:root {
  --bg-primary: #0a0d14;
  --bg-secondary: #121824;
  --bg-tertiary: #1a2332;
  --border-color: rgba(255, 255, 255, 0.08);
  --border-color-glow: rgba(245, 158, 11, 0.3);
  
  --text-primary: #f3f4f6;
  --text-secondary: #9ca3af;
  --text-muted: #4e5666;
  
  --accent-blue: #f97316;      /* Orange theme */
  --accent-emerald: #f59e0b;   /* Amber theme */
  --accent-amber: #eab308;
  --accent-rose: #f43f5e;
  --accent-terminal: #f59e0b;
  
  --font-sans: 'Inter', system-ui, -apple-system, sans-serif;
  --font-mono: 'Fira Code', 'Courier New', Courier, monospace;
}

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

body {
  font-family: var(--font-sans);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  min-height: 100vh;
  display: flex;
  overflow: hidden;
}

/* Scrollbar Customization */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}
::-webkit-scrollbar-track {
  background: transparent;
}
::-webkit-scrollbar-thumb {
  background: rgba(255, 255, 255, 0.08);
  border-radius: 4px;
}
::-webkit-scrollbar-thumb:hover {
  background: rgba(255, 255, 255, 0.15);
}

/* Sidebar Styling */
.sidebar {
  width: 320px;
  background-color: var(--bg-secondary);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  height: 100vh;
  z-index: 10;
  position: fixed;
  left: 0;
  top: 0;
  bottom: 0;
  transform: translateX(-100%);
  transition: transform 0.3s ease;
  box-shadow: 0 0 40px rgba(0, 0, 0, 0.5);
}

.sidebar.show {
  transform: translateX(0);
}

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

.sidebar-title {
  font-size: 1.25rem;
  font-weight: 800;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: 10px;
}

.sidebar-title span {
  color: var(--accent-emerald);
}

.sidebar-subtitle {
  font-size: 0.75rem;
  color: var(--text-secondary);
  margin-top: 4px;
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

.lesson-list {
  flex: 1;
  overflow-y: auto;
  padding: 16px 12px;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.lesson-item {
  width: 100%;
  padding: 12px 16px;
  border-radius: 8px;
  background: transparent;
  border: 1px solid transparent;
  color: var(--text-secondary);
  text-align: left;
  cursor: pointer;
  transition: all 0.2s ease;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.lesson-item:hover {
  background-color: rgba(255, 255, 255, 0.03);
  color: var(--text-primary);
}

.lesson-item.active {
  background-color: rgba(245, 158, 11, 0.1);
  border-color: rgba(245, 158, 11, 0.3);
  color: var(--text-primary);
}

.lesson-item.completed {
  border-left: 3px solid var(--accent-emerald);
}

.lesson-item-meta {
  font-size: 0.7rem;
  color: var(--accent-blue);
  text-transform: uppercase;
  font-weight: 700;
  letter-spacing: 0.05em;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.lesson-item-meta .check-icon {
  color: var(--accent-emerald);
  display: none;
}

.lesson-item.completed .check-icon {
  display: inline;
}

.lesson-item-title {
  font-size: 0.9rem;
  font-weight: 600;
  line-height: 1.4;
}

.sidebar-footer {
  padding: 20px;
  border-top: 1px solid var(--border-color);
  background-color: rgba(0, 0, 0, 0.2);
}

.progress-container {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.progress-header {
  display: flex;
  justify-content: space-between;
  font-size: 0.75rem;
  color: var(--text-secondary);
}

.progress-bar-bg {
  width: 100%;
  height: 6px;
  background-color: var(--bg-tertiary);
  border-radius: 3px;
  overflow: hidden;
}

.progress-bar-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent-blue), var(--accent-emerald));
  width: 0%;
  transition: width 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Main Content Styling */
.main-content {
  flex: 1;
  display: flex;
  flex-direction: column;
  height: 100vh;
  overflow: hidden;
  background-color: var(--bg-primary);
}

.main-header {
  height: 70px;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 32px;
  background-color: rgba(18, 24, 36, 0.5);
  backdrop-filter: blur(8px);
}

.menu-toggle {
  display: block;
  background: transparent;
  border: none;
  color: var(--text-primary);
  font-size: 1.5rem;
  cursor: pointer;
}

.header-actions {
  display: flex;
  gap: 12px;
}

.btn {
  padding: 8px 16px;
  border-radius: 6px;
  font-size: 0.875rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s ease;
  border: 1px solid transparent;
  display: flex;
  align-items: center;
  gap: 8px;
}

.btn-primary {
  background-color: var(--accent-blue);
  color: white;
}

.btn-primary:hover {
  background-color: #ea580c;
  box-shadow: 0 0 12px rgba(249, 115, 22, 0.4);
}

.btn-secondary {
  background-color: transparent;
  border-color: var(--border-color);
  color: var(--text-secondary);
}

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

/* Workspace Panels */
.workspace {
  flex: 1;
  display: grid;
  grid-template-columns: 550px 1fr;
  min-height: 0;
  overflow: hidden;
}

.panel {
  display: flex;
  flex-direction: column;
  height: 100%;
  overflow: hidden;
  position: relative;
}

.panel-left {
  border-right: 1px solid var(--border-color);
  background-color: var(--bg-primary);
}

.panel-right {
  background-color: #0b0f17;
}

.panel-header {
  padding: 16px 24px;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  background-color: rgba(18, 24, 36, 0.3);
}

.panel-title {
  font-size: 0.875rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  gap: 8px;
}

.panel-body {
  flex: 1;
  overflow-y: auto;
  padding: 32px;
}

/* Learning Content Styling */
.content-text {
  line-height: 1.7;
  font-size: 1rem;
  color: var(--text-primary);
}

.content-text h2 {
  font-size: 1.4rem;
  margin-top: 32px;
  margin-bottom: 16px;
  color: var(--text-primary);
  border-left: 4px solid var(--accent-blue);
  padding-left: 12px;
}

.content-text h3 {
  font-size: 1.1rem;
  margin-top: 24px;
  margin-bottom: 12px;
  color: var(--text-primary);
}

.content-text p {
  margin-bottom: 16px;
  color: #d1d5db;
}

.content-text ul, .content-text ol {
  margin-bottom: 20px;
  padding-left: 24px;
}

.content-text li {
  margin-bottom: 8px;
  color: #d1d5db;
}

.content-text code {
  font-family: var(--font-mono);
  background-color: rgba(255, 255, 255, 0.06);
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 0.9em;
  color: var(--accent-amber);
}

.content-text table {
  width: 100%;
  border-collapse: collapse;
  margin-bottom: 24px;
  font-size: 0.85rem;
}

.content-text th, .content-text td {
  border: 1px solid var(--border-color);
  padding: 10px 14px;
  text-align: left;
}

.content-text th {
  background-color: rgba(255, 255, 255, 0.02);
  font-weight: 700;
  color: var(--text-primary);
}

.content-text td {
  color: var(--text-secondary);
}

.content-text blockquote {
  border-left: 4px solid var(--accent-emerald);
  background-color: rgba(245, 158, 11, 0.05);
  padding: 16px 20px;
  margin-bottom: 24px;
  border-radius: 0 8px 8px 0;
}

.content-text blockquote p {
  margin-bottom: 0;
  color: #fed7aa;
  font-weight: 500;
}

.content-text pre {
  background-color: #080c14;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 16px;
  margin-bottom: 24px;
  overflow-x: auto;
}

.content-text pre code {
  background-color: transparent;
  padding: 0;
  color: #e6edf3;
  font-size: 0.85rem;
}

/* Syntax Highlighting */
.keyword { color: #ff7b72; font-weight: bold; }
.string { color: #a5d6ff; }
.comment { color: #8b949e; font-style: italic; }
.function { color: #ffa657; }
.variable { color: #79c0ff; }
.number { color: #79c0ff; }
.boolean { color: #79c0ff; }
.type { color: #ff7b72; }

/* Interactive Code Editor (Execute Program Style) */
.editor-header {
  height: 48px;
  background-color: #121824;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0 16px;
}

.editor-tabs {
  display: flex;
  gap: 4px;
  height: 100%;
}

.editor-tab {
  height: 100%;
  padding: 0 16px;
  display: flex;
  align-items: center;
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--text-secondary);
  border-right: 1px solid var(--border-color);
  background-color: transparent;
  user-select: none;
}

.editor-tab.active {
  background-color: #0b0f17;
  color: var(--text-primary);
  border-bottom: 2px solid var(--accent-blue);
  font-weight: 600;
}

.btn-run {
  background-color: var(--accent-emerald);
  color: #080c14;
  padding: 6px 14px;
  border-radius: 4px;
  font-size: 0.8rem;
  font-weight: 700;
  border: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 6px;
  transition: all 0.2s ease;
}

.btn-run:hover {
  background-color: #fbbf24;
  box-shadow: 0 0 10px rgba(245, 158, 11, 0.4);
}

.editor-container {
  flex: 1;
  display: flex;
  overflow: hidden;
  background-color: #0b0f17;
  position: relative;
}

.editor-gutter {
  width: 48px;
  background-color: #080c12;
  border-right: 1px solid var(--border-color);
  padding: 16px 0;
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  padding-right: 12px;
  color: var(--text-muted);
  font-family: var(--font-mono);
  font-size: 0.8rem;
  line-height: 1.6;
  user-select: none;
}

.editor-textarea {
  flex: 1;
  height: 100%;
  background: transparent;
  border: none;
  resize: none;
  outline: none;
  color: var(--text-primary);
  font-family: var(--font-mono);
  font-size: 0.825rem;
  line-height: 1.6;
  padding: 16px;
  tab-size: 4; /* Standard RF spacing is 4 spaces */
  overflow: auto;
  white-space: pre;
}

/* Terminal Area */
.terminal-panel {
  height: 240px;
  background-color: #07090e;
  border-top: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
}

.terminal-header {
  padding: 8px 16px;
  background-color: #0a0d14;
  border-bottom: 1px solid var(--border-color);
  font-size: 0.725rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  gap: 8px;
}

.terminal-body {
  flex: 1;
  padding: 16px;
  overflow-y: auto;
  font-family: var(--font-mono);
  font-size: 0.775rem;
  line-height: 1.6;
}

.terminal-line {
  margin-bottom: 4px;
}

.terminal-line.success {
  color: var(--accent-emerald);
}

.terminal-line.error {
  color: var(--accent-rose);
}

.terminal-line.info {
  color: var(--accent-blue);
}

.terminal-line.warn {
  color: var(--accent-amber);
}

.terminal-line.text-muted {
  color: var(--text-muted);
}

/* Next Lesson overlay layout (glassmorphism) */
.lesson-overlay {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: rgba(10, 13, 20, 0.85);
  backdrop-filter: blur(4px);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 5;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.3s ease;
}

.lesson-overlay.show {
  opacity: 1;
  pointer-events: auto;
}

.overlay-card {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color-glow);
  padding: 40px;
  border-radius: 16px;
  text-align: center;
  max-width: 420px;
  box-shadow: 0 20px 40px -15px rgba(0, 0, 0, 0.6);
  transform: translateY(20px);
  transition: transform 0.3s cubic-bezier(0.34, 1.56, 0.64, 1);
}

.lesson-overlay.show .overlay-card {
  transform: translateY(0);
}

.overlay-icon {
  font-size: 3.5rem;
  margin-bottom: 16px;
  animation: bounce 1s infinite alternate;
}

.overlay-title {
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--accent-emerald);
  margin-bottom: 12px;
}

.overlay-desc {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: 28px;
}

@keyframes bounce {
  from { transform: translateY(0); }
  to { transform: translateY(-10px); }
}

/* Responsive adjustments */
@media (max-width: 1100px) {
  .workspace {
    grid-template-columns: 1fr;
    grid-template-rows: 1fr 1fr;
    overflow-y: auto;
  }
  .panel-left {
    border-right: none;
    border-bottom: 1px solid var(--border-color);
  }
}

@media (max-width: 768px) {
  .sidebar {
    width: 280px;
  }
  .main-header {
    padding: 0 16px;
  }
  .panel-body {
    padding: 20px;
  }
}

@media (max-width: 480px) {
  .sidebar {
    width: 85vw;
    max-width: 300px;
  }
  .main-header {
    height: auto;
    min-height: 60px;
    flex-wrap: wrap;
    gap: 8px;
    padding: 10px 12px;
  }
  #current-lesson-title {
    font-size: 1rem;
    max-width: 60vw;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
  }
  .header-actions {
    width: 100%;
    justify-content: flex-end;
  }
  .header-actions .btn {
    padding: 6px 10px;
    font-size: 0.75rem;
  }
  .panel-body {
    padding: 16px;
  }
  .editor-header {
    height: auto;
    flex-wrap: wrap;
    gap: 8px;
    padding: 8px 12px;
  }
  /* .editor-tab/.editor-tabs default to height:100% of .editor-header - fine when
     the header is a fixed 48px, but once the header wraps to height:auto that 100%
     has no definite base to resolve against, so the browser under-sizes the header
     box and the wrapped 2nd row (editor-actions) renders outside it, painted over
     by .editor-container right after. Break the % dependency on mobile. */
  .editor-tabs,
  .editor-tab {
    height: auto;
  }
  .editor-tab {
    padding: 10px 16px;
  }
  .editor-actions {
    flex-wrap: wrap;
    width: 100%;
  }
  .editor-actions .btn {
    padding: 6px 10px;
    font-size: 0.75rem;
  }
  .menu-toggle {
    min-width: 44px;
    min-height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
  }
  .editor-textarea {
    font-size: 16px;
  }
  .terminal-panel {
    height: 160px;
  }
  .content-text table {
    display: block;
    overflow-x: auto;
    white-space: nowrap;
  }
  .overlay-card {
    padding: 24px;
    max-width: 90vw;
  }
}

/* Content blocks for structured learning */
.content-block {
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 20px;
  margin-bottom: 24px;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}
.content-block.theory {
  border-left: 4px solid var(--accent-blue);
}
.content-block.example {
  border-left: 4px solid var(--accent-amber);
}
.content-block.task {
  border-left: 4px solid var(--accent-emerald);
  background: rgba(16, 185, 129, 0.03);
}
.content-block-title {
  font-weight: 700;
  font-size: 0.95rem;
  margin-bottom: 12px;
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--text-primary);
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
  padding-bottom: 8px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.editor-actions {
  display: flex;
  gap: 8px;
  align-items: center;
}

.btn-hint, .btn-solution {
  transition: all 0.2s ease;
}

.btn-hint:hover {
  background-color: rgba(255, 255, 255, 0.1) !important;
  color: var(--text-primary) !important;
  box-shadow: 0 0 8px rgba(255, 255, 255, 0.1);
}

.btn-solution:hover {
  background-color: rgba(255, 255, 255, 0.1) !important;
  color: var(--text-primary) !important;
  box-shadow: 0 0 8px rgba(255, 255, 255, 0.1);
}


/* XP toast (lesson completion feedback) */
.xp-toast {
  position: fixed;
  bottom: 24px;
  right: 24px;
  background-color: var(--accent-amber);
  color: #1a1400;
  font-weight: 700;
  font-size: 0.95rem;
  padding: 10px 20px;
  border-radius: 9999px;
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
  z-index: 9999;
  animation: xp-toast-in 0.3s ease;
}

.xp-toast-out {
  animation: xp-toast-fade 0.4s ease forwards;
}

@keyframes xp-toast-in {
  from { transform: translateY(20px); opacity: 0; }
  to { transform: translateY(0); opacity: 1; }
}

@keyframes xp-toast-fade {
  to { opacity: 0; transform: translateY(-10px); }
}