design-system/src/styles.css

/* Be Vietnam Pro — Vietnamese-designed, crisp diacritical rendering */
@import url('https://fonts.googleapis.com/css2?family=Be+Vietnam+Pro:ital,wght@0,100;0,200;0,300;0,400;0,500;0,600;0,700;0,800;0,900;1,100;1,300;1,400;1,500;1,600;1,700&display=swap');
/* JetBrains Mono */
@import url('https://fonts.googleapis.com/css2?family=JetBrains+Mono:wght@100..800&display=swap');

@tailwind base;
@tailwind components;
@tailwind utilities;

/* ── Meridian — Warm Editorial Color Tokens ───────────────────────────────── */
:root {
  color-scheme: light;

  /* Surfaces */
  --background:        #FAFAF8;
  --foreground:        #1C1917;
  --surface:           #F2F0EB;
  --surface-elevated:  #FAFAF8;
  --border:            #D6D3CC;
  --border-subtle:     #E7E5E4;

  /* Text */
  --muted:             #A8A29E;
  --muted-fg:          #78716C;
  --dim:               #57534E;
  --faint:             #44403C;

  /* Text aliases */
  --fg-secondary:      var(--muted-fg);
  --fg-tertiary:       var(--muted);
  --fg-disabled:       #D6D3D1;
  --surface-raised:    var(--surface-elevated);

  /* Brand — forest green */
  --primary:           #166534;
  --primary-fg:        #FFFFFF;
  --primary-subtle:    #F0FDF4;
  --primary-border:    #BBF7D0;

  /* Accent — terracotta */
  --accent:            #C2410C;
  --accent-fg:         #FFFFFF;
  --accent-subtle:     #FFF7ED;
  --accent-border:     #FED7AA;

  /* Status */
  --success:           #16A34A;
  --warning:           #D97706;
  --destructive:       #DC2626;
  --info:              #2563EB;
  --purple:            #7C3AED;
  --highlight:         #F0FDF4;

  /* Choice feedback */
  --choice-chosen-bg:   #FFF7ED;
  --choice-wrong-bg:    #FEF2F2;
  --choice-wrong-border:#FECACA;

  /* Mastery scale (0=unknown → 5=mastered) */
  --mastery-0:         #A8A29E;
  --mastery-0-bg:      #F5F5F4;
  --mastery-1:         #DC2626;
  --mastery-1-bg:      #FEF2F2;
  --mastery-2:         #EA580C;
  --mastery-2-bg:      #FFF7ED;
  --mastery-3:         #D97706;
  --mastery-3-bg:      #FFFBEB;
  --mastery-4:         #16A34A;
  --mastery-4-bg:      #F0FDF4;
  --mastery-5:         #166534;
  --mastery-5-bg:      #DCFCE7;

  /* Shadows */
  --shadow-xs: 0 1px 2px rgba(0,0,0,0.05);
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.10), 0 1px 2px rgba(0,0,0,0.06);
  --shadow-md: 0 4px 6px rgba(0,0,0,0.07), 0 2px 4px rgba(0,0,0,0.06);
  --shadow-lg: 0 10px 15px rgba(0,0,0,0.08), 0 4px 6px rgba(0,0,0,0.05);
  --shadow-xl: 0 20px 25px rgba(0,0,0,0.10), 0 10px 10px rgba(0,0,0,0.04);

  /* Border radius */
  --radius-xs:   4px;
  --radius-sm:   6px;
  --radius-md:   8px;
  --radius-lg:   12px;
  --radius-xl:   16px;
  --radius-full: 9999px;

  /* Easing */
  --z-ease-spring: cubic-bezier(0.34, 1.56, 0.64, 1);
  --z-ease-smooth: cubic-bezier(0.25, 0.46, 0.45, 0.94);
  --z-ease-out:    cubic-bezier(0.0, 0.0, 0.2, 1);

  /* Transitions */
  --transition-fast:  100ms ease;
  --transition-base:  150ms ease;
  --transition-slow:  250ms ease-in-out;

  /* Blur */
  --z-blur-sm: blur(4px);
  --z-blur-md: blur(8px);

  /* Radius aliases */
  --z-radius-sm:  var(--radius-md);
  --z-radius-md:  var(--radius-lg);
  --z-radius-lg:  var(--radius-xl);
  --z-radius-xl:  20px;
}

/* Dark theme */
.dark, [data-theme="dark"] {
  color-scheme: dark;

  --background:        #171410;
  --foreground:        #F5F0E8;
  --surface:           #252219;
  --surface-elevated:  #2D2A22;
  --border:            #3D3A30;
  --border-subtle:     #4F4A40;

  --muted:             #57534E;
  --muted-fg:          #A8A29E;
  --dim:               #78716C;
  --faint:             #57534E;

  --fg-secondary:      var(--muted-fg);
  --fg-tertiary:       var(--muted);
  --fg-disabled:       #44403C;
  --surface-raised:    var(--surface-elevated);

  --primary:           #4ADE80;
  --primary-fg:        #14532D;
  --primary-subtle:    rgba(22, 101, 52, 0.25);
  --primary-border:    #166534;

  --accent:            #FB923C;
  --accent-fg:         #7C2D12;
  --accent-subtle:     rgba(194, 65, 12, 0.20);
  --accent-border:     #C2410C;

  --success:           #4ADE80;
  --warning:           #FCD34D;
  --destructive:       #F87171;
  --info:              #60A5FA;
  --purple:            #A78BFA;
  --highlight:         rgba(22, 101, 52, 0.25);

  --mastery-0:         #78716C;
  --mastery-0-bg:      #292524;
  --mastery-1:         #F87171;
  --mastery-1-bg:      #450A0A;
  --mastery-2:         #FB923C;
  --mastery-2-bg:      #431407;
  --mastery-3:         #FCD34D;
  --mastery-3-bg:      #78350F;
  --mastery-4:         #4ADE80;
  --mastery-4-bg:      #14532D;
  --mastery-5:         #86EFAC;
  --mastery-5-bg:      #052E16;

  --choice-chosen-bg:   rgba(194, 65, 12, 0.15);
  --choice-wrong-bg:    rgba(220, 38, 38, 0.15);
  --choice-wrong-border:rgba(220, 38, 38, 0.35);

  --shadow-xs: 0 1px 2px rgba(0,0,0,0.20);
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.35), 0 1px 2px rgba(0,0,0,0.25);
  --shadow-md: 0 4px 6px rgba(0,0,0,0.30), 0 2px 4px rgba(0,0,0,0.25);
  --shadow-lg: 0 10px 15px rgba(0,0,0,0.35), 0 4px 6px rgba(0,0,0,0.20);
  --shadow-xl: 0 20px 25px rgba(0,0,0,0.40), 0 10px 10px rgba(0,0,0,0.20);
}

/* Accessibility: High contrast */
@media (prefers-contrast: more) {
  :root {
    --muted-fg: #44403C;
    --dim:      #292524;
    --faint:    #1C1917;
    --border:   #A8A29E;
  }
  .dark, [data-theme="dark"] {
    --muted-fg: #D6D3D1;
    --dim:      #E7E5E4;
    --faint:    #F5F5F4;
    --border:   #78716C;
  }
}

/* Accessibility: Reduced transparency */
@media (prefers-reduced-transparency: reduce) {
  :root { --z-blur-sm: none; --z-blur-md: none; }
  [class*="backdrop-blur"] {
    backdrop-filter: none !important;
    background-color: var(--surface) !important;
  }
  .glass-base, .glass-elevated, .glass-brand {
    backdrop-filter: none !important;
    background-color: var(--surface) !important;
    background-image: none !important;
  }
}

/* Accessibility: Windows High Contrast */
@media (forced-colors: active) {
  * { forced-color-adjust: auto; }
  button, .btn, input, select, [role="button"] {
    border: 1px solid ButtonText;
  }
}

/* Accessibility: Touch targets */
@media (pointer: coarse) {
  button, [role="button"], input, select {
    min-height: 44px;
    min-width: 44px;
  }
}

/* Keyboard focus ring */
:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
  border-radius: 3px;
}

body {
  background-color: var(--background);
  color: var(--foreground);
  font-family: 'Be Vietnam Pro', -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
  font-size: 16px;
  line-height: 1.5;
}

/* Surface system */
.glass-base {
  background: var(--surface);
  border: 1px solid var(--border);
  box-shadow: var(--shadow-sm);
}

.glass-elevated {
  background: var(--surface-elevated);
  border: 1px solid var(--border);
  box-shadow: var(--shadow-md);
}

.glass-brand {
  background: var(--primary-subtle);
  border: 1px solid var(--primary-border);
  box-shadow: var(--shadow-sm);
}

.surface-flat    { background: var(--surface); border: 1px solid var(--border); }
.surface-raised  { background: var(--surface-elevated); border: 1px solid var(--border); box-shadow: var(--shadow-sm); }
.surface-overlay { background: var(--background); border: 1px solid var(--border-subtle); box-shadow: var(--shadow-xl); }
.glass-card      { background: var(--surface); border: 1px solid var(--border); box-shadow: var(--shadow-sm); }

/* Button utilities */
.btn-primary, .btn-accent, .btn-outline, .btn-ghost {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  border-radius: var(--radius-md);
  padding: 8px 16px;
  font-family: inherit;
  font-size: 14px;
  font-weight: 500;
  line-height: 20px;
  cursor: pointer;
  transition: background var(--transition-fast), color var(--transition-fast), border-color var(--transition-fast), box-shadow var(--transition-fast);
  border: 1px solid transparent;
}
.btn-primary { background: var(--primary); color: var(--primary-fg); }
.btn-primary:hover { background: #14532D; }
.btn-accent { background: var(--accent); color: var(--accent-fg); }
.btn-accent:hover { background: #9A3412; }
.btn-outline { background: transparent; border-color: var(--border); color: var(--foreground); }
.btn-outline:hover { background: var(--surface); }
.btn-ghost { background: transparent; color: var(--muted-fg); }
.btn-ghost:hover { background: var(--surface); color: var(--foreground); }

/* Text gradients */
.text-gradient-brand {
  background: linear-gradient(135deg, #166534 0%, #15803D 50%, #4ADE80 100%);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

/* Skeleton shimmer */
@keyframes shimmer {
  0%   { background-position: -400px 0; }
  100% { background-position:  400px 0; }
}
.skeleton {
  background: linear-gradient(90deg, #E7E5E4 25%, #D6D3D1 50%, #E7E5E4 75%);
  background-size: 800px 100%;
  animation: shimmer 1.4s infinite linear;
  border-radius: var(--radius-sm);
}
.dark .skeleton, [data-theme="dark"] .skeleton {
  background: linear-gradient(90deg, #3D3A30 25%, #4F4A40 50%, #3D3A30 75%);
  background-size: 800px 100%;
}

/* Answer feedback animations */
@keyframes z-correct-flash {
  0%   { background-color: transparent; }
  40%  { background-color: rgba(22, 163, 74, 0.20); }
  100% { background-color: transparent; }
}
@keyframes z-wrong-shake {
  0%, 100% { transform: translateX(0); }
  15%  { transform: translateX(-5px); }
  35%  { transform: translateX(5px); }
  55%  { transform: translateX(-3px); }
  75%  { transform: translateX(3px); }
}

.z-choice-correct { animation: z-correct-flash 500ms var(--z-ease-out) forwards; }
.z-choice-wrong   { animation: z-wrong-shake 280ms var(--z-ease-out); }

/* Touch ripple */
.ripple-btn { position: relative; overflow: hidden; }
.ripple-btn::after {
  content: '';
  position: absolute;
  width: 200%; height: 200%;
  top: calc(var(--ripple-y, 50%) - 100%);
  left: calc(var(--ripple-x, 50%) - 100%);
  background: rgba(22, 101, 52, 0.12);
  border-radius: 50%;
  transform: scale(0);
  mix-blend-mode: multiply;
  pointer-events: none;
}
.ripple-btn:active::after { transform: scale(1); opacity: 0; transition: transform 0.4s ease, opacity 0.4s ease; }

/* KaTeX */
.katex { font-size: 1em; }

/* Reduced motion */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}