/* ===================================
   CSS Variables & Design Tokens
   =================================== */
:root {
    --color-primary: #3730a3;
    --color-primary-hover: #4338ca;
    --color-primary-light: #e0e7ff;
    --color-bg-primary: #fdfdfd;
    --color-bg-secondary: #f8f9fa;
    --color-bg-tertiary: #f0f0f5;
    --color-bg-card: #ffffff;
    --color-bg-code: #1e1e2e;
    --color-text-primary: #1a1a2e;
    --color-text-secondary: #4b5563;
    --color-text-muted: #6b7280;
    --color-text-inverse: #ffffff;
    --color-border: #e5e7eb;
    --color-border-light: #f3f4f6;
    --font-sans: 'Outfit', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-serif: 'Outfit', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-mono: 'SF Mono', 'Consolas', monospace;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 1.875rem;
    --font-size-4xl: 2.25rem;
    --font-size-5xl: 3rem;
    --font-weight-normal: 400;
    --font-weight-medium: 500;
    --font-weight-semibold: 600;
    --font-weight-bold: 700;
    --font-weight-extrabold: 800;
    --line-height-tight: 1.25;
    --line-height-normal: 1.5;
    --line-height-relaxed: 1.75;
    --spacing-1: 0.25rem;
    --spacing-2: 0.5rem;
    --spacing-3: 0.75rem;
    --spacing-4: 1rem;
    --spacing-5: 1.25rem;
    --spacing-6: 1.5rem;
    --spacing-8: 2rem;
    --spacing-10: 2.5rem;
    --spacing-12: 3rem;
    --spacing-16: 4rem;
    --max-width: 1440px;
    --sidebar-width: 260px;
    --toc-width: 240px;
    --header-height: 64px;
    --radius-sm: 0.25rem;
    --radius-md: 0.375rem;
    --radius-lg: 0.5rem;
    --radius-xl: 0.75rem;
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --transition-fast: 150ms ease;
    --transition-normal: 200ms ease;
    --z-sticky: 200;
    --z-header: 300;
    --z-overlay: 400;
}

[data-theme="dark"] {
    /* Material Design 3 Dark Theme Colors */
    /* Surface colors using Material tonal palette */
    --color-bg-primary: #121212;
    /* Surface */
    --color-bg-secondary: #1e1e1e;
    /* Surface +1 elevation */
    --color-bg-tertiary: #2c2c2c;
    /* Surface +2 elevation */
    --color-bg-card: #1e1e1e;
    /* Surface Container */
    --color-bg-code: #0d0d0d;
    /* Surface Dim */

    /* Text colors following Material contrast guidelines */
    --color-text-primary: #e6e1e5;
    /* On Surface */
    --color-text-secondary: #cac4d0;
    /* On Surface Variant */
    --color-text-muted: #938f99;
    /* Outline */

    /* Border colors */
    --color-border: #49454f;
    /* Outline Variant */
    --color-border-light: #79747e;
    /* Outline */

    /* Primary color adjustments for dark mode */
    --color-primary: #d0bcff;
    /* Primary (light purple for dark bg) */
    --color-primary-hover: #e8ddff;
    /* Primary lighter on hover */
    --color-primary-light: #4f378b;
    /* Primary Container */

    /* Shadows for dark mode (more subtle) */
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 8px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 8px 16px rgba(0, 0, 0, 0.5);
}

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

html {
    scroll-behavior: smooth;
    scroll-padding-top: calc(var(--header-height) + var(--spacing-8));
}

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

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

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

ul,
ol {
    list-style: none;
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

::-webkit-scrollbar {
    width: 6px;
    height: 6px;
}

::-webkit-scrollbar-track {
    background: transparent;
}

::-webkit-scrollbar-thumb {
    background: var(--color-border);
    border-radius: 3px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--color-text-muted);
}

/* Header */
.header {
    position: sticky;
    top: 0;
    z-index: var(--z-header);
    width: 100%;
    height: var(--header-height);
    background-color: rgba(253, 253, 253, 0.95);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--color-border);
    transition: background-color var(--transition-normal);
}

[data-theme="dark"] .header {
    background-color: rgba(18, 18, 18, 0.95);
}

.header-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    max-width: var(--max-width);
    height: 100%;
    margin: 0 auto;
    padding: 0 var(--spacing-6);
}

.header-left {
    display: flex;
    align-items: center;
    gap: var(--spacing-8);
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-3);
    transition: opacity var(--transition-fast);
}

.logo:hover {
    opacity: 0.8;
}

.logo-icon {
    width: 32px;
    height: 32px;
    color: var(--color-text-primary);
}

.logo-text {
    font-family: var(--font-sans);
    font-size: var(--font-size-xl);
    font-weight: var(--font-weight-bold);
    letter-spacing: -0.025em;
}

.search-box {
    position: relative;
    width: 280px;
    display: none;
}

@media (min-width: 768px) {
    .search-box {
        display: block;
    }
}

@media (min-width: 1024px) {
    .search-box {
        width: 320px;
    }
}

.search-box input {
    width: 100%;
    padding: var(--spacing-2) var(--spacing-10);
    font-family: var(--font-sans);
    font-size: var(--font-size-sm);
    color: var(--color-text-primary);
    background-color: var(--color-bg-tertiary);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
}

.search-box input:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px var(--color-primary-light);
}

.search-box input::placeholder {
    color: var(--color-text-muted);
}

.search-icon {
    position: absolute;
    left: var(--spacing-3);
    top: 50%;
    transform: translateY(-50%);
    font-size: 20px;
    color: var(--color-text-muted);
    pointer-events: none;
}

.search-shortcut {
    position: absolute;
    right: var(--spacing-3);
    top: 50%;
    transform: translateY(-50%);
    display: none;
    padding: 2px 6px;
    font-family: var(--font-sans);
    font-size: 10px;
    font-weight: var(--font-weight-medium);
    color: var(--color-text-muted);
    background-color: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
}

@media (min-width: 1024px) {
    .search-shortcut {
        display: inline-flex;
    }
}

.header-right {
    display: none;
    align-items: center;
    gap: var(--spacing-4);
}

@media (min-width: 1024px) {
    .header-right {
        display: flex;
    }
}

.header-nav {
    display: flex;
    align-items: center;
    gap: var(--spacing-6);
}

.nav-link {
    font-family: var(--font-sans);
    font-size: var(--font-size-sm);
    font-weight: var(--font-weight-medium);
    color: var(--color-text-primary);
    transition: color var(--transition-fast);
}

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

.header-divider {
    width: 1px;
    height: 24px;
    background-color: var(--color-border);
}

.theme-toggle {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    color: var(--color-text-secondary);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
}

.theme-toggle:hover {
    background-color: var(--color-bg-tertiary);
    color: var(--color-text-primary);
}

.theme-toggle .dark-icon {
    display: none;
}

[data-theme="dark"] .theme-toggle .light-icon {
    display: none;
}

[data-theme="dark"] .theme-toggle .dark-icon {
    display: block;
}

.cta-button {
    padding: var(--spacing-2) var(--spacing-5);
    font-family: var(--font-sans);
    font-size: var(--font-size-sm);
    font-weight: var(--font-weight-semibold);
    color: var(--color-text-inverse);
    background-color: var(--color-primary);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    transition: background-color var(--transition-fast);
}

.cta-button:hover {
    background-color: var(--color-primary-hover);
}

.mobile-menu-toggle {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    color: var(--color-text-primary);
}

@media (min-width: 1024px) {
    .mobile-menu-toggle {
        display: none;
    }
}