/* Design System and Variables */
:root {
  --font-sans: 'Inter', system-ui, -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', monospace;

  /* Dark Theme Palette (Default) */
  --bg-app: #0b0f19;
  --bg-card: #131a2b;
  --bg-card-header: #1c263d;
  --bg-editor: #0f1420;
  --border-color: #222e4c;
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  
  /* Brand/Accents */
  --color-primary: #3b82f6;      /* Blue */
  --color-primary-glow: rgba(59, 130, 246, 0.15);
  --color-accent: #a855f7;       /* Purple */
  --color-accent-glow: rgba(168, 85, 247, 0.25);
  --color-success: #10b981;      /* Emerald Green */
  --color-success-glow: rgba(16, 185, 129, 0.2);
  --color-warning: #f59e0b;      /* Amber */
  --color-danger: #ef4444;       /* Rose Red */
  
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.2), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  
  --border-radius-sm: 6px;
  --border-radius-md: 12px;
  --border-radius-lg: 16px;
  
  --transition-fast: 0.15s ease;
  --transition-normal: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Light Theme overrides */
body.light-mode {
  --bg-app: #f8fafc;
  --bg-card: #ffffff;
  --bg-card-header: #f1f5f9;
  --bg-editor: #fafafa;
  --border-color: #e2e8f0;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #94a3b8;
  
  --color-primary-glow: rgba(59, 130, 246, 0.08);
  --color-accent-glow: rgba(168, 85, 247, 0.08);
  --color-success-glow: rgba(16, 185, 129, 0.08);
}

/* Reset & Globals */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-app);
  color: var(--text-primary);
  height: 100vh;
  overflow: hidden;
  transition: background-color var(--transition-normal), color var(--transition-normal);
  line-height: 1.5;
}

/* App Layout */
.app-container {
  display: flex;
  flex-direction: column;
  height: 100vh;
}

/* Header */
.app-header {
  height: 64px;
  background-color: var(--bg-card);
  border-bottom: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0 24px;
  z-index: 10;
  box-shadow: var(--shadow-sm);
  transition: background-color var(--transition-normal), border-color var(--transition-normal);
}

.logo-area {
  display: flex;
  align-items: center;
  gap: 12px;
}

.logo-icon {
  filter: drop-shadow(0 2px 8px var(--color-primary-glow));
}

.logo-text {
  font-size: 20px;
  font-weight: 700;
  background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  letter-spacing: -0.5px;
}

.header-center {
  flex: 1;
  max-width: 480px;
  margin: 0 32px;
}

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

.progress-bar-container {
  height: 8px;
  background-color: var(--border-color);
  border-radius: 999px;
  overflow: hidden;
}

.progress-bar {
  height: 100%;
  background: linear-gradient(90deg, var(--color-primary), var(--color-accent));
  border-radius: 999px;
  width: 0%;
  transition: width 0.5s cubic-bezier(0.4, 0, 0.2, 1);
  box-shadow: 0 0 10px var(--color-primary-glow);
}

.progress-text {
  font-size: 11px;
  color: var(--text-secondary);
  font-weight: 500;
  text-align: right;
}

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

.xp-badge {
  background: linear-gradient(135deg, rgba(245, 158, 11, 0.15), rgba(239, 68, 68, 0.15));
  border: 1px solid rgba(245, 158, 11, 0.3);
  color: var(--color-warning);
  padding: 6px 12px;
  border-radius: 999px;
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 0.5px;
  box-shadow: 0 2px 8px rgba(245, 158, 11, 0.05);
}

.btn-icon {
  background: none;
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  width: 38px;
  height: 38px;
  border-radius: var(--border-radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.btn-icon:hover {
  background-color: var(--bg-card-header);
  color: var(--text-primary);
  border-color: var(--text-muted);
}

/* Workspace Panels Layout */
.workspace-layout {
  display: grid;
  grid-template-columns: 280px 1fr 1.2fr;
  flex: 1;
  overflow: hidden;
  height: calc(100vh - 64px);
}

/* Sidebar / Lesson Navigation */
.sidebar {
  background-color: var(--bg-card);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  overflow: hidden;
  transition: background-color var(--transition-normal), border-color var(--transition-normal);
}

.sidebar-header {
  padding: 20px 24px 12px;
}

.sidebar-header h3 {
  font-size: 14px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--text-muted);
}

.lesson-list {
  flex: 1;
  overflow-y: auto;
  padding: 0 12px 20px;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.lesson-item {
  display: flex;
  align-items: center;
  padding: 12px 16px;
  border-radius: var(--border-radius-sm);
  cursor: pointer;
  transition: all var(--transition-fast);
  color: var(--text-secondary);
  text-decoration: none;
  border: 1px solid transparent;
  gap: 12px;
}

.lesson-item:hover {
  background-color: var(--bg-card-header);
  color: var(--text-primary);
}

.lesson-item.active {
  background-color: var(--color-primary-glow);
  border-color: rgba(59, 130, 246, 0.3);
  color: var(--color-primary);
  font-weight: 600;
}

.lesson-item.completed .status-circle {
  background-color: var(--color-success);
  border-color: var(--color-success);
}

.lesson-item.completed .status-circle::after {
  content: "✓";
  color: white;
  font-size: 9px;
  display: block;
  text-align: center;
  line-height: 12px;
}

.status-circle {
  width: 14px;
  height: 14px;
  border-radius: 50%;
  border: 2px solid var(--text-muted);
  flex-shrink: 0;
  transition: all var(--transition-fast);
}

.lesson-title-text {
  font-size: 13.5px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.sidebar-footer {
  padding: 16px 20px;
  border-top: 1px solid var(--border-color);
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 13.5px;
  padding: 10px 16px;
  border-radius: var(--border-radius-sm);
  border: 1px solid transparent;
  cursor: pointer;
  transition: all var(--transition-fast);
  user-select: none;
}

.w-full {
  width: 100%;
}

.btn-sm {
  padding: 6px 12px;
  font-size: 12.5px;
}

.btn-primary {
  background-color: var(--color-primary);
  color: white;
  box-shadow: 0 4px 12px var(--color-primary-glow);
}

.btn-primary:hover:not(:disabled) {
  background-color: #2563eb;
  transform: translateY(-1px);
}

.btn-secondary {
  background-color: var(--bg-card-header);
  border-color: var(--border-color);
  color: var(--text-primary);
}

.btn-secondary:hover:not(:disabled) {
  background-color: var(--border-color);
}

.btn-accent {
  background: linear-gradient(135deg, var(--color-accent), #8b5cf6);
  color: white;
  box-shadow: 0 4px 12px var(--color-accent-glow);
}

.btn-accent:hover:not(:disabled) {
  opacity: 0.95;
  transform: translateY(-1px);
}

.btn-success {
  background-color: var(--color-success);
  color: white;
  box-shadow: 0 4px 12px var(--color-success-glow);
}

.btn-success:hover:not(:disabled) {
  background-color: #059669;
  transform: translateY(-1px);
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

/* Lesson Panel (Left Column) */
.lesson-panel {
  display: flex;
  flex-direction: column;
  background-color: var(--bg-app);
  border-right: 1px solid var(--border-color);
  overflow: hidden;
}

.panel-header {
  padding: 24px 30px;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.badge {
  align-self: flex-start;
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  padding: 4px 8px;
  border-radius: 4px;
  background-color: var(--color-primary-glow);
  color: var(--color-primary);
}

.panel-header h2 {
  font-size: 22px;
  font-weight: 700;
  letter-spacing: -0.5px;
}

.panel-body {
  flex: 1;
  overflow-y: auto;
  padding: 24px 30px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.lesson-content {
  color: var(--text-secondary);
  font-size: 14.5px;
  line-height: 1.6;
}

.lesson-content p {
  margin-bottom: 14px;
}

.lesson-content pre {
  background-color: var(--bg-editor);
  border: 1px solid var(--border-color);
  padding: 12px 16px;
  border-radius: var(--border-radius-sm);
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 13px;
  margin: 12px 0;
  color: #a5f3fc;
}

.lesson-content code:not(pre code) {
  font-family: var(--font-mono);
  background-color: var(--bg-card-header);
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 13px;
  color: #f472b6;
}

.lesson-content ul {
  margin: 12px 0 16px 20px;
}

.lesson-content li {
  margin-bottom: 6px;
}

/* Challenge Box */
.challenge-box {
  background: linear-gradient(135deg, rgba(59, 130, 246, 0.05), rgba(168, 85, 247, 0.05));
  border: 1px solid rgba(59, 130, 246, 0.25);
  border-radius: var(--border-radius-md);
  padding: 20px;
  box-shadow: var(--shadow-sm);
}

.challenge-box h4 {
  font-size: 14px;
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: 10px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

#challengeInstructions {
  font-size: 13.5px;
  color: var(--text-primary);
  line-height: 1.5;
}

#challengeInstructions p {
  margin-bottom: 8px;
}

#challengeInstructions code {
  font-family: var(--font-mono);
  background-color: rgba(59, 130, 246, 0.1);
  padding: 2px 5px;
  border-radius: 4px;
  color: var(--color-primary);
  font-size: 12.5px;
}

.panel-footer {
  padding: 20px 30px;
  border-top: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  background-color: var(--bg-card);
}

/* Coding Panel (Right Column) */
.coding-panel {
  display: flex;
  flex-direction: column;
  height: 100%;
  overflow: hidden;
}

/* Editor Section */
.editor-card {
  flex: 1.3;
  display: flex;
  flex-direction: column;
  background-color: var(--bg-editor);
  border-bottom: 1px solid var(--border-color);
  overflow: hidden;
}

.editor-header {
  height: 48px;
  background-color: var(--bg-card-header);
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 16px;
}

.tab-title {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  font-weight: 600;
  color: var(--text-primary);
}

.file-icon {
  color: var(--color-primary);
}

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

.editor-workspace {
  flex: 1;
  display: flex;
  position: relative;
  overflow: hidden;
}

.line-numbers {
  width: 48px;
  background-color: rgba(0, 0, 0, 0.15);
  border-right: 1px solid var(--border-color);
  padding: 16px 8px 16px 0;
  text-align: right;
  font-family: var(--font-mono);
  font-size: 13.5px;
  color: var(--text-muted);
  user-select: none;
  line-height: 1.6;
}

#codeEditor {
  flex: 1;
  background: transparent;
  border: none;
  outline: none;
  resize: none;
  font-family: var(--font-mono);
  font-size: 13.5px;
  color: #e2e8f0;
  padding: 16px;
  line-height: 1.6;
  white-space: pre;
  tab-size: 4;
}

/* Terminal/Console Section */
.terminal-card {
  flex: 1;
  display: flex;
  flex-direction: column;
  background-color: #060913;
  overflow: hidden;
}

.terminal-header {
  height: 40px;
  background-color: #0b0f1a;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 16px;
  font-size: 12px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--text-secondary);
}

.terminal-body {
  flex: 1;
  padding: 16px;
  overflow-y: auto;
  font-family: var(--font-mono);
  font-size: 13px;
  line-height: 1.6;
}

.console-line {
  margin-bottom: 4px;
  word-break: break-all;
  white-space: pre-wrap;
}

.console-line.input {
  color: var(--text-secondary);
}
.console-line.input::before {
  content: ">>> ";
  color: var(--color-primary);
  font-weight: bold;
}

.console-line.stdout {
  color: #e2e8f0;
}

.console-line.stderr {
  color: var(--color-danger);
}

.console-line.system-msg {
  color: var(--color-accent);
  font-style: italic;
}

.console-line.success-msg {
  color: var(--color-success);
  font-weight: bold;
}

/* Scrollbar Customization */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: transparent;
}

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

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

/* Responsive Grid Adapting */
@media (max-width: 1024px) {
  .workspace-layout {
    grid-template-columns: 240px 1fr;
    grid-template-rows: 1fr 1fr;
  }
  .lesson-panel {
    grid-column: 1 / 3;
    grid-row: 1 / 2;
    border-bottom: 1px solid var(--border-color);
  }
  .coding-panel {
    grid-column: 2 / 3;
    grid-row: 2 / 3;
  }
  .sidebar {
    grid-column: 1 / 2;
    grid-row: 2 / 3;
  }
}

/* Hints Styles */
.hints-container {
  margin-top: 14px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.hint-line {
  background-color: rgba(245, 158, 11, 0.08);
  border-left: 3px solid var(--color-warning);
  padding: 10px 14px;
  border-radius: 0 6px 6px 0;
  font-size: 13.2px;
  color: var(--text-primary);
  line-height: 1.4;
  animation: slideDown 0.22s cubic-bezier(0, 0, 0.2, 1);
}

body.light-mode .hint-line {
  background-color: rgba(245, 158, 11, 0.05);
}

@keyframes slideDown {
  from {
    opacity: 0;
    transform: translateY(-6px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}