:root {
    --font-sans: 'Outfit', 'Noto Sans TC', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    --font-mono: 'JetBrains Mono', monospace;

    /* Light Theme Palette */
    --bg-base: #f8fafc;
    --bg-surface: #ffffff;
    --border-color: #e2e8f0;
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-muted: #94a3b8;
    --accent-primary: #2563eb;
    --accent-glow: rgba(37, 99, 235, 0.1);
    --accent-hover: #1d4ed8;
    --code-bg: #f1f5f9;
    --code-text: #0f172a;
    --shadow: 0 4px 20px -2px rgba(15, 23, 42, 0.05), 0 2px 10px -1px rgba(15, 23, 42, 0.03);
    --transition-speed: 0.3s;
    color-scheme: light;
}

@media (prefers-color-scheme: dark) {
    :root {
        --bg-base: #090d16;
        --bg-surface: #0f172a;
        --border-color: #1e293b;
        --text-primary: #f8fafc;
        --text-secondary: #94a3b8;
        --text-muted: #64748b;
        --accent-primary: #38bdf8;
        --accent-glow: rgba(56, 189, 248, 0.15);
        --accent-hover: #7dd3fc;
        --code-bg: #1e293b;
        --code-text: #38bdf8;
        --shadow: 0 10px 30px -10px rgba(0, 0, 0, 0.5);
        color-scheme: dark;
    }
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    transition: background-color var(--transition-speed), border-color var(--transition-speed);
}

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    background-color: var(--bg-base);
    color: var(--text-primary);
    font-family: var(--font-sans);
    line-height: 1.75;
    -webkit-font-smoothing: antialiased;
    padding-bottom: 80px;
}

header {
    max-width: 900px;
    margin: 0 auto;
    padding: 30px 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--border-color);
}

.logo {
    font-weight: 800;
    font-size: 1.5rem;
    letter-spacing: -0.03em;
    color: var(--text-primary);
    text-decoration: none;
    display: flex;
    align-items: center;
    gap: 8px;
}

.logo span {
    color: var(--accent-primary);
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 20px;
}

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

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

/* Premium Theme Toggle Button */
.theme-toggle-btn {
    background: none;
    border: 1px solid var(--border-color);
    padding: 8px 12px;
    border-radius: 9999px;
    color: var(--text-primary);
    cursor: pointer;
    font-family: var(--font-sans);
    font-size: 0.85rem;
    font-weight: 500;
    display: flex;
    align-items: center;
    gap: 6px;
    transition: all var(--transition-speed);
}

.theme-toggle-btn:hover {
    background-color: var(--code-bg);
    border-color: var(--accent-primary);
}

main {
    max-width: 900px;
    margin: 40px auto;
    padding: 0 20px;
}

/* Article Formatting */
article {
    background-color: var(--bg-surface);
    border: 1px solid var(--border-color);
    border-radius: 20px;
    padding: 40px;
    box-shadow: var(--shadow);
}

@media (max-width: 768px) {
    article {
        padding: 24px;
    }
}

article h1 {
    font-size: 2.25rem;
    font-weight: 800;
    line-height: 1.25;
    letter-spacing: -0.03em;
    margin-bottom: 16px;
    color: var(--text-primary);
}

/* Tag Styles */
.article-tags {
    margin-top: -4px;
    margin-bottom: 28px;
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.tag-badge {
    background-color: var(--code-bg);
    color: var(--accent-primary);
    border: 1px solid var(--border-color);
    padding: 2px 10px;
    border-radius: 9999px;
    font-size: 0.8rem;
    font-family: var(--font-mono);
    text-decoration: none;
    transition: all var(--transition-speed);
    display: inline-block;
    white-space: nowrap;
}

.tag-badge:hover {
    background-color: var(--accent-primary);
    color: var(--bg-surface);
    border-color: var(--accent-primary);
}

article h2 {
    font-size: 1.6rem;
    font-weight: 700;
    margin-top: 40px;
    margin-bottom: 16px;
    border-left: 4px solid var(--accent-primary);
    padding-left: 12px;
    letter-spacing: -0.02em;
}

article h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-top: 28px;
    margin-bottom: 12px;
    color: var(--text-primary);
}

article p {
    margin-bottom: 20px;
    color: var(--text-secondary);
    font-size: 1.05rem;
    text-align: justify;
}

article ul,
article ol {
    margin-bottom: 20px;
    padding-left: 24px;
    color: var(--text-secondary);
}

article li {
    margin-bottom: 8px;
}

article blockquote {
    border-left: 4px solid var(--border-color);
    padding: 10px 20px;
    margin: 20px 0;
    background-color: var(--bg-base);
    border-radius: 0 8px 8px 0;
    font-style: italic;
}

article blockquote p {
    margin-bottom: 0;
}

/* Superscript Footnotes Links */
a[href^="#fn-"],
a[href^="#ref-"] {
    font-size: 0.75em;
    line-height: 0;
    position: relative;
    vertical-align: super;
    text-decoration: none;
    font-weight: 700;
    color: var(--accent-primary);
    padding: 0 2px;
}

a[href^="#fn-"]:hover,
a[href^="#ref-"]:hover {
    text-decoration: underline;
}

/* Mapping Table Styling */
.mapping-table,
table {
    width: 100%;
    border-collapse: collapse;
    margin: 30px 0;
    font-size: 0.95rem;
    overflow-x: auto;
    display: block;
}

@media (min-width: 600px) {

    .mapping-table,
    table {
        display: table;
    }
}

.mapping-table th,
.mapping-table td,
table th,
table td {
    border: 1px solid var(--border-color);
    padding: 14px;
    text-align: left;
}

.mapping-table th,
table th {
    background-color: var(--code-bg);
    color: var(--text-primary);
    font-weight: 700;
}

.mapping-table td,
table td {
    color: var(--text-secondary);
}

/* Code Blocks */
pre {
    background-color: var(--code-bg);
    padding: 20px;
    border-radius: 12px;
    overflow-x: auto;
    margin: 24px 0;
    border: 1px solid var(--border-color);
}

code {
    font-family: var(--font-mono);
    font-size: 0.9em;
    color: var(--code-text);
    padding: 2px 6px;
    background-color: var(--code-bg);
    border-radius: 4px;
}

pre code {
    padding: 0;
    background-color: transparent;
    border-radius: 0;
    color: var(--text-primary);
}

hr {
    border: none;
    border-top: 1px solid var(--border-color);
    margin: 40px 0;
}

/* Footer / Footnote Area */
.footer-nav {
    max-width: 900px;
    margin: 40px auto 0 auto;
    text-align: center;
    font-size: 0.85rem;
    color: var(--text-muted);
}

.language-switcher {
    margin-top: 20px;
    display: flex;
    justify-content: center;
    gap: 12px;
}

.lang-btn {
    background: none;
    border: 1px solid var(--border-color);
    padding: 4px 12px;
    border-radius: 4px;
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.8rem;
    transition: all var(--transition-speed);
}

.lang-btn:hover,
.lang-btn.active {
    border-color: var(--accent-primary);
    color: var(--accent-primary);
    background-color: var(--accent-glow);
}

/* Math equations alignment */
.katex-display,
p>iframe {
    overflow-x: auto;
    margin: 20px 0;
}