/* =====================================================
   Fyzika 1 — Public Design System
   ===================================================== */

/* 1. Design Tokens
   ===================================================== */
:root {
    /* Colors */
    --c-bg:          #F9FAFB;
    --c-surface:     #FFFFFF;
    --c-border:      #E5E7EB;
    --c-border-light:#F3F4F6;
    --c-text:        #111827;
    --c-text-2:      #6B7280;
    --c-text-3:      #9CA3AF;
    --c-accent:      #3B82F6;
    --c-accent-dark: #2563EB;
    --c-accent-bg:   #EFF6FF;

    /* Typography */
    --font-sans:  'Inter', system-ui, -apple-system, sans-serif;
    --font-serif: 'Playfair Display', Georgia, serif;
    --font-mono:  'JetBrains Mono', 'Fira Code', monospace;

    /* Spacing */
    --header-h: 60px;
    --radius:    8px;
    --radius-lg: 12px;

    /* Transitions */
    --ease: 0.18s ease;
}

/* 2. Base
   ===================================================== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html { scroll-behavior: smooth; }

body {
    font-family: var(--font-sans);
    font-size: 16px;
    line-height: 1.6;
    color: var(--c-text);
    background: var(--c-bg);
    -webkit-font-smoothing: antialiased;
    padding-top: var(--header-h);
}

a { color: inherit; text-decoration: none; }
img { max-width: 100%; height: auto; }
button { font-family: inherit; cursor: pointer; }

/* 3. Layout
   ===================================================== */
.site-main {
    min-height: calc(100vh - var(--header-h) - 60px);
}

.site-footer {
    background: var(--c-surface);
    border-top: 1px solid var(--c-border);
    padding: 20px 24px;
}

.footer-inner {
    max-width: 1200px;
    margin: 0 auto;
    text-align: center;
    font-size: 13px;
    color: var(--c-text-3);
}

.footer-inner p {
    margin: 4px 0;
}

.footer-source {
    font-size: 12px;
    color: var(--c-text-3);
}

/* 4. Lessons Index
   ===================================================== */
.lessons-page {
    padding: 48px 24px 80px;
}

.lessons-container {
    max-width: 800px;
    margin: 0 auto;
}

/* Page heading row */
.lessons-header {
    display: flex;
    align-items: flex-end;
    justify-content: space-between;
    gap: 16px;
    margin-bottom: 40px;
    padding-bottom: 24px;
    border-bottom: 1px solid var(--c-border);
}

.lessons-header__title {
    font-family: var(--font-serif);
    font-size: 36px;
    font-weight: 700;
    line-height: 1.2;
    color: var(--c-text);
    letter-spacing: -0.02em;
}

.lessons-header__subtitle {
    margin-top: 6px;
    font-size: 15px;
    color: var(--c-text-2);
}

.lessons-header__meta {
    display: flex;
    align-items: center;
    gap: 8px;
    flex-shrink: 0;
}

.search-tag {
    display: inline-flex;
    align-items: center;
    gap: 5px;
    padding: 4px 10px;
    background: var(--c-accent-bg);
    color: var(--c-accent);
    font-size: 13px;
    font-weight: 500;
    border-radius: 100px;
    max-width: 180px;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.lessons-count {
    font-size: 13px;
    font-weight: 500;
    color: var(--c-text-3);
    white-space: nowrap;
}

/* Lesson list */
.lessons-list {
    display: flex;
    flex-direction: column;
}

.lesson-item {
    display: flex;
    align-items: center;
    gap: 20px;
    padding: 18px 16px;
    border-bottom: 1px solid var(--c-border-light);
    border-radius: var(--radius);
    transition: background var(--ease), border-color var(--ease);
    color: var(--c-text);
    text-decoration: none;
}

.lesson-item:first-child {
    border-top: 1px solid var(--c-border-light);
}

.lesson-item:hover {
    background: var(--c-accent-bg);
    border-color: transparent;
}

.lesson-item:hover .lesson-item__num {
    color: var(--c-accent);
}

.lesson-item:hover .lesson-item__arrow {
    opacity: 1;
    transform: translateX(3px);
}

.lesson-item__num {
    font-size: 13px;
    font-weight: 600;
    font-variant-numeric: tabular-nums;
    color: var(--c-text-3);
    flex-shrink: 0;
    width: 24px;
    transition: color var(--ease);
}

.lesson-item__body {
    flex: 1;
    min-width: 0;
}

.lesson-item__title {
    font-size: 16px;
    font-weight: 500;
    color: var(--c-text);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    display: flex;
    align-items: center;
    gap: 8px;
}

.lesson-item__badge {
    display: inline-flex;
    align-items: center;
    padding: 2px 8px;
    background: var(--c-accent);
    color: #FFFFFF;
    font-size: 10px;
    font-weight: 700;
    letter-spacing: 0.5px;
    border-radius: 3px;
    white-space: nowrap;
    flex-shrink: 0;
}

.lesson-item__desc {
    margin-top: 2px;
    font-size: 13px;
    color: var(--c-text-2);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.lesson-item__arrow {
    width: 18px;
    height: 18px;
    color: var(--c-accent);
    flex-shrink: 0;
    opacity: 0;
    transition: opacity var(--ease), transform var(--ease);
}

/* 5. Empty State
   ===================================================== */
.empty-state {
    text-align: center;
    padding: 80px 24px;
}

.empty-state__icon {
    width: 56px;
    height: 56px;
    color: var(--c-border);
    margin: 0 auto 20px;
}

.empty-state__icon svg {
    width: 100%;
    height: 100%;
}

.empty-state__title {
    font-family: var(--font-serif);
    font-size: 22px;
    font-weight: 600;
    color: var(--c-text);
    margin-bottom: 8px;
}

.empty-state__desc {
    font-size: 15px;
    color: var(--c-text-2);
}

.empty-state__link {
    display: inline-block;
    margin-top: 20px;
    font-size: 14px;
    font-weight: 500;
    color: var(--c-accent);
    text-decoration: none;
}

.empty-state__link:hover {
    text-decoration: underline;
}

/* 6. Lesson Detail Page
   ===================================================== */
.lesson-detail-page {
    display: flex;
    min-height: calc(100vh - var(--header-h));
}

.lesson-detail-container {
    width: 100%;
}

.lesson-content-wrapper {
    display: flex;
    width: 100%;
    min-height: calc(100vh - var(--header-h));
}

/* Sidebar — see lesson-sidebar.css */

/* Content area */
.lesson-detail-content {
    flex: 1;
    min-width: 0;
    background: var(--c-bg);
    border-left: 1px solid var(--c-border);
    padding: 32px 40px;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.lesson-main-content {
    width: 100%;
    max-width: 860px;
}

/* 7. Markdown Content
   ===================================================== */
.markdown-content {
    width: 100%;
    font-size: 16px;
    line-height: 1.75;
    color: var(--c-text);
    background: var(--c-surface);
    border-radius: var(--radius-lg);
    padding: 40px 52px;
    box-shadow: 0 1px 2px rgba(0,0,0,.04), 0 4px 12px rgba(0,0,0,.03);
}

.markdown-content h1 {
    font-family: var(--font-serif);
    font-size: 34px;
    font-weight: 700;
    color: var(--c-text);
    margin: 0 0 20px;
    line-height: 1.25;
    letter-spacing: -0.02em;
    padding-bottom: 14px;
    border-bottom: 2px solid var(--c-border);
}

.markdown-content h2 {
    font-family: var(--font-serif);
    font-size: 26px;
    font-weight: 700;
    color: var(--c-text);
    margin: 40px 0 16px;
    line-height: 1.3;
    letter-spacing: -0.01em;
    padding-bottom: 8px;
    border-bottom: 1px solid var(--c-border-light);
}

.markdown-content h3 {
    font-size: 19px;
    font-weight: 600;
    color: var(--c-accent-dark);
    margin: 28px 0 12px;
    line-height: 1.4;
}

.markdown-content h4 {
    font-size: 16px;
    font-weight: 600;
    color: var(--c-text);
    margin: 24px 0 10px;
}

.markdown-content p {
    margin-bottom: 16px;
}

.markdown-content strong {
    font-weight: 600;
    color: var(--c-text);
}

.markdown-content em { font-style: italic; }

.markdown-content a {
    color: var(--c-accent);
    text-decoration: underline;
    text-underline-offset: 3px;
}

.markdown-content a:hover { color: var(--c-accent-dark); }

.markdown-content ul,
.markdown-content ol {
    padding-left: 24px;
    margin-bottom: 18px;
}

.markdown-content ul { list-style: disc; }
.markdown-content ol { list-style: decimal; }

.markdown-content li {
    margin-bottom: 6px;
    line-height: 1.65;
}

.markdown-content li::marker {
    color: var(--c-accent);
    font-weight: 600;
}

.markdown-content img {
    border-radius: var(--radius-lg);
    margin: 24px 0;
    box-shadow: 0 4px 16px rgba(0,0,0,.08);
}

.markdown-content code {
    font-family: var(--font-mono);
    font-size: 13.5px;
    background: var(--c-accent-bg);
    color: var(--c-accent-dark);
    padding: 2px 7px;
    border-radius: 5px;
    font-weight: 500;
}

.markdown-content pre {
    background: #1E293B;
    color: #E2E8F0;
    border-radius: var(--radius-lg);
    padding: 20px 24px;
    overflow-x: auto;
    margin: 24px 0;
    box-shadow: 0 4px 16px rgba(0,0,0,.12);
}

.markdown-content pre code {
    background: transparent;
    color: inherit;
    padding: 0;
    font-size: 13.5px;
    font-weight: 400;
}

.markdown-content blockquote {
    border-left: 3px solid var(--c-accent);
    background: var(--c-accent-bg);
    padding: 16px 20px;
    border-radius: 0 var(--radius) var(--radius) 0;
    margin: 24px 0;
    color: var(--c-text);
    font-style: italic;
}

.markdown-content hr { display: none; }

.markdown-content table {
    width: 100%;
    border-collapse: collapse;
    margin: 24px 0;
    border-radius: var(--radius);
    overflow: hidden;
    box-shadow: 0 1px 3px rgba(0,0,0,.06);
    font-size: 14px;
}

.markdown-content thead { background: var(--c-accent); color: #fff; }

.markdown-content th {
    padding: 12px 14px;
    text-align: left;
    font-weight: 600;
    font-size: 13px;
}

.markdown-content td {
    padding: 11px 14px;
    border-bottom: 1px solid var(--c-border-light);
}

.markdown-content tbody tr:last-child td { border-bottom: none; }
.markdown-content tbody tr:hover { background: var(--c-bg); }

/* KaTeX */
.markdown-content .katex { font-size: 1.05em; }

.markdown-content .katex-display {
    overflow-x: auto;
    overflow-y: hidden;
    margin: 24px 0;
    padding: 16px;
    background: var(--c-bg);
    border-radius: var(--radius);
}

/* Test button (at end of lesson) */
.lesson-end-actions {
    padding-top: 32px;
    border-top: 1px solid var(--c-border-light);
    display: flex;
    justify-content: center;
    margin-top: 16px;
}

.lesson-end-actions__nav {
    width: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 12px;
    flex-wrap: wrap;
}

.btn-open-test {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    padding: 14px 28px;
    background: var(--c-accent);
    color: #fff;
    border: none;
    border-radius: var(--radius-lg);
    font-size: 15px;
    font-weight: 600;
    font-family: inherit;
    cursor: pointer;
    transition: background var(--ease), transform var(--ease), box-shadow var(--ease);
    box-shadow: 0 4px 12px rgba(59,130,246,.25);
}

.btn-open-test:hover {
    background: var(--c-accent-dark);
    transform: translateY(-2px);
    box-shadow: 0 6px 16px rgba(59,130,246,.3);
}

.btn-open-test:active { transform: translateY(0); }

.btn-lesson-nav {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    padding: 14px 22px;
    background: #FFFFFF;
    color: var(--c-accent);
    border: 1px solid var(--c-border-light);
    border-radius: var(--radius-lg);
    font-size: 15px;
    font-weight: 600;
    font-family: inherit;
    text-decoration: none;
    cursor: pointer;
    transition: background var(--ease), transform var(--ease), box-shadow var(--ease), border-color var(--ease);
}

.btn-lesson-nav:hover {
    background: #F8FBFF;
    border-color: #BFDBFE;
    transform: translateY(-2px);
    box-shadow: 0 6px 16px rgba(59,130,246,.12);
}

.btn-lesson-nav:active { transform: translateY(0); }

.btn-lesson-nav--secondary {
    color: #374151;
}

.btn-lesson-nav svg {
    flex-shrink: 0;
}

/* 7. Search highlight
   ===================================================== */
.search-highlight {
    background: #FCD34D;
    color: inherit;
    border-radius: 3px;
    padding: 1px 3px;
    font-weight: 500;
}

/* 8. Pagination
   ===================================================== */
.pagination-wrapper {
    display: flex;
    justify-content: center;
    margin-top: 40px;
}

/* 9. Responsive
   ===================================================== */
@media (max-width: 1024px) {
    .lesson-detail-content {
        padding: 24px;
    }
    .markdown-content {
        padding: 32px 36px;
    }
}

@media (max-width: 768px) {
    .lessons-page { padding: 32px 16px 60px; }

    .lessons-header {
        flex-direction: column;
        align-items: flex-start;
        gap: 12px;
        margin-bottom: 24px;
        padding-bottom: 20px;
    }

    .lessons-header__title { font-size: 28px; }

    .lesson-item { gap: 14px; padding: 16px 12px; }
    .lesson-item__title { font-size: 15px; white-space: normal; }
    .lesson-item__badge { font-size: 9px; padding: 2px 6px; }
    .lesson-item__desc { display: none; }
    .lesson-item__arrow { opacity: 1; }

    .lesson-content-wrapper { flex-direction: column; }

    .lesson-detail-content {
        border-left: none;
        border-top: 1px solid var(--c-border);
        padding: 16px;
    }

    .markdown-content {
        padding: 20px 20px;
        border-radius: var(--radius);
    }

    .markdown-content h1 { font-size: 26px; }
    .markdown-content h2 { font-size: 21px; }
    .markdown-content h3 { font-size: 17px; }
    .lesson-end-actions__nav {
        flex-direction: column;
        align-items: stretch;
    }

    .btn-open-test,
    .btn-lesson-nav {
        width: 100%;
        justify-content: center;
    }
}

@media (max-width: 480px) {
    .markdown-content { padding: 16px; font-size: 15px; }
    .markdown-content h1 { font-size: 22px; }
    .markdown-content h2 { font-size: 19px; }
}