:root {
    --bg-color: #FDFBF7;
    --text-color: #1a1a1a;
    --accent-color: #FF6600;
    --border-color: #EAEAEA;
    --sidebar-bg: #f7f5f2;
    --sidebar-width: 350px;
    --font-sans: 'IBM Plex Sans', sans-serif;
    --font-serif: 'IBM Plex Serif', serif;
    --font-hyperlegible: 'Atkinson Hyperlegible', sans-serif;
    --font-mono: 'JetBrains Mono', monospace;
    --muted-color: #777;
    --code-bg: #eee;
    --hover-bg: #e9e5e0;
    --accent-hover: #e85a00;
}

[data-theme="dark"] {
    --bg-color: #1a1a1a;
    --text-color: #e8e6e3;
    --accent-color: #FF7722;
    --border-color: #3a3a3a;
    --sidebar-bg: #242424;
    --muted-color: #aaa;
    --code-bg: #333;
    --hover-bg: #2a2a2a;
    --accent-hover: #ff9a44;
}

* { box-sizing: border-box; }

body {
    margin: 0;
    padding-left: var(--sidebar-width);
    background-color: var(--bg-color);
    color: var(--text-color);
    font-size: 17px;
    line-height: 1.7;
    transition: font-family 0.2s ease-in-out;
}

.font-plex-sans { font-family: var(--font-sans); }
.font-plex-serif { font-family: var(--font-serif); }
.font-hyperlegible { font-family: var(--font-hyperlegible); }
.font-jetbrains-mono { font-family: var(--font-mono); }

/* Sidebar */
.sidebar {
    position: fixed;
    top: 0;
    left: 0;
    width: var(--sidebar-width);
    height: 100vh;
    background-color: var(--sidebar-bg);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    z-index: 1000;
}

.sidebar-header {
    padding: 20px;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.sidebar-header h1 { font-size: 1.2em; margin: 0; }

.breadcrumb {
    font-size: 0.85em;
    color: var(--muted-color);
    margin-top: 0.5rem;
}

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

.breadcrumb a:hover {
    color: var(--accent-color);
}

/* TOC */
.toc-container {
    flex-grow: 1;
    overflow-y: auto;
    padding: 20px;
}

.toc {
    list-style: none;
    padding: 0;
    margin: 0;
}

.toc ul {
    list-style: none;
    padding-left: 15px;
    margin-top: 5px;
}

.toc a {
    display: block;
    padding: 4px 8px;
    border-radius: 4px;
    color: var(--muted-color);
    text-decoration: none;
    font-size: 0.9em;
    transition: all 0.2s ease;
}

.toc a:hover {
    background-color: var(--hover-bg);
}

.toc a.active {
    background-color: #ffead9;
    color: var(--accent-color);
    font-weight: 600;
    border-left: 3px solid var(--accent-color);
}

[data-theme="dark"] .toc a.active {
    background-color: #2a1f15;
}

/* Sidebar Footer */
.sidebar-footer {
    padding: 20px;
    border-top: 1px solid var(--border-color);
}

.font-picker, .style-picker, .theme-picker {
    display: flex;
    gap: 6px;
    margin-bottom: 16px;
    flex-wrap: wrap;
    justify-content: center;
}

/* Unified button styling */
.font-picker button,
.style-btn,
.copy-markdown-btn,
.print-btn,
.theme-toggle-btn,
.nav-btn {
    padding: 6px 12px;
    border: 1px solid var(--border-color);
    background: transparent;
    color: var(--text-color);
    cursor: pointer;
    border-radius: 4px;
    font-size: 0.8em;
    font-weight: 500;
    transition: all 0.2s ease;
    white-space: nowrap;
    text-decoration: none;
    text-align: center;
}

.font-picker button:hover,
.style-btn:hover,
.copy-markdown-btn:hover,
.print-btn:hover,
.theme-toggle-btn:hover,
.nav-btn:hover {
    background: var(--hover-bg);
    color: var(--text-color);
    text-decoration: none;
}

/* Active states */
.font-picker button.active,
.style-btn.active,
.theme-toggle-btn.active {
    color: var(--accent-color);
    border-color: var(--accent-color);
    background: transparent;
    font-weight: 700;
}

/* Full-width buttons */
.copy-markdown-btn,
.print-btn,
.theme-toggle-btn,
.nav-btn {
    width: 100%;
    margin-bottom: 10px;
}

/* Copy success state */
.copy-markdown-btn.success {
    color: var(--accent-color);
    border-color: var(--accent-color);
    background: transparent;
    font-weight: 700;
}

/* Navigation buttons */
.nav-buttons {
    display: flex;
    flex-direction: column;
    gap: 8px;
    margin-bottom: 15px;
}

.nav-btn.primary {
    background: var(--accent-color);
    color: #fff;
    border-color: var(--accent-color);
}

.nav-btn.primary:hover {
    background: var(--accent-hover);
    border-color: var(--accent-hover);
}

.disclaimer {
    font-size: 0.75em;
    color: var(--muted-color);
    line-height: 1.4;
    margin: 0;
}

/* Main content */
.content {
    max-width: 1000px;
    margin: 0 auto;
    padding: 40px;
    box-sizing: border-box;
}

/* Index page styles */
.unit-link, .lecture-link {
    color: var(--text-color);
    text-decoration: none;
    font-weight: 500;
}

.unit-link:hover, .lecture-link:hover {
    color: var(--accent-color);
}

.unit-count {
    color: var(--muted-color);
    font-size: 0.9em;
    margin-top: 0.25rem;
}

.subtitle {
    color: var(--muted-color);
    margin-bottom: 3rem;
    font-size: 1.1em;
}

.back-link {
    color: var(--text-color);
    text-decoration: none;
    margin-bottom: 2rem;
    display: inline-block;
    font-size: 1em;
}

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

/* Content sections */
.content-section {
    padding-bottom: 20px;
}

.content-section:not(:last-child) {
    border-bottom: 1px solid var(--border-color);
    margin-bottom: 40px;
}

/* Typography */
h1, h2, h3, h4 {
    position: relative;
    scroll-margin-top: 20px;
}

h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.3;
    margin: 2.5rem 0 1rem 0;
}

h1 { font-size: 2.5em; }
h2 { font-size: 2em; }
h3 { font-size: 1.5em; }

p { margin: 1rem 0; }

blockquote {
    border-left: 3px solid var(--accent-color);
    padding-left: 20px;
    margin: 1.5rem 0;
    color: var(--muted-color);
}

code {
    background: var(--code-bg);
    padding: 2px 5px;
    border-radius: 4px;
    font-family: monospace;
    font-size: 0.9em;
}

pre > code {
    display: block;
    padding: 15px;
    overflow-x: auto;
}

img {
    max-width: 100%;
    padding: 20px;
    border: 2px solid var(--accent-color);
}

/* Mobile hamburger and backdrop - hidden by default */
.hamburger-menu {
    display: none;
}

.sidebar-backdrop {
    display: none;
}

/* Mobile responsive */
@media (max-width: 767px) {
    body {
        padding-left: 0;
    }
    
    body.sidebar-open {
        overflow: hidden;
        position: fixed;
        width: 100%;
    }
    
    .sidebar {
        transform: translateX(-100%);
        transition: transform 0.3s ease;
    }
    
    body.sidebar-open .sidebar {
        transform: translateX(0);
    }
    
    .hamburger-menu {
        display: block;
        position: fixed;
        top: 20px;
        left: 20px;
        z-index: 1001;
        background: var(--sidebar-bg);
        border: 1px solid var(--border-color);
        padding: 10px;
        border-radius: 4px;
        font-size: 1.5em;
        cursor: pointer;
        color: var(--text-color);
    }
    
    body.sidebar-open .hamburger-menu {
        background: var(--accent-color);
        color: white;
    }
    
    .sidebar-backdrop {
        position: fixed;
        inset: 0;
        background: rgba(0,0,0,0.5);
        z-index: 999;
    }
    
    body.sidebar-open .sidebar-backdrop {
        display: block;
    }
    
    .content {
        padding: 20px;
        max-width: 100%;
        width: 100%;
    }
}

/* Print styles */
@media print {
    .sidebar,
    .sidebar-backdrop,
    .hamburger-menu {
        display: none;
    }
    
    body {
        padding-left: 0;
        background: white;
        color: black;
        font-size: 11px;
    }
    
    .content {
        max-width: none;
        padding: 20px;
        margin: 0;
    }
    
    h1 { font-size: 1.4em; }
    h2 { font-size: 1.2em; }
    h3 { font-size: 1em; }
    h4 { font-size: 0.9em; }
    h5 { font-size: 0.85em; }
    h6 { font-size: 0.8em; }
    
    img {
        max-width: 40%;
        page-break-inside: avoid;
        border: none;
        padding: 5px 0;
        display: block;
        margin: 10px auto;
    }
    
    h1, h2, h3, h4 {
        page-break-after: avoid;
    }
}