/* ============================================
   Tryngo Design System
   ============================================ */

/* CSS Custom Properties */
:root {
  /* Colors */
  --color-primary: #00ADD8;
  --color-primary-dark: #0096b8;
  --color-primary-light: #e6f7fc;
  --color-secondary: #E44D26;
  --color-secondary-dark: #c73e1d;
  --color-accent: #7c3aed;
  --color-bg: #ffffff;
  --color-bg-alt: #f8fafc;
  --color-bg-card: #ffffff;
  --color-text: #1a1a2e;
  --color-text-secondary: #475569;
  --color-text-muted: #94a3b8;
  --color-border: #e2e8f0;
  --color-border-light: #f1f5f9;
  --color-success: #10b981;
  --color-warning: #f59e0b;
  --color-error: #ef4444;
  --color-code-bg: #1e293b;
  --color-overlay: rgba(0, 0, 0, 0.5);

  /* Typography */
  --font-sans: 'Inter', system-ui, -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', monospace;
  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 2rem;
  --font-size-4xl: 2.5rem;
  --font-size-5xl: 3.5rem;
  --font-weight-normal: 400;
  --font-weight-medium: 500;
  --font-weight-semibold: 600;
  --font-weight-bold: 700;
  --font-weight-extrabold: 800;
  --line-height-tight: 1.2;
  --line-height-normal: 1.5;
  --line-height-relaxed: 1.75;

  /* Spacing */
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2rem;
  --spacing-2xl: 3rem;
  --spacing-3xl: 4rem;
  --spacing-4xl: 6rem;

  /* Border Radius */
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-full: 9999px;

  /* Shadows */
  --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 -2px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.1);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 8px 10px -6px rgba(0, 0, 0, 0.1);

  /* Layout */
  --container-max: 1280px;
  --container-narrow: 960px;
  --container-padding: var(--spacing-xl);
  --navbar-height: 4rem;
  --sidebar-width: 280px;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-normal: 250ms ease;
  --transition-slow: 350ms ease;
}

/* Reset & Base */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  font-size: var(--font-size-base);
  line-height: var(--line-height-normal);
  color: var(--color-text);
  background-color: var(--color-bg);
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

a {
  color: var(--color-primary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--color-primary-dark);
}

ul, ol {
  list-style: none;
}

button {
  cursor: pointer;
  font-family: inherit;
  border: none;
  background: none;
}

h1, h2, h3, h4, h5, h6 {
  line-height: var(--line-height-tight);
  color: var(--color-text);
}

code, pre {
  font-family: var(--font-mono);
}

/* ============================================
   Navbar
   ============================================ */

.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--navbar-height);
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--color-border);
  z-index: 1000;
}

.navbar-container {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--container-padding);
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.navbar-brand {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  font-size: var(--font-size-xl);
  font-weight: var(--font-weight-bold);
  color: var(--color-text);
  text-decoration: none;
}

.brand-icon {
  font-size: var(--font-size-2xl);
}

.brand-text {
  background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.navbar-links {
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
}

.nav-link {
  padding: var(--spacing-sm) var(--spacing-md);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--color-text-secondary);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
}

.nav-link:hover,
.nav-link.active {
  color: var(--color-primary);
  background: var(--color-primary-light);
}

.navbar-toggle {
  display: none;
  width: 2.5rem;
  height: 2.5rem;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-md);
  transition: background var(--transition-fast);
}

.navbar-toggle:hover {
  background: var(--color-bg-alt);
}

.hamburger,
.hamburger::before,
.hamburger::after {
  display: block;
  width: 1.25rem;
  height: 2px;
  background: var(--color-text);
  border-radius: 2px;
  transition: all var(--transition-normal);
  position: relative;
}

.hamburger::before,
.hamburger::after {
  content: '';
  position: absolute;
  left: 0;
}

.hamburger::before {
  top: -6px;
}

.hamburger::after {
  top: 6px;
}

.navbar-toggle[aria-expanded="true"] .hamburger {
  background: transparent;
}

.navbar-toggle[aria-expanded="true"] .hamburger::before {
  top: 0;
  transform: rotate(45deg);
}

.navbar-toggle[aria-expanded="true"] .hamburger::after {
  top: 0;
  transform: rotate(-45deg);
}

/* ============================================
   Main Content
   ============================================ */

.main-content {
  padding-top: var(--navbar-height);
  min-height: calc(100vh - var(--navbar-height));
}

/* ============================================
   Hero Section
   ============================================ */

.hero {
  padding: var(--spacing-4xl) var(--container-padding);
  text-align: center;
  background: linear-gradient(135deg, var(--color-primary-light) 0%, var(--color-bg) 50%, #f0f0ff 100%);
  position: relative;
  overflow: hidden;
}

.hero-content {
  max-width: var(--container-narrow);
  margin: 0 auto;
  position: relative;
  z-index: 1;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-sm);
  padding: var(--spacing-xs) var(--spacing-md);
  background: var(--color-primary);
  color: white;
  border-radius: var(--radius-full);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  margin-bottom: var(--spacing-xl);
}

.hero-title {
  font-size: var(--font-size-5xl);
  font-weight: var(--font-weight-extrabold);
  margin-bottom: var(--spacing-lg);
  line-height: var(--line-height-tight);
}

.hero-title .highlight {
  background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-subtitle {
  font-size: var(--font-size-xl);
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-2xl);
  line-height: var(--line-height-relaxed);
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

.hero-actions {
  display: flex;
  gap: var(--spacing-md);
  justify-content: center;
  flex-wrap: wrap;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-sm);
  padding: var(--spacing-md) var(--spacing-xl);
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-semibold);
  border-radius: var(--radius-lg);
  transition: all var(--transition-normal);
  text-decoration: none;
}

.btn-primary {
  background: var(--color-primary);
  color: white;
  box-shadow: var(--shadow-md);
}

.btn-primary:hover {
  background: var(--color-primary-dark);
  box-shadow: var(--shadow-lg);
  transform: translateY(-1px);
  color: white;
}

.btn-secondary {
  background: var(--color-bg);
  color: var(--color-text);
  border: 2px solid var(--color-border);
}

.btn-secondary:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
  transform: translateY(-1px);
}

.hero-decoration {
  position: absolute;
  width: 600px;
  height: 600px;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(0, 173, 216, 0.08) 0%, transparent 70%);
  top: -200px;
  right: -200px;
  pointer-events: none;
}

.hero-decoration-2 {
  position: absolute;
  width: 400px;
  height: 400px;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(124, 58, 237, 0.06) 0%, transparent 70%);
  bottom: -150px;
  left: -150px;
  pointer-events: none;
}

/* ============================================
   Languages Section (Cards with Search)
   ============================================ */

.languages-section {
  padding: var(--spacing-4xl) var(--container-padding);
  max-width: var(--container-max);
  margin: 0 auto;
}

.section-header {
  text-align: center;
  margin-bottom: var(--spacing-2xl);
}

.section-title {
  font-size: var(--font-size-3xl);
  font-weight: var(--font-weight-bold);
  margin-bottom: var(--spacing-sm);
}

.section-subtitle {
  font-size: var(--font-size-lg);
  color: var(--color-text-secondary);
}

.search-container {
  max-width: 480px;
  margin: var(--spacing-xl) auto;
  position: relative;
}

.search-input {
  width: 100%;
  padding: var(--spacing-md) var(--spacing-lg);
  padding-left: 3rem;
  font-size: var(--font-size-base);
  font-family: var(--font-sans);
  border: 2px solid var(--color-border);
  border-radius: var(--radius-lg);
  background: var(--color-bg);
  transition: all var(--transition-fast);
  color: var(--color-text);
}

.search-input:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(0, 173, 216, 0.1);
}

.search-icon {
  position: absolute;
  left: var(--spacing-md);
  top: 50%;
  transform: translateY(-50%);
  font-size: var(--font-size-lg);
  color: var(--color-text-muted);
  pointer-events: none;
}

.language-cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: var(--spacing-lg);
}

.language-card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  padding: var(--spacing-xl);
  transition: all var(--transition-normal);
  cursor: pointer;
  text-decoration: none;
  color: inherit;
  display: flex;
  flex-direction: column;
}

.language-card:hover {
  border-color: var(--color-primary);
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
  color: inherit;
}

.language-card-icon {
  font-size: 3rem;
  margin-bottom: var(--spacing-md);
}

.language-card-name {
  font-size: var(--font-size-xl);
  font-weight: var(--font-weight-bold);
  margin-bottom: var(--spacing-xs);
}

.language-card-desc {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  line-height: var(--line-height-relaxed);
  flex: 1;
}

.language-card-meta {
  display: flex;
  gap: var(--spacing-md);
  margin-top: var(--spacing-md);
  padding-top: var(--spacing-md);
  border-top: 1px solid var(--color-border-light);
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
}

.language-card-meta span {
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
}

.language-card[data-level]::before {
  content: attr(data-level);
  position: absolute;
  top: var(--spacing-sm);
  right: var(--spacing-sm);
  padding: var(--spacing-xs) var(--spacing-sm);
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-semibold);
  border-radius: var(--radius-full);
  text-transform: uppercase;
}

/* ============================================
   Dashboard Layout
   ============================================ */

.dashboard {
  display: grid;
  grid-template-columns: var(--sidebar-width) 1fr;
  min-height: calc(100vh - var(--navbar-height));
}

.dashboard-sidebar {
  background: var(--color-bg-alt);
  border-right: 1px solid var(--color-border);
  padding: var(--spacing-lg);
  position: sticky;
  top: var(--navbar-height);
  height: calc(100vh - var(--navbar-height));
  overflow-y: auto;
}

.sidebar-section {
  margin-bottom: var(--spacing-lg);
}

.sidebar-section-title {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text-muted);
  margin-bottom: var(--spacing-sm);
  padding-bottom: var(--spacing-sm);
  border-bottom: 1px solid var(--color-border);
}

.sidebar-list {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.sidebar-item {
  padding: var(--spacing-sm) var(--spacing-md);
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-fast);
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
}

.sidebar-item:hover {
  background: var(--color-primary-light);
  color: var(--color-primary);
}

.sidebar-item.active {
  background: var(--color-primary);
  color: white;
}

.sidebar-item .week-badge {
  font-size: var(--font-size-xs);
  color: var(--color-text-muted);
  background: var(--color-bg);
  padding: 1px 6px;
  border-radius: var(--radius-sm);
  margin-left: auto;
}

.sidebar-item.active .week-badge {
  background: rgba(255, 255, 255, 0.2);
  color: white;
}

.dashboard-content {
  padding: var(--spacing-xl);
  max-width: 960px;
  width: 100%;
}

/* ============================================
   Lesson Content
   ============================================ */

.lesson-header {
  margin-bottom: var(--spacing-2xl);
}

.lesson-breadcrumb {
  display: flex;
  gap: var(--spacing-sm);
  align-items: center;
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  margin-bottom: var(--spacing-md);
}

.lesson-breadcrumb a {
  color: var(--color-text-muted);
}

.lesson-breadcrumb a:hover {
  color: var(--color-primary);
}

.lesson-title {
  font-size: var(--font-size-3xl);
  font-weight: var(--font-weight-bold);
  margin-bottom: var(--spacing-sm);
}

.lesson-meta {
  display: flex;
  gap: var(--spacing-lg);
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
}

.lesson-body {
  font-size: var(--font-size-base);
  line-height: var(--line-height-relaxed);
  color: var(--color-text);
}

.lesson-body h2 {
  font-size: var(--font-size-2xl);
  font-weight: var(--font-weight-bold);
  margin-top: var(--spacing-2xl);
  margin-bottom: var(--spacing-md);
  padding-bottom: var(--spacing-sm);
  border-bottom: 1px solid var(--color-border);
}

.lesson-body h3 {
  font-size: var(--font-size-xl);
  font-weight: var(--font-weight-semibold);
  margin-top: var(--spacing-xl);
  margin-bottom: var(--spacing-md);
}

.lesson-body p {
  margin-bottom: var(--spacing-md);
}

.lesson-body ul,
.lesson-body ol {
  margin-bottom: var(--spacing-md);
  padding-left: var(--spacing-xl);
}

.lesson-body ul {
  list-style: disc;
}

.lesson-body ol {
  list-style: decimal;
}

.lesson-body li {
  margin-bottom: var(--spacing-xs);
}

.lesson-body code {
  font-family: var(--font-mono);
  font-size: 0.9em;
  padding: 2px 6px;
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
}

.lesson-body pre {
  background: var(--color-code-bg);
  color: #e2e8f0;
  padding: var(--spacing-lg);
  border-radius: var(--radius-lg);
  overflow-x: auto;
  margin-bottom: var(--spacing-lg);
  font-size: var(--font-size-sm);
  line-height: 1.7;
}

.lesson-body pre code {
  background: none;
  border: none;
  padding: 0;
  color: inherit;
  font-size: inherit;
}

.lesson-body blockquote {
  border-left: 4px solid var(--color-primary);
  padding: var(--spacing-md) var(--spacing-lg);
  margin: var(--spacing-lg) 0;
  background: var(--color-primary-light);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
}

.lesson-body blockquote p {
  margin-bottom: 0;
}

.lesson-body strong {
  font-weight: var(--font-weight-semibold);
}

.lesson-body a {
  color: var(--color-primary);
  text-decoration: underline;
  text-underline-offset: 2px;
}

.lesson-body table {
  width: 100%;
  border-collapse: collapse;
  margin-bottom: var(--spacing-lg);
}

.lesson-body th,
.lesson-body td {
  padding: var(--spacing-sm) var(--spacing-md);
  border: 1px solid var(--color-border);
  text-align: left;
}

.lesson-body th {
  background: var(--color-bg-alt);
  font-weight: var(--font-weight-semibold);
}

.try-it-button {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-sm);
  padding: var(--spacing-sm) var(--spacing-lg);
  background: var(--color-primary);
  color: white;
  border-radius: var(--radius-md);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  transition: all var(--transition-fast);
  margin: var(--spacing-lg) 0;
}

.try-it-button:hover {
  background: var(--color-primary-dark);
}

/* ============================================
   Playground
   ============================================ */

.playground-page {
  padding: var(--spacing-xl) var(--container-padding);
  max-width: var(--container-max);
  margin: 0 auto;
}

.playground-header {
  margin-bottom: var(--spacing-lg);
}

.playground-header h1 {
  font-size: var(--font-size-2xl);
  font-weight: var(--font-weight-bold);
}

.playground-tabs {
  display: flex;
  gap: var(--spacing-sm);
  margin-bottom: var(--spacing-lg);
  border-bottom: 1px solid var(--color-border);
  padding-bottom: 0;
}

.playground-tab {
  padding: var(--spacing-sm) var(--spacing-lg);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--color-text-muted);
  border-bottom: 2px solid transparent;
  transition: all var(--transition-fast);
  margin-bottom: -1px;
}

.playground-tab:hover {
  color: var(--color-text);
}

.playground-tab.active {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
}

.playground-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-lg);
  min-height: 500px;
}

.playground-editor-panel {
  display: flex;
  flex-direction: column;
}

.playground-editor-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--spacing-sm) var(--spacing-md);
  background: var(--color-code-bg);
  color: var(--color-text-muted);
  border-radius: var(--radius-lg) var(--radius-lg) 0 0;
  font-size: var(--font-size-sm);
}

.playground-editor {
  flex: 1;
  background: var(--color-code-bg);
  border: none;
  border-radius: 0 0 var(--radius-lg) var(--radius-lg);
  padding: var(--spacing-lg);
  font-family: var(--font-mono);
  font-size: var(--font-size-sm);
  line-height: 1.7;
  color: #e2e8f0;
  resize: none;
  outline: none;
  tab-size: 2;
}

.playground-editor::placeholder {
  color: #475569;
}

.playground-output-panel {
  display: flex;
  flex-direction: column;
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

.playground-output-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--spacing-sm) var(--spacing-md);
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
}

.playground-output {
  flex: 1;
  padding: var(--spacing-lg);
  font-family: var(--font-mono);
  font-size: var(--font-size-sm);
  line-height: 1.7;
  overflow-y: auto;
  white-space: pre-wrap;
  color: var(--color-text);
}

.btn-run {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-xs);
  padding: var(--spacing-xs) var(--spacing-md);
  background: var(--color-success);
  color: white;
  border-radius: var(--radius-md);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  transition: all var(--transition-fast);
}

.btn-run:hover {
  opacity: 0.9;
}

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

/* ============================================
   Features Section
   ============================================ */

.features-section {
  padding: var(--spacing-4xl) var(--container-padding);
  background: var(--color-bg-alt);
}

.features-grid {
  max-width: var(--container-max);
  margin: 0 auto;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--spacing-xl);
}

.feature-card {
  text-align: center;
  padding: var(--spacing-xl);
}

.feature-icon {
  font-size: 2.5rem;
  margin-bottom: var(--spacing-md);
}

.feature-title {
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-semibold);
  margin-bottom: var(--spacing-sm);
}

.feature-desc {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  line-height: var(--line-height-relaxed);
}

/* ============================================
   Footer
   ============================================ */

.footer {
  background: var(--color-text);
  color: #cbd5e1;
  padding: var(--spacing-3xl) var(--container-padding) var(--spacing-xl);
}

.footer-container {
  max-width: var(--container-max);
  margin: 0 auto;
}

.footer-brand {
  margin-bottom: var(--spacing-2xl);
}

.footer-brand .brand-text {
  font-size: var(--font-size-xl);
  font-weight: var(--font-weight-bold);
}

.footer-tagline {
  font-size: var(--font-size-sm);
  margin-top: var(--spacing-xs);
  color: var(--color-text-muted);
}

.footer-links {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: var(--spacing-2xl);
  margin-bottom: var(--spacing-2xl);
}

.footer-column h4 {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  color: white;
  margin-bottom: var(--spacing-md);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.footer-column ul li {
  margin-bottom: var(--spacing-sm);
}

.footer-column a {
  color: var(--color-text-muted);
  font-size: var(--font-size-sm);
  transition: color var(--transition-fast);
}

.footer-column a:hover {
  color: var(--color-primary);
}

.footer-bottom {
  padding-top: var(--spacing-xl);
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  text-align: center;
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
}

/* ============================================
   Loading & Error States
   ============================================ */

.loading {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--spacing-4xl);
  color: var(--color-text-muted);
}

.spinner {
  width: 2rem;
  height: 2rem;
  border: 3px solid var(--color-border);
  border-top-color: var(--color-primary);
  border-radius: 50%;
  animation: spin 0.6s linear infinite;
  margin-right: var(--spacing-md);
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

.error-state {
  text-align: center;
  padding: var(--spacing-4xl);
  color: var(--color-error);
}

.empty-state {
  text-align: center;
  padding: var(--spacing-4xl);
  color: var(--color-text-muted);
}

/* ============================================
   Mobile Sidebar Overlay
   ============================================ */

.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: var(--color-overlay);
  z-index: 99;
  opacity: 0;
  transition: opacity var(--transition-normal);
}

.sidebar-overlay.open {
  display: block;
  opacity: 1;
}

/* ============================================
   Responsive
   ============================================ */

@media (max-width: 1024px) {
  .dashboard {
    grid-template-columns: 1fr;
  }

  .dashboard-sidebar {
    position: fixed;
    left: -100%;
    top: var(--navbar-height);
    width: var(--sidebar-width);
    height: calc(100vh - var(--navbar-height));
    z-index: 100;
    transition: left var(--transition-normal);
    box-shadow: var(--shadow-xl);
  }

  .dashboard-sidebar.open {
    left: 0;
  }

  .playground-layout {
    grid-template-columns: 1fr;
  }

  .sidebar-toggle-mobile {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    background: var(--color-bg-alt);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    font-size: var(--font-size-sm);
    font-weight: var(--font-weight-medium);
    color: var(--color-text);
    margin-bottom: var(--spacing-lg);
  }
}

@media (max-width: 768px) {
  :root {
    --container-padding: var(--spacing-md);
  }

  .hero-title {
    font-size: var(--font-size-3xl);
  }

  .hero-subtitle {
    font-size: var(--font-size-base);
  }

  .language-cards-grid {
    grid-template-columns: 1fr;
  }

  .footer-links {
    grid-template-columns: 1fr 1fr;
  }

  .features-grid {
    grid-template-columns: 1fr;
  }

  .lesson-title {
    font-size: var(--font-size-2xl);
  }

  .navbar-links {
    position: fixed;
    top: var(--navbar-height);
    left: 0;
    right: 0;
    background: var(--color-bg);
    flex-direction: column;
    padding: var(--spacing-md);
    border-bottom: 1px solid var(--color-border);
    box-shadow: var(--shadow-lg);
    transform: translateY(-100%);
    opacity: 0;
    pointer-events: none;
    transition: all var(--transition-normal);
  }

  .navbar-links.open {
    transform: translateY(0);
    opacity: 1;
    pointer-events: all;
  }

  .navbar-toggle {
    display: flex;
  }
}

@media (max-width: 480px) {
  .hero-title {
    font-size: var(--font-size-2xl);
  }

  .hero-actions {
    flex-direction: column;
  }

  .btn {
    width: 100%;
    justify-content: center;
  }

  .footer-links {
    grid-template-columns: 1fr;
  }

  .playground-editor {
    font-size: var(--font-size-xs);
  }
}

/* ============================================
   Utility Classes
   ============================================ */

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border-width: 0;
}