/* ─── LESSON PAGE LAYOUT ─── */

/* Fixed left sidebar + fixed right TOC + scrollable center */
.lesson-layout {
  display: flex;
  min-height: 100vh;
  padding-top: 65px; /* nav height */
}

/* ─── LEFT SIDEBAR ─── */
.lesson-sidebar {
  position: fixed;
  top: 65px;
  right: 0;
  width: 260px;
  height: calc(100vh - 65px);
  overflow-y: auto;
  background: var(--bg-secondary);
  border-left: 1px solid var(--border);
  z-index: 10;
  scrollbar-width: thin;
  scrollbar-color: var(--border) transparent;
}

.sidebar-header {
  padding: 24px 20px 18px;
  border-bottom: 1px solid var(--border);
}

.sidebar-title {
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--text-muted);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin-bottom: 12px;
}

.sidebar-progress {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.progress-bar {
  height: 4px;
  background: var(--border);
  border-radius: 2px;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent), var(--accent-secondary));
  border-radius: 2px;
  transition: width 0.5s ease;
}

.progress-label {
  font-size: 0.72rem;
  color: var(--text-muted);
}

.sidebar-nav {
  display: flex;
  flex-direction: row;
  padding: 8px 0;
}

.sidebar-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 11px 20px;
  text-decoration: none;
  color: var(--text-secondary);
  font-size: 0.85rem;
  transition: all 0.2s ease;
  border-right: 3px solid transparent;
}

.sidebar-item:hover {
  color: var(--text-primary);
  background: rgba(59,130,246,0.05);
}

.sidebar-item.active {
  color: var(--accent-light);
  background: rgba(59,130,246,0.08);
  border-right-color: var(--accent);
  font-weight: 600;
}

.sidebar-item.locked {
  opacity: 0.4;
  cursor: not-allowed;
  pointer-events: none;
}

.sidebar-num {
  width: 26px;
  height: 26px;
  border-radius: 7px;
  background: var(--bg-primary);
  border: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.72rem;
  font-weight: 700;
  flex-shrink: 0;
  color: var(--text-muted);
}

.sidebar-item.active .sidebar-num {
  background: var(--accent);
  border-color: var(--accent);
  color: white;
}

.sidebar-name { flex: 1; line-height: 1.3; }
.sidebar-check { color: var(--green); font-size: 0.8rem; flex-shrink: 0; }
.sidebar-lock  { font-size: 0.7rem; flex-shrink: 0; }

/* ─── MAIN CONTENT ─── */
.lesson-main {
  flex: 1;
  margin-right: 260px;  /* sidebar width */
  margin-left: 200px;   /* TOC width */
  padding: 40px 52px 100px;
  min-width: 0;
  max-width: 860px;
  width: 100%;
  /* center it in the remaining space */
  margin-left: auto;
  margin-right: 260px;
}

/* ─── BREADCRUMB ─── */
.breadcrumb {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-bottom: 28px;
}

.breadcrumb a {
  color: var(--text-muted);
  text-decoration: none;
  transition: color 0.2s;
}

.breadcrumb a:hover { color: var(--accent-light); }
.bc-sep { opacity: 0.4; }

/* ─── LESSON HEADER ─── */
.lesson-header {
  margin-bottom: 16px;
}

.lesson-meta-row {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 16px;
}

.lesson-tag {
  display: inline-flex;
  align-items: center;
  background: rgba(59,130,246,0.1);
  border: 1px solid rgba(59,130,246,0.25);
  color: var(--accent-light);
  font-size: 0.72rem;
  font-weight: 600;
  padding: 3px 12px;
  border-radius: 20px;
}

.lesson-tag-green { background: rgba(16,185,129,0.1); border-color: rgba(16,185,129,0.25); color: var(--green); }
.lesson-tag-purple { background: rgba(139,92,246,0.1); border-color: rgba(139,92,246,0.25); color: #a78bfa; }

.lesson-title {
  font-size: clamp(1.6rem, 2.5vw, 2.1rem);
  font-weight: 900;
  letter-spacing: -0.03em;
  line-height: 1.25;
  margin-bottom: 14px;
}

.lesson-lead {
  color: var(--text-secondary);
  font-size: 1rem;
  line-height: 1.8;
  margin-bottom: 24px;
}

.lesson-instructor-row {
  display: flex;
  align-items: center;
  gap: 12px;
}

.lesson-avatar {
  width: 38px;
  height: 38px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--accent), var(--python-yellow));
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.95rem;
  font-weight: 700;
  color: white;
  flex-shrink: 0;
}

.lesson-instructor-name { font-size: 0.875rem; font-weight: 600; }
.lesson-instructor-role { font-size: 0.72rem; color: var(--text-muted); }

/* ─── SECTION LABEL ─── */
.lesson-section {
  margin-bottom: 56px;
  scroll-margin-top: 88px;
}

.section-label {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 1.5rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  color: var(--text-primary);
  margin-bottom: 20px;
  padding-bottom: 12px;
}

.section-label-icon { font-size: 1.5rem; }

/* ─── VIDEO TABS ─── */
.video-tabs {
  display: flex;
  gap: 8px;
  margin-bottom: 16px;
}

.video-tab {
  background: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--text-secondary);
  padding: 7px 22px;
  border-radius: 30px;
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s ease;
  font-family: 'Vazirmatn', sans-serif;
}

.video-tab:hover { border-color: var(--accent); color: var(--accent-light); }

.video-tab.active {
  background: var(--accent);
  border-color: var(--accent);
  color: white;
  box-shadow: 0 0 16px var(--accent-glow);
}

.video-player-wrap { display: none; }
.video-player-wrap.active { display: block; }

.video-embed {
  position: relative;
  width: 100%;
  padding-top: 56.25%;
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--bg-card);
  border: 1px solid var(--border);
}

.video-embed iframe {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  border: none;
}

.video-caption {
  margin-top: 10px;
  font-size: 0.78rem;
  color: var(--text-muted);
  text-align: center;
}

.video-caption a { color: var(--accent-light); text-decoration: none; font-weight: 500; }
.video-caption a:hover { text-decoration: underline; }

/* ─── LESSON CONTENT ─── */
.lesson-content h2 {
  font-size: 1.15rem;
  font-weight: 700;
  margin: 32px 0 12px;
  color: var(--text-primary);
}

.lesson-content h2:first-child { margin-top: 0; }

.lesson-content p {
  color: var(--text-secondary);
  font-size: 0.95rem;
  line-height: 1.85;
  margin-bottom: 16px;
}

.lesson-content ul, .lesson-content ol {
  color: var(--text-secondary);
  font-size: 0.95rem;
  line-height: 1.85;
  padding-right: 24px;
  margin-bottom: 16px;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.lesson-content code {
  background: rgba(59,130,246,0.1);
  border: 1px solid rgba(59,130,246,0.2);
  color: var(--accent-light);
  padding: 2px 7px;
  border-radius: 5px;
  font-family: 'Courier New', monospace;
  font-size: 0.85em;
  direction: ltr;
  display: inline-block;
}

/* ─── CODE BLOCK ─── */
.code-block {
  background: #0d1117;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  margin: 20px 0;
  direction: ltr;
}

.code-block-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 18px;
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border);
}

.code-lang { font-size: 0.72rem; font-weight: 700; color: var(--python-yellow); letter-spacing: 0.05em; }

.copy-btn {
  background: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--text-muted);
  font-size: 0.72rem;
  padding: 3px 12px;
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.2s;
  font-family: 'Vazirmatn', sans-serif;
}

.copy-btn:hover { border-color: var(--accent); color: var(--accent-light); }
.copy-btn.copied { background: rgba(16,185,129,0.1); border-color: var(--green); color: var(--green); }

.code-block pre {
  padding: 20px;
  overflow-x: auto;
  margin: 0;
  font-family: 'Courier New', monospace;
  font-size: 0.875rem;
  line-height: 1.8;
}

.code-block code {
  background: none;
  border: none;
  color: var(--text-primary);
  padding: 0;
  font-size: inherit;
  direction: ltr;
}

/* ─── INFO BOXES ─── */
.info-box {
  display: flex;
  gap: 14px;
  padding: 16px 20px;
  border-radius: var(--radius-sm);
  margin: 20px 0;
  font-size: 0.9rem;
  line-height: 1.7;
}

.info-box-icon { font-size: 1.2rem; flex-shrink: 0; margin-top: 2px; }

.info-box-blue   { background: rgba(59,130,246,0.08); border: 1px solid rgba(59,130,246,0.25); color: var(--text-secondary); }
.info-box-blue strong { color: var(--accent-light); }
.info-box-yellow { background: rgba(255,212,59,0.06); border: 1px solid rgba(255,212,59,0.25); color: var(--text-secondary); }
.info-box-yellow strong { color: var(--python-yellow); }
.info-box-green  { background: rgba(16,185,129,0.06); border: 1px solid rgba(16,185,129,0.25); color: var(--text-secondary); }
.info-box-green strong { color: var(--green); }

/* ─── EXERCISES ─── */
.exercise-list {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.exercise-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  transition: border-color 0.2s;
}

.exercise-card:hover { border-color: var(--border-light); }

.exercise-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 12px;
}

.exercise-num { font-size: 0.78rem; font-weight: 700; color: var(--text-muted); letter-spacing: 0.05em; }

.exercise-level { font-size: 0.7rem; font-weight: 700; padding: 2px 10px; border-radius: 20px; }
.exercise-easy   { background: rgba(16,185,129,0.1); color: var(--green); border: 1px solid rgba(16,185,129,0.3); }
.exercise-medium { background: rgba(245,158,11,0.1); color: var(--orange); border: 1px solid rgba(245,158,11,0.3); }
.exercise-hard   { background: rgba(239,68,68,0.1); color: #f87171; border: 1px solid rgba(239,68,68,0.3); }

.exercise-desc {
  color: var(--text-secondary);
  font-size: 0.9rem;
  line-height: 1.75;
}

.exercise-desc code {
  background: rgba(59,130,246,0.1);
  border: 1px solid rgba(59,130,246,0.2);
  color: var(--accent-light);
  padding: 1px 6px;
  border-radius: 4px;
  font-family: 'Courier New', monospace;
  font-size: 0.85em;
  direction: ltr;
  display: inline-block;
}

.exercise-hint {
  margin-top: 16px;
  border-top: 1px solid var(--border);
  padding-top: 14px;
}

.exercise-hint summary {
  cursor: pointer;
  font-size: 0.85rem;
  color: var(--accent-light);
  font-weight: 600;
  user-select: none;
  list-style: none;
}

.exercise-hint summary::-webkit-details-marker { display: none; }

.hint-body {
  margin-top: 12px;
  background: #0d1117;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 16px;
  direction: ltr;
  overflow-x: auto;
}

.hint-body pre {
  font-family: 'Courier New', monospace;
  font-size: 0.85rem;
  line-height: 1.8;
  color: var(--text-primary);
  margin: 0;
}

/* ─── REFERENCES ─── */
.reference-list { display: flex; flex-direction: column; gap: 12px; }

.reference-card {
  display: flex;
  align-items: center;
  gap: 16px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px 20px;
  text-decoration: none;
  transition: all 0.2s ease;
}

.reference-card:hover { border-color: var(--accent); transform: translateX(-3px); }

.ref-icon {
  width: 44px;
  height: 44px;
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
  flex-shrink: 0;
}

.ref-icon-blue   { background: rgba(59,130,246,0.12); }
.ref-icon-green  { background: rgba(16,185,129,0.12); }
.ref-icon-yellow { background: rgba(255,212,59,0.12); }
.ref-icon-purple { background: rgba(139,92,246,0.12); }

.ref-body { flex: 1; }
.ref-title { font-size: 0.9rem; font-weight: 600; color: var(--text-primary); margin-bottom: 3px; }
.ref-desc  { font-size: 0.78rem; color: var(--text-muted); line-height: 1.5; }
.ref-arrow { color: var(--text-muted); font-size: 0.9rem; transition: color 0.2s, transform 0.2s; }
.reference-card:hover .ref-arrow { color: var(--accent-light); transform: translateX(-3px); }

/* ─── PREV / NEXT BUTTONS ─── */
.lesson-nav-btns {
  display: flex;
  gap: 12px;
  margin-top: 48px;
  padding-top: 32px;
  border-top: 1px solid var(--border);
}

.lesson-nav-btn {
  flex: 1;
  display: flex;
  align-items: center;
  gap: 14px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px 22px;
  text-decoration: none;
  transition: all 0.2s ease;
  color: var(--text-primary);
}

.lesson-nav-btn:hover { border-color: var(--accent); background: var(--bg-card-hover); }
.lesson-nav-btn.disabled { opacity: 0.3; pointer-events: none; }
.lesson-nav-next { justify-content: flex-end; }
.nav-btn-label { font-size: 0.7rem; color: var(--text-muted); font-weight: 600; letter-spacing: 0.05em; text-transform: uppercase; }
.nav-btn-title { font-size: 0.9rem; font-weight: 600; }

/* ─── RIGHT TOC ─── */
.lesson-toc {
  position: fixed;
  top: 65px;
  left: 0;            /* RTL: TOC on the left */
  width: 200px;
  height: calc(100vh - 65px);
  padding: 28px 20px;
  border-right: 1px solid var(--border);
  overflow-y: auto;
  background: var(--bg-secondary);
  z-index: 10;
}

.toc-title {
  font-size: 0.7rem;
  font-weight: 700;
  color: var(--text-muted);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin-bottom: 14px;
}

.toc-nav {
  display: flex;
  flex-direction: row;
  gap: 2px;
  margin-bottom: 28px;
}

.toc-link {
  display: block;
  font-size: 0.8rem;
  color: var(--text-muted);
  text-decoration: none;
  padding: 6px 10px;
  border-radius: 6px;
  transition: all 0.2s;
  border-right: 2px solid transparent;
  line-height: 1.4;
}

.toc-link:hover { color: var(--text-primary); background: rgba(59,130,246,0.06); }
.toc-link.active { color: var(--accent-light); border-right-color: var(--accent); background: rgba(59,130,246,0.06); }

.toc-donate-btn {
  display: block;
  text-align: center;
  background: rgba(255,212,59,0.08);
  border: 1px solid rgba(255,212,59,0.25);
  color: var(--python-yellow);
  font-size: 0.78rem;
  font-weight: 600;
  padding: 9px 12px;
  border-radius: 30px;
  text-decoration: none;
  transition: all 0.2s;
}

.toc-donate-btn:hover { background: rgba(255,212,59,0.14); box-shadow: 0 0 14px rgba(255,212,59,0.15); }

/* ─── RESPONSIVE ─── */
@media (max-width: 1200px) {
  .lesson-toc { display: none; }
  .lesson-main {
    margin-left: 0;
    margin-right: 260px;
    padding: 40px 40px 80px;
  }
}

@media (max-width: 780px) {
  .lesson-sidebar { display: none; }
  .lesson-main {
    margin-right: 0;
    margin-left: 0;
    padding: 28px 20px 60px;
    max-width: 100%;
  }
}