divider-vertical {
    width: 1px;
    height: 40px;
    background-color: var(--border-light);
    margin: 1rem 0;
}

/* Footer */
footer {
    padding: var(--space-xl) 0 var(--space-md);
    text-align: center;
}

.footer-cta {
    margin-bottom: var(--space-lg);
}

.footer-cta .head-serif {
    margin-bottom: 2rem;
    line-height: 1.3;
}

.footer-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.85rem;
    color: var(--text-tertiary);
    border-top: 1px solid var(--border-light);
    padding-top: 2rem;
    flex-wrap: wrap;
    gap: 1rem;
    margin-top: 3rem;
}

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

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

/* Scroll Animation Common */
.reveal {
    opacity: 0;
    transform: translateY(20px);
    transition: all 0.8s cubic-bezier(0.16, 1, 0.3, 1);
}

.reveal.active {
    opacity: 1;
    transform: translateY(0);
}

/* Mobile Nav/Global Override */
@media (max-width: 768px) {
    .nav-links {
        display: none;
    }

    .nav-actions {
        gap: 0.8rem;
    }

    .lang-switch {
        padding: 4px 10px;
        font-size: 0.8rem;
    }

    .btn-header-dl {
        padding: 6px 14px;
        font-size: 0.8rem;
    }
}