:root {
    --bg-main: #0d1117;
    --bg-side: #010409;
    --border-color: #30363d;
    --text-primary: #c9d1d9;
    --text-secondary: #8b949e;
    --accent: #58a6ff;
    --accent-bg: rgba(56, 139, 253, 0.15);
    --code-bg: #161b22;
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
    --font-mono: 'Fira Code', ui-monospace, SFMono-Regular, SF Mono, Menlo, Consolas, Liberation Mono, monospace;
}

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

body {
    background-color: var(--bg-main);
    color: var(--text-primary);
    font-family: var(--font-sans);
    line-height: 1.6;
    overflow-x: hidden;
}

/* Navigation */
.top-nav {
    position: sticky;
    top: 0;
    background: var(--bg-side);
    border-bottom: 1px solid var(--border-color);
    padding: 12px 0;
    z-index: 1000;
}

.nav-container {
    max-width: 1400px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 40px;
}

.logo {
    font-weight: 700;
    font-size: 1.25rem;
    display: flex;
    align-items: center;
    gap: 10px;
}

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

.search-box {
    position: relative;
    width: 300px;
}

.search-box i {
    position: absolute;
    left: 12px;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-secondary);
}

.search-box input {
    width: 100%;
    background: var(--code-bg);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    padding: 8px 12px 8px 36px;
    color: var(--text-primary);
    outline: none;
    transition: 0.2s;
}

.search-box input:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-bg);
}

/* Layout */
.app-layout {
    display: flex;
    max-width: 1400px;
    margin: 40px auto;
    padding: 0 40px;
}

.sidebar {
    width: 280px;
    position: sticky;
    top: 100px;
    height: calc(100vh - 120px);
    overflow-y: auto;
    padding-right: 20px;
}

.sidebar-header {
    font-size: 0.8rem;
    text-transform: uppercase;
    color: var(--text-secondary);
    letter-spacing: 0.05em;
    font-weight: 700;
    margin-bottom: 16px;
}

.toc-nav {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.toc-link {
    text-decoration: none;
    color: var(--text-secondary);
    font-size: 0.95rem;
    padding: 6px 12px;
    border-radius: 6px;
    transition: 0.2s;
}

.toc-link:hover,
.toc-link.active {
    color: var(--text-primary);
    background: var(--code-bg);
}

.toc-link.active {
    border-left: 2px solid var(--accent);
    border-radius: 0 6px 6px 0;
}

.content-area {
    flex: 1;
    max-width: 900px;
    margin-left: 40px;
}

/* Header & Typography */
.readme-header {
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 32px;
    margin-bottom: 40px;
}

.readme-header h1 {
    font-size: 2.5rem;
    margin-bottom: 16px;
}

.version {
    font-size: 1rem;
    color: var(--text-secondary);
    font-weight: 400;
    background: var(--code-bg);
    padding: 4px 10px;
    border-radius: 40px;
    margin-left: 12px;
}

.lead {
    font-size: 1.25rem;
    color: var(--text-secondary);
}

.badges {
    display: flex;
    gap: 12px;
    margin-bottom: 24px;
}

.badge {
    padding: 4px 12px;
    border-radius: 40px;
    font-size: 0.75rem;
    font-weight: 600;
}

.badge-blue {
    background: #053b6d;
    color: #58a6ff;
}

.badge-green {
    background: #1b4721;
    color: #7ee787;
}

.badge-purple {
    background: #4c2889;
    color: #d2a8ff;
}

/* Sections */
.doc-section {
    margin-bottom: 60px;
    scroll-margin-top: 100px;
}

.doc-section h2 {
    font-size: 1.75rem;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 12px;
    margin-bottom: 24px;
}

.doc-section p {
    margin-bottom: 20px;
}

.module-card {
    background: var(--code-bg);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 24px;
    margin-bottom: 24px;
    transition: 0.2s;
}

.module-card:hover {
    border-color: var(--accent);
}

.module-meta {
    display: flex;
    justify-content: space-between;
    margin-top: 20px;
    color: var(--text-secondary);
    font-size: 0.85rem;
}

/* Skeleton */
.skeleton-line {
    height: 16px;
    background: var(--code-bg);
    border-radius: 4px;
    margin-bottom: 12px;
    animation: pulse 1.5s infinite;
}

.skeleton-section {
    height: 200px;
    background: var(--code-bg);
    border-radius: 12px;
    margin-bottom: 40px;
    animation: pulse 1.5s infinite;
}

@keyframes pulse {
    0% {
        opacity: 0.5;
    }

    50% {
        opacity: 0.8;
    }

    100% {
        opacity: 0.5;
    }
}

/* Modal & Playground */
.modal {
    display: none;
    position: fixed;
    z-index: 2000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.85);
    backdrop-filter: blur(8px);
    align-items: center;
    justify-content: center;
}

.modal.active {
    display: flex;
}

.modal-content {
    background: var(--bg-side);
    width: 90%;
    max-width: 1200px;
    height: 85vh;
    border-radius: 16px;
    border: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    overflow: hidden;
    box-shadow: 0 30px 60px rgba(0, 0, 0, 0.5);
}

.modal-header {
    background: var(--bg-main);
    padding: 16px 24px;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.file-info {
    display: flex;
    align-items: center;
    gap: 12px;
    font-weight: 600;
}

.file-info i {
    color: var(--accent);
}

.header-actions {
    display: flex;
    gap: 16px;
    align-items: center;
}

.btn-run {
    background: var(--accent);
    color: white;
    border: none;
    padding: 8px 20px;
    border-radius: 6px;
    font-weight: 600;
    cursor: pointer;
    transition: 0.2s;
    display: flex;
    align-items: center;
    gap: 8px;
}

.btn-run:hover {
    opacity: 0.9;
    transform: translateY(-1px);
}

.btn-run:disabled {
    background: var(--text-secondary);
    cursor: not-allowed;
}

.btn-ghost {
    background: transparent;
    border: 1px solid var(--border-color);
    color: var(--text-secondary);
    padding: 8px 16px;
    border-radius: 6px;
    font-weight: 600;
    cursor: pointer;
    transition: 0.2s;
    display: flex;
    align-items: center;
    gap: 8px;
}

.btn-ghost:hover {
    color: var(--text-primary);
    background: var(--code-bg);
    border-color: var(--text-secondary);
}

.btn-ghost.active {
    color: var(--accent);
    border-color: var(--accent);
    background: var(--accent-bg);
}

.close-modal {
    background: transparent;
    border: none;
    color: var(--text-secondary);
    font-size: 1.25rem;
    cursor: pointer;
}

/* Monaco Editor Container */
#monaco-editor-container {
    height: 100%;
    width: 100%;
}

.playground-body {
    flex: 1;
    display: grid;
    grid-template-columns: 1fr 400px;
    overflow: hidden;
}

.editor-pane {
    position: relative;
    background: #1e1e1e;
    overflow: hidden;
    /* Monaco handles scroll */
}

/* Individual Lesson Hover */
.lesson-item {
    background: transparent;
    transition: all 0.2s ease;
}

.lesson-item:hover {
    background: var(--accent-bg) !important;
    padding-left: 16px !important;
    /* Slight organic slide effect */
}

.editor-pane.edit-active {
    outline: 2px solid var(--accent);
    outline-offset: -2px;
}

.output-pane {
    background: #010409;
    border-left: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
}

.output-header {
    background: var(--bg-main);
    padding: 8px 16px;
    font-size: 0.75rem;
    text-transform: uppercase;
    font-weight: 700;
    color: var(--text-secondary);
    border-bottom: 1px solid var(--border-color);
}

#output-area {
    flex: 1;
    padding: 16px;
    margin: 0;
    font-family: var(--font-mono);
    font-size: 0.9rem;
    color: #a5d6ff;
    overflow-y: auto;
    white-space: pre-wrap;
    word-break: break-all;
}

/* Scrollbar Style */
::-webkit-scrollbar {
    width: 10px;
    height: 10px;
}

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

::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 5px;
}

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

/* Footer */
.docs-footer {
    border-top: 1px solid var(--border-color);
    padding: 40px 0;
    margin-top: 80px;
    text-align: center;
}

@media (max-width: 992px) {
    .sidebar {
        display: none;
    }

    .content-area {
        margin-left: 0;
    }

    .playground-body {
        grid-template-columns: 1fr;
        grid-template-rows: 1fr 250px;
    }

    .output-pane {
        border-left: none;
        border-top: 1px solid var(--border-color);
    }
}