:root {
    --bg-color: #0d1117;
    --sidebar-bg: #161b22;
    --text-color: #c9d1d9;
    --text-dim: #8b949e;
    --accent-color: #58a6ff;
    --border-color: #30363d;
    --card-bg: #21262d;
    --hover-bg: #1f242b;
    --active-bg: #238636;
    --pain-color: #f85149;
    --cure-color: #3fb950;
    --code-bg: #010409;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    scrollbar-color: var(--border-color) var(--card-bg);
    scrollbar-width: thin;
}

*::-webkit-scrollbar {
    width: 8px;
    height: 6px;
}

*::-webkit-scrollbar-track {
    background: var(--card-bg);
}

*::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 4px;
}

*::-webkit-scrollbar-thumb:hover {
    background: var(--text-dim);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
}

.app-container {
    display: grid;
    grid-template-columns: 300px 1fr;
    height: 100vh;
}

/* Sidebar */
.sidebar {
    background-color: var(--sidebar-bg);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    overflow-y: auto;
}

.sidebar-header {
    padding: 24px;
    border-bottom: 1px solid var(--border-color);
}

.sidebar-header h1 {
    font-size: 1.2rem;
    color: var(--accent-color);
}

.sidebar-header p {
    font-size: 0.8rem;
    color: var(--text-dim);
}

.sidebar-nav {
    flex: 1;
}

#topic-list {
    list-style: none;
}

.topic-item {
    padding: 12px 24px;
    cursor: pointer;
    font-size: 0.9rem;
    border-bottom: 1px solid rgba(48, 54, 61, 0.5);
    transition: background 0.2s;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.topic-item:hover {
    background-color: var(--hover-bg);
}

.topic-item.active {
    background-color: var(--hover-bg);
    border-left: 4px solid var(--accent-color);
    color: white;
}

.topic-item.completed::after {
    content: "✅";
    font-size: 0.8rem;
    margin-left: 10px;
    opacity: 0.8;
}

/* Content Area */
.content-area {
    display: flex;
    flex-direction: column;
    overflow-y: auto;
    padding: 40px;
    max-width: 1000px;
    margin: 0 auto;
    width: 100%;
}

.welcome-screen {
    text-align: center;
    margin-top: 100px;
}

.welcome-screen h2 {
    font-size: 2rem;
    margin-bottom: 20px;
}

.content h1 {
    font-size: 2.5rem;
    margin-bottom: 30px;
    border-bottom: 2px solid var(--border-color);
    padding-bottom: 10px;
}

/* Context Cards */
.context-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
    margin-bottom: 24px;
}

.card {
    background-color: var(--card-bg);
    padding: 16px 20px;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    transition: transform 0.2s, border-color 0.2s;
}

.card:hover {
    transform: translateY(-4px);
    border-color: var(--text-dim);
}

.card h3 {
    margin-bottom: 16px;
    font-size: 1.2rem;
    display: flex;
    align-items: center;
    gap: 12px;
    font-weight: 600;
}

.card-pain { border-top: 4px solid var(--pain-color); }
.card-cure { border-top: 4px solid var(--cure-color); }

.card-pain h3 { color: var(--pain-color); }
.card-cure h3 { color: var(--cure-color); }

.card p {
    color: var(--text-color);
    font-size: 0.95rem;
    line-height: 1.5;
}

/* Explanation */
.explanation {
    margin-bottom: 40px;
    font-size: 1.1rem;
    color: var(--text-color);
    padding: 0 10px;
}

.explanation h2 {
    margin-top: 2.5rem;
    margin-bottom: 1rem;
}

.explanation hr {
    margin-top: 2.5rem;
    margin-bottom: 2.5rem;
    border: none;
    border-top: 1px solid var(--border-color);
}

.explanation blockquote {
    margin: 1.5rem 0;
    padding: 0.75rem 1.25rem;
    border-left: 3px solid var(--accent-color);
    color: var(--text-dim);
    font-style: italic;
}

.explanation p {
    margin-bottom: 1.1rem;
}

.explanation ul,
.explanation ol {
    list-style: none;
    padding-left: 1.5rem;
    margin: 1rem 0;
}

.explanation li {
    margin-bottom: 0.6rem;
    line-height: 1.7;
    padding-left: 0.5rem;
    border-left: 2px solid var(--border-color);
}

.explanation a {
    display: inline-block;
    color: var(--accent-color);
    border: 1px solid var(--accent-color);
    padding: 2px 10px;
    border-radius: 4px;
    font-size: 0.85rem;
    text-decoration: none;
    margin-left: 0.4rem;
    vertical-align: middle;
    transition: background-color 0.2s, color 0.2s;
}

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

.explanation pre {
    margin: 1.5rem 0;
}

.explanation p + pre,
.explanation pre + p {
    margin-top: 1.5rem;
}

/* Code Blocks */
.code-container {
    background-color: var(--code-bg);
    padding: 20px;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    position: relative;
    margin-bottom: 40px;
}

.code-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 15px;
    font-size: 0.8rem;
    color: var(--text-dim);
}

pre {
    font-family: "JetBrains Mono", "Fira Code", monospace;
    font-size: 0.9rem;
    overflow-x: auto;
}

.github-link {
    color: var(--accent-color);
    text-decoration: none;
    border: 1px solid var(--accent-color);
    padding: 4px 12px;
    border-radius: 4px;
    transition: all 0.2s;
}

.github-link:hover {
    background-color: var(--accent-color);
    color: white;
}

/* Footer Navigation */
.content-footer {
    margin-top: auto;
    padding-top: 40px;
    display: flex;
    justify-content: space-between;
    border-top: 1px solid var(--border-color);
}

.nav-btn {
    background-color: var(--card-bg);
    color: var(--text-color);
    border: 1px solid var(--border-color);
    padding: 10px 20px;
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.2s;
}

.nav-btn:hover:not(:disabled) {
    border-color: var(--accent-color);
    color: var(--accent-color);
}

.nav-btn:disabled {
    opacity: 0.3;
    cursor: not-allowed;
}

/* Zoomable Image Viewer */
.image-viewer-container {
    margin-bottom: 0;
    position: relative;
    overflow: hidden;
    background-color: #000;
    border-radius: 12px 12px 0 0;
    border: 1px solid var(--border-color);
    border-bottom: none;
    touch-action: none;
}



.zoomable-image {
    width: 100%;
    height: auto;
    display: block;
    transition: transform 0.1s ease-out;
}

.zoom-controls {
    display: flex;
    flex-direction: row;
    gap: 8px;
    padding: 10px 14px;
    background-color: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 0 0 12px 12px;
    margin-bottom: 8px;
}

.zoom-btn {
    width: 36px;
    height: 36px;
    border-radius: 6px;
    background: var(--bg-color);
    border: 1px solid var(--border-color);
    color: var(--text-color);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.1rem;
    transition: all 0.2s;
}

.zoom-btn:hover {
    background: var(--accent-color);
    border-color: var(--accent-color);
    color: var(--bg-color);
}

.image-gallery {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.image-caption {
    text-align: center;
    font-size: 0.85rem;
    color: var(--text-dim);
    margin-top: 8px;
}

/* Sidebar toggle button — hidden on desktop */
.sidebar-toggle {
    display: none;
}

/* Sidebar backdrop — hidden by default */
.sidebar-backdrop {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.5);
    z-index: 99;
}

/* Mobile layout */
@media (max-width: 768px) {
    .app-container {
        grid-template-columns: 1fr;
    }

    .sidebar {
        position: fixed;
        top: 0;
        left: 0;
        height: 100vh;
        width: 300px;
        transform: translateX(-300px);
        transition: transform 0.3s ease;
        z-index: 100;
    }

    .content-area {
        width: 100%;
        padding: 56px 20px 20px;
    }

    .sidebar-toggle {
        display: flex;
        align-items: center;
        justify-content: center;
        position: fixed;
        top: 12px;
        left: 12px;
        z-index: 98;
        width: 40px;
        height: 40px;
        background: var(--card-bg);
        border: 1px solid var(--border-color);
        border-radius: 8px;
        color: var(--text-color);
        font-size: 1.2rem;
        cursor: pointer;
        transition: background 0.2s;
    }

    .sidebar-toggle:hover {
        background: var(--hover-bg);
    }

    .sidebar-backdrop {
        display: block;
        opacity: 0;
        pointer-events: none;
        transition: opacity 0.3s ease;
    }

    /* State: sidebar open */
    body.sidebar-open .sidebar {
        transform: translateX(0);
    }

    body.sidebar-open .sidebar-backdrop {
        opacity: 1;
        pointer-events: auto;
    }
}