/* =========================================================
   IT English Trainer — Global Styles
   Design system: GitHub + VS Code aesthetic, Light theme
   ========================================================= */

/* --- CSS Custom Properties --- */
:root {
  /* Surfaces — soft, airy, light */
  --color-bg:          #f4f6fc;
  --color-surface:     #ffffff;
  --color-surface-alt: #f1f3fb;
  --color-border:      #e2e6f2;
  --color-border-soft: #edf0f8;

  /* Brand — vibrant indigo / violet */
  --color-primary:       #5b5bf5;
  --color-primary-hover: #4747e0;
  --color-primary-light: #e8e8ff;
  --color-primary-soft:  #f0f0ff;

  --color-success:     #12a150;
  --color-success-bg:  #d9fbe7;
  --color-warning:     #b67400;
  --color-warning-bg:  #fff4d6;
  --color-danger:      #e5484d;
  --color-danger-bg:   #ffe9e9;
  --color-purple:      #8b5cf6;
  --color-purple-bg:   #f3ecff;
  --color-orange:      #f5871f;
  --color-orange-bg:   #fff0df;

  /* Gradients for a livelier look */
  --gradient-brand:   linear-gradient(135deg, #6366f1 0%, #8b5cf6 50%, #ec4899 100%);
  --gradient-brand-2: linear-gradient(135deg, #5b5bf5 0%, #7c3aed 100%);
  --gradient-soft:    linear-gradient(135deg, #eef0ff 0%, #f7eefe 100%);
  --gradient-success: linear-gradient(135deg, #12a150 0%, #14b8a6 100%);

  /* Text */
  --color-text:        #1c1e2e;
  --color-text-muted:  #5a6072;
  --color-text-light:  #969cb0;
  --color-text-inv:    #ffffff;

  /* Code */
  --color-code-bg:     #f5f6fc;
  --color-code-border: #e2e6f2;
  --color-code-text:   #2b2d42;

  /* Levels */
  --color-beginner:    #12a150;
  --color-intermediate:#b67400;
  --color-advanced:    #e5484d;

  /* Spacing */
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-8: 32px;
  --space-10: 40px;
  --space-12: 48px;
  --space-16: 64px;

  /* Border radius — softer, rounder */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --radius-xl: 20px;
  --radius-full: 9999px;

  /* Shadows — soft indigo-tinted */
  --shadow-sm:  0 1px 3px rgba(40,42,80,0.06), 0 1px 2px rgba(40,42,80,0.05);
  --shadow-md:  0 6px 16px rgba(60,60,120,0.09), 0 2px 6px rgba(60,60,120,0.06);
  --shadow-lg:  0 14px 32px rgba(60,60,120,0.13), 0 6px 14px rgba(60,60,120,0.08);
  --shadow-card: 0 2px 8px rgba(60,60,120,0.06);

  /* Typography */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Noto Sans', Helvetica, Arial, sans-serif;
  --font-mono: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, Courier, monospace;

  /* Font sizes */
  --text-xs:   11px;
  --text-sm:   12px;
  --text-base: 14px;
  --text-md:   16px;
  --text-lg:   18px;
  --text-xl:   20px;
  --text-2xl:  24px;
  --text-3xl:  32px;

  /* Transitions */
  --transition-fast:  0.15s ease;
  --transition-base:  0.25s ease;
  --transition-slow:  0.4s ease;

  /* Layout */
  --navbar-height: 60px;
  --sidebar-width: 260px;
}

/* --- 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(--text-base);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.6;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* --- Typography --- */
h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  line-height: 1.3;
  color: var(--color-text);
}

h1 { font-size: var(--text-3xl); }
h2 { font-size: var(--text-2xl); }
h3 { font-size: var(--text-xl); }
h4 { font-size: var(--text-lg); }
h5 { font-size: var(--text-md); }

p {
  line-height: 1.7;
  color: var(--color-text);
}

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

code {
  font-family: var(--font-mono);
  font-size: 0.875em;
  background: var(--color-code-bg);
  border: 1px solid var(--color-code-border);
  border-radius: var(--radius-sm);
  padding: 2px 6px;
  color: var(--color-code-text);
}

pre {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  background: var(--color-code-bg);
  border: 1px solid var(--color-code-border);
  border-radius: var(--radius-md);
  padding: var(--space-4);
  overflow-x: auto;
  line-height: 1.7;
  color: var(--color-code-text);
  position: relative;
}

pre code {
  background: none;
  border: none;
  padding: 0;
  font-size: inherit;
}

/* --- Buttons --- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-4);
  font-family: var(--font-sans);
  font-size: var(--text-sm);
  font-weight: 500;
  line-height: 1.5;
  border-radius: var(--radius-md);
  border: 1px solid transparent;
  cursor: pointer;
  transition: all var(--transition-fast);
  text-decoration: none;
  white-space: nowrap;
  user-select: none;
}

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

.btn-primary {
  background: var(--gradient-brand-2);
  color: var(--color-text-inv);
  border-color: transparent;
  box-shadow: 0 4px 12px rgba(91,91,245,0.28);
}
.btn-primary:hover:not(:disabled) {
  filter: brightness(1.06);
  transform: translateY(-1px);
  color: var(--color-text-inv);
  text-decoration: none;
  box-shadow: 0 6px 18px rgba(91,91,245,0.36);
}
.btn-primary:active:not(:disabled) { transform: translateY(0); }

.btn-secondary {
  background: var(--color-surface);
  color: var(--color-text);
  border-color: var(--color-border);
}
.btn-secondary:hover:not(:disabled) {
  background: var(--color-surface-alt);
  border-color: #a8b0bb;
  color: var(--color-text);
  text-decoration: none;
}

.btn-success {
  background: var(--color-success);
  color: white;
  border-color: var(--color-success);
}
.btn-success:hover:not(:disabled) {
  background: #147d32;
  text-decoration: none;
  color: white;
}

.btn-danger {
  background: var(--color-danger);
  color: white;
  border-color: var(--color-danger);
}
.btn-danger:hover:not(:disabled) {
  background: #a40e26;
  text-decoration: none;
  color: white;
}

.btn-outline {
  background: transparent;
  color: var(--color-primary);
  border-color: var(--color-primary);
}
.btn-outline:hover:not(:disabled) {
  background: var(--color-primary-soft);
  text-decoration: none;
}

.btn-ghost {
  background: transparent;
  color: var(--color-text-muted);
  border-color: transparent;
}
.btn-ghost:hover:not(:disabled) {
  background: var(--color-surface-alt);
  color: var(--color-text);
  text-decoration: none;
}

.btn-sm {
  padding: 4px 10px;
  font-size: var(--text-xs);
}

.btn-lg {
  padding: var(--space-3) var(--space-6);
  font-size: var(--text-md);
}

.btn-icon {
  padding: var(--space-2);
  border-radius: var(--radius-md);
}

/* --- Form Elements --- */
.form-group {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  margin-bottom: var(--space-4);
}

.form-label {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-text);
}

.form-input,
.form-select,
.form-textarea {
  width: 100%;
  padding: var(--space-2) var(--space-3);
  font-family: var(--font-sans);
  font-size: var(--text-base);
  color: var(--color-text);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  outline: none;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
  line-height: 1.5;
}

.form-input:focus,
.form-select:focus,
.form-textarea:focus {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(9,105,218,0.12);
}

.form-input::placeholder,
.form-textarea::placeholder {
  color: var(--color-text-light);
}

.form-textarea {
  resize: vertical;
  min-height: 100px;
}

.form-hint {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
}

.form-error {
  font-size: var(--text-xs);
  color: var(--color-danger);
}

/* --- Cards --- */
.card {
  background: var(--color-surface);
  border: 1px solid var(--color-border-soft);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-card);
  overflow: hidden;
  transition: box-shadow var(--transition-base), transform var(--transition-base);
}

.card-header {
  padding: var(--space-4) var(--space-6);
  border-bottom: 1px solid var(--color-border-soft);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
}

.card-body {
  padding: var(--space-6);
}

.card-footer {
  padding: var(--space-4) var(--space-6);
  border-top: 1px solid var(--color-border-soft);
  background: var(--color-bg);
}

/* --- Badges --- */
.badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 2px var(--space-2);
  font-size: var(--text-xs);
  font-weight: 600;
  border-radius: var(--radius-full);
  border: 1px solid transparent;
  white-space: nowrap;
}

.badge-primary { background: var(--color-primary-light); color: var(--color-primary); border-color: #c9c9ff; }
.badge-success { background: var(--color-success-bg); color: var(--color-success); border-color: #a6efc6; }
.badge-warning { background: var(--color-warning-bg); color: var(--color-warning); border-color: #f0d68a; }
.badge-danger  { background: var(--color-danger-bg);  color: var(--color-danger);  border-color: #ffc4c4; }
.badge-purple  { background: var(--color-purple-bg);  color: var(--color-purple);  border-color: #ddccff; }
.badge-orange  { background: var(--color-orange-bg);  color: var(--color-orange);  border-color: #fdd8ae; }
.badge-gray    { background: var(--color-surface-alt); color: var(--color-text-muted); border-color: var(--color-border); }

.badge-beginner     { background: var(--color-success-bg); color: var(--color-success); border-color: #a6efc6; }
.badge-intermediate { background: var(--color-warning-bg); color: var(--color-warning); border-color: #f0d68a; }
.badge-advanced     { background: var(--color-danger-bg); color: var(--color-danger); border-color: #ffc4c4; }

/* --- Progress Bar --- */
.progress-bar-wrap {
  background: var(--color-border-soft);
  border-radius: var(--radius-full);
  overflow: hidden;
  height: 8px;
}

.progress-bar-fill {
  height: 100%;
  border-radius: var(--radius-full);
  background: var(--gradient-brand);
  transition: width 0.5s ease;
}

.progress-bar-fill.success { background: var(--color-success); }
.progress-bar-fill.warning { background: var(--color-warning); }

/* --- Navbar --- */
.navbar {
  height: var(--navbar-height);
  background: rgba(255,255,255,0.85);
  backdrop-filter: saturate(180%) blur(12px);
  -webkit-backdrop-filter: saturate(180%) blur(12px);
  border-bottom: 1px solid var(--color-border-soft);
  display: flex;
  align-items: center;
  padding: 0 var(--space-6);
  gap: var(--space-4);
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: 0 2px 12px rgba(60,60,120,0.05);
}

.navbar-brand {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  text-decoration: none;
  font-weight: 700;
  font-size: var(--text-md);
  color: var(--color-text);
}

.navbar-brand:hover { text-decoration: none; color: var(--color-text); }

.navbar-brand .brand-icon {
  width: 32px;
  height: 32px;
  background: linear-gradient(135deg, var(--color-primary), var(--color-purple));
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: var(--text-md);
  font-weight: 700;
}

.navbar-nav {
  display: flex;
  align-items: center;
  gap: var(--space-1);
  list-style: none;
  flex: 1;
}

.navbar-nav a {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-md);
  color: var(--color-text-muted);
  font-size: var(--text-sm);
  font-weight: 500;
  text-decoration: none;
  transition: all var(--transition-fast);
}

.navbar-nav a:hover,
.navbar-nav a.active {
  background: var(--color-surface-alt);
  color: var(--color-text);
  text-decoration: none;
}

.navbar-nav a.active {
  color: var(--color-primary);
  font-weight: 600;
}

.navbar-actions {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  margin-left: auto;
}

.user-avatar {
  width: 32px;
  height: 32px;
  border-radius: var(--radius-full);
  background: linear-gradient(135deg, var(--color-primary), var(--color-purple));
  color: white;
  font-weight: 700;
  font-size: var(--text-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  flex-shrink: 0;
}

/* --- Alerts --- */
.alert {
  display: flex;
  align-items: flex-start;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-4);
  border-radius: var(--radius-md);
  border: 1px solid;
  font-size: var(--text-sm);
}

.alert-info    { background: var(--color-primary-light); border-color: #b6d4f7; color: #0550ae; }
.alert-success { background: var(--color-success-bg); border-color: #aeefc4; color: #1a7f37; }
.alert-warning { background: var(--color-warning-bg); border-color: #e8c84e; color: #9a6700; }
.alert-danger  { background: var(--color-danger-bg); border-color: #ffc1c5; color: #cf222e; }

.alert-icon { flex-shrink: 0; font-size: var(--text-md); }

/* --- Tabs --- */
.tabs {
  display: flex;
  gap: 0;
  border-bottom: 1px solid var(--color-border);
  overflow-x: auto;
}

.tab-btn {
  padding: var(--space-3) var(--space-4);
  background: none;
  border: none;
  border-bottom: 2px solid transparent;
  color: var(--color-text-muted);
  font-family: var(--font-sans);
  font-size: var(--text-sm);
  font-weight: 500;
  cursor: pointer;
  white-space: nowrap;
  transition: all var(--transition-fast);
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.tab-btn:hover {
  color: var(--color-text);
  border-bottom-color: var(--color-border);
}

.tab-btn.active {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
  font-weight: 600;
}

.tab-content { display: none; }
.tab-content.active { display: block; }

/* --- Terminal Block --- */
.terminal {
  background: #1e2128;
  border-radius: var(--radius-lg);
  overflow: hidden;
  font-family: var(--font-mono);
  box-shadow: var(--shadow-md);
}

.terminal-header {
  background: #2c313a;
  padding: var(--space-3) var(--space-4);
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.terminal-dots {
  display: flex;
  gap: 6px;
}

.terminal-dot {
  width: 12px;
  height: 12px;
  border-radius: var(--radius-full);
}

.terminal-dot.red    { background: #ff5f57; }
.terminal-dot.yellow { background: #febc2e; }
.terminal-dot.green  { background: #28c840; }

.terminal-title {
  color: #636d83;
  font-size: var(--text-xs);
  margin: 0 auto;
}

.terminal-body {
  padding: var(--space-4);
  color: #abb2bf;
  font-size: var(--text-sm);
  line-height: 1.8;
  min-height: 80px;
}

.terminal-prompt {
  color: #61afef;
}

.terminal-command {
  color: #98c379;
}

.terminal-output {
  color: #abb2bf;
}

.terminal-error {
  color: #e06c75;
}

/* --- Documentation Viewer --- */
.doc-viewer {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

.doc-viewer-header {
  background: var(--color-surface-alt);
  border-bottom: 1px solid var(--color-border);
  padding: var(--space-3) var(--space-4);
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.doc-source-badge {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 4px var(--space-3);
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  text-decoration: none;
}

.doc-source-badge:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
  text-decoration: none;
}

.doc-viewer-body {
  padding: var(--space-5);
  font-size: var(--text-base);
  line-height: 1.7;
}

.doc-viewer-body h1,
.doc-viewer-body h2,
.doc-viewer-body h3 {
  margin: var(--space-5) 0 var(--space-3);
  padding-bottom: var(--space-2);
  border-bottom: 1px solid var(--color-border-soft);
}

.doc-viewer-body h1:first-child,
.doc-viewer-body h2:first-child,
.doc-viewer-body h3:first-child {
  margin-top: 0;
}

.doc-viewer-body p { margin-bottom: var(--space-3); }
.doc-viewer-body ul, .doc-viewer-body ol {
  margin: var(--space-3) 0;
  padding-left: var(--space-6);
}
.doc-viewer-body li { margin-bottom: var(--space-1); }

.doc-viewer-body .note,
.doc-viewer-body .warning,
.doc-viewer-body .tip {
  padding: var(--space-3) var(--space-4);
  border-radius: var(--radius-md);
  border-left: 4px solid;
  margin: var(--space-4) 0;
  font-size: var(--text-sm);
}

.doc-viewer-body .note    { background: var(--color-primary-light); border-color: var(--color-primary); }
.doc-viewer-body .warning { background: var(--color-warning-bg); border-color: var(--color-warning); }
.doc-viewer-body .tip     { background: var(--color-success-bg); border-color: var(--color-success); }

/* Vocabulary tooltip */
.vocab-word {
  cursor: pointer;
  border-bottom: 2px dotted var(--color-primary);
  color: inherit;
  transition: background var(--transition-fast);
  padding: 0 1px;
}
.vocab-word:hover {
  background: var(--color-primary-light);
  border-radius: 2px;
}

/* --- Tooltip / Vocab Popup --- */
.vocab-tooltip {
  position: fixed;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
  padding: var(--space-4);
  width: 280px;
  z-index: 1000;
  display: none;
  animation: fadeInUp 0.15s ease;
}

.vocab-tooltip.visible { display: block; }

.vocab-tooltip-word {
  font-size: var(--text-md);
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 4px;
}

.vocab-tooltip-phonetic {
  font-size: var(--text-xs);
  color: var(--color-text-light);
  font-family: var(--font-mono);
  margin-bottom: var(--space-2);
}

.vocab-tooltip-def {
  font-size: var(--text-sm);
  color: var(--color-text);
  margin-bottom: var(--space-2);
  line-height: 1.5;
}

.vocab-tooltip-ru {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  background: var(--color-surface-alt);
  padding: 4px var(--space-2);
  border-radius: var(--radius-sm);
  margin-bottom: var(--space-3);
}

.vocab-tooltip-example {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  font-style: italic;
  border-left: 3px solid var(--color-border);
  padding-left: var(--space-2);
  margin-bottom: var(--space-3);
}

/* --- Stats Cards --- */
.stat-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-5);
  text-align: center;
  transition: box-shadow var(--transition-fast), transform var(--transition-fast);
}

.stat-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-1px);
}

.stat-value {
  font-size: var(--text-3xl);
  font-weight: 700;
  color: var(--color-primary);
  line-height: 1;
  margin-bottom: var(--space-1);
}

.stat-label {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
}

/* --- Loading States --- */
.loading-spinner {
  width: 20px;
  height: 20px;
  border: 2px solid var(--color-border);
  border-top-color: var(--color-primary);
  border-radius: 50%;
  animation: spin 0.7s linear infinite;
  display: inline-block;
}

.loading-dots::after {
  content: '';
  animation: dots 1.5s steps(4, end) infinite;
}

/* --- Utility Classes --- */
.container {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 var(--space-6);
}

.flex { display: flex; }
.flex-col { display: flex; flex-direction: column; }
.items-center { align-items: center; }
.items-start { align-items: flex-start; }
.justify-between { justify-content: space-between; }
.justify-center { justify-content: center; }
.gap-2 { gap: var(--space-2); }
.gap-3 { gap: var(--space-3); }
.gap-4 { gap: var(--space-4); }
.gap-6 { gap: var(--space-6); }
.gap-8 { gap: var(--space-8); }
.flex-1 { flex: 1; }
.flex-wrap { flex-wrap: wrap; }

.grid-2 { display: grid; grid-template-columns: 1fr 1fr; gap: var(--space-4); }
.grid-3 { display: grid; grid-template-columns: 1fr 1fr 1fr; gap: var(--space-4); }
.grid-4 { display: grid; grid-template-columns: repeat(4,1fr); gap: var(--space-4); }

.text-sm    { font-size: var(--text-sm); }
.text-xs    { font-size: var(--text-xs); }
.text-muted { color: var(--color-text-muted); }
.text-light { color: var(--color-text-light); }
.text-primary { color: var(--color-primary); }
.text-success { color: var(--color-success); }
.text-warning { color: var(--color-warning); }
.text-danger  { color: var(--color-danger); }
.font-mono  { font-family: var(--font-mono); }
.font-bold  { font-weight: 700; }
.font-semi  { font-weight: 600; }

.mt-2 { margin-top: var(--space-2); }
.mt-3 { margin-top: var(--space-3); }
.mt-4 { margin-top: var(--space-4); }
.mt-6 { margin-top: var(--space-6); }
.mb-2 { margin-bottom: var(--space-2); }
.mb-3 { margin-bottom: var(--space-3); }
.mb-4 { margin-bottom: var(--space-4); }
.mb-6 { margin-bottom: var(--space-6); }

.p-4 { padding: var(--space-4); }
.p-6 { padding: var(--space-6); }
.py-4 { padding-top: var(--space-4); padding-bottom: var(--space-4); }
.px-4 { padding-left: var(--space-4); padding-right: var(--space-4); }

.rounded-sm { border-radius: var(--radius-sm); }
.rounded-md { border-radius: var(--radius-md); }
.rounded-lg { border-radius: var(--radius-lg); }
.rounded-full { border-radius: var(--radius-full); }

.hidden { display: none !important; }
.w-full { width: 100%; }
.truncate { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }

/* --- Animations --- */
@keyframes spin {
  to { transform: rotate(360deg); }
}

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

@keyframes fadeIn {
  from { opacity: 0; }
  to   { opacity: 1; }
}

@keyframes slideInRight {
  from { opacity: 0; transform: translateX(20px); }
  to   { opacity: 1; transform: translateX(0); }
}

@keyframes pulse {
  0%, 100% { transform: scale(1); }
  50%       { transform: scale(1.05); }
}

@keyframes dots {
  0%  { content: ''; }
  25% { content: '.'; }
  50% { content: '..'; }
  75% { content: '...'; }
}

@keyframes shimmer {
  from { background-position: -200% 0; }
  to   { background-position: 200% 0; }
}

/* Skeleton loader */
.skeleton {
  background: linear-gradient(90deg, var(--color-surface-alt) 25%, var(--color-border-soft) 50%, var(--color-surface-alt) 75%);
  background-size: 200% 100%;
  animation: shimmer 1.4s infinite;
  border-radius: var(--radius-md);
}

/* --- Scrollbar styling --- */
::-webkit-scrollbar { width: 8px; height: 8px; }
::-webkit-scrollbar-track { background: var(--color-bg); }
::-webkit-scrollbar-thumb {
  background: var(--color-border);
  border-radius: var(--radius-full);
  border: 2px solid var(--color-bg);
}
::-webkit-scrollbar-thumb:hover { background: #a8b0bb; }

/* --- Toast Notifications --- */
.toast-container {
  position: fixed;
  bottom: var(--space-6);
  right: var(--space-6);
  z-index: 2000;
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.toast {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-3) var(--space-4);
  box-shadow: var(--shadow-lg);
  display: flex;
  align-items: center;
  gap: var(--space-3);
  min-width: 280px;
  max-width: 380px;
  animation: slideInRight 0.25s ease;
  font-size: var(--text-sm);
}

.toast.success { border-left: 3px solid var(--color-success); }
.toast.error   { border-left: 3px solid var(--color-danger); }
.toast.info    { border-left: 3px solid var(--color-primary); }

/* --- Modal --- */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.4);
  z-index: 500;
  display: flex;
  align-items: center;
  justify-content: center;
  animation: fadeIn 0.2s ease;
  padding: var(--space-4);
}

.modal-overlay.hidden { display: none; }

.modal {
  background: var(--color-surface);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-lg);
  width: 100%;
  max-width: 540px;
  max-height: 90vh;
  overflow-y: auto;
  animation: fadeInUp 0.25s ease;
}

.modal-header {
  padding: var(--space-5) var(--space-6);
  border-bottom: 1px solid var(--color-border);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.modal-body { padding: var(--space-5) var(--space-6); }

.modal-footer {
  padding: var(--space-4) var(--space-6);
  border-top: 1px solid var(--color-border);
  display: flex;
  gap: var(--space-2);
  justify-content: flex-end;
}

/* --- Responsive --- */
@media (max-width: 768px) {
  :root { --navbar-height: 56px; }
  .grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr; }
  .navbar-nav { display: none; }
  .container { padding: 0 var(--space-4); }
  .navbar { padding: 0 var(--space-4); gap: var(--space-2); }
  .navbar-brand { font-size: var(--text-sm); }
  .navbar-brand .brand-icon { width: 28px; height: 28px; font-size: var(--text-sm); }
  /* Trim long user name in the navbar on small screens */
  #nav-user-name, #teacher-name { display: none; }
  .modal { max-width: 100%; border-radius: var(--radius-lg); }
  .modal-header, .modal-body, .modal-footer { padding-left: var(--space-4); padding-right: var(--space-4); }
  h1 { font-size: var(--text-2xl); }
  h2 { font-size: var(--text-xl); }
  /* Tables scroll horizontally instead of overflowing */
  .student-table, .vocab-table { display: block; overflow-x: auto; white-space: nowrap; }
}

@media (max-width: 480px) {
  .btn { padding: var(--space-2) var(--space-3); }
  .navbar-actions { gap: var(--space-2); }
}

/* Cloud auto-sync status pill in the navbar */
.cloud-status {
  font-size: 12px;
  font-weight: 600;
  padding: 4px 10px;
  border-radius: var(--radius-full);
  background: var(--color-surface-alt);
  white-space: nowrap;
}
@media (max-width: 560px) { .cloud-status { display: none; } }