--transition-duration-fast: 0.1s;
--transition-duration-standard: 0.2s;
--transition-duration-slow: 0.3s;

/* ❌ Avoid */
transition: all 0.3s ease;

/* ✅ Prefer */
transition: transform 0.3s ease;

--duration-instant: 0.1s;
--duration-fast: 0.2s;
--duration-normal: 0.3s;
--duration-slow: 0.5s;
--duration-slower: 0.8s;

--ease-standard: ease-in-out;
--ease-smooth: cubic-bezier(0.4, 0, 0.2, 1);
--ease-bounce: cubic-bezier(0.175, 0.885, 0.32, 1.275);

.card {
  transition: transform var(--duration-fast) var(--ease-smooth);
}

.card:hover {
  transform: translateY(-4px);
}

.input:focus {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

/* ❌ Triggers layout */
.box {
  position: relative;
  transition: left 0.3s;
}
.box:hover {
  left: 10px;
}

/* ✅ GPU accelerated */
.box {
  transition: transform 0.3s;
}
.box:hover {
  transform: translateX(10px);
}

.heavy-animation {
  will-change: transform, opacity;
}

.transition-transform {
  transition-property: transform;
  transition-duration: var(--duration-normal);
  transition-timing-function: var(--ease-smooth);
}

.transition-colors {
  transition-property: color, background-color, border-color;
  transition-duration: var(--duration-fast);
}

<button class="transition-colors hover:bg-primary">
  Click me
</button>

[data-state="loading"] {
  opacity: 0.5;
  cursor: wait;
}

[data-state="success"] {
  background: var(--color-success);
}

[data-state="error"] {
  background: var(--color-error);
  animation: shake 0.3s;
}

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

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

.animate-fadeIn {
  animation: fadeIn var(--duration-normal) var(--ease-smooth);
}

.animate-slideUp {
  animation: slideUp var(--duration-normal) var(--ease-smooth);
}

.animate-pulse {
  animation: pulse 2s infinite;
}

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

.list-item {
  opacity: 0;
  animation: fadeIn 0.3s forwards;
}

.list-item:nth-child(1) { animation-delay: 0.1s; }
.list-item:nth-child(2) { animation-delay: 0.2s; }
.list-item:nth-child(3) { animation-delay: 0.3s; }

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  transition: gap 0.3s ease;
}

.grid:hover {
  gap: 2rem;
}

@container (min-width: 400px) {
  .card {
    animation: expandCard 0.3s ease;
  }
}

::view-transition-old(root) {
  animation: fade-out 0.3s;
}

::view-transition-new(root) {
  animation: fade-in 0.3s;
}

:root {
  /* Durations */
  --d-1: 0.1s;
  --d-2: 0.2s;
  --d-3: 0.3s;
  --d-4: 0.5s;
  
  /* Easings */
  --ease-1: ease;
  --ease-2: ease-in-out;
  --ease-3: var(--ease-smooth);
}

.btn {
  /* Base styles */
  padding: 0.5rem 1rem;
  border-radius: 0.25rem;
  
  /* Transition setup */
  transition-property: transform, background-color, box-shadow;
  transition-duration: var(--d-2);
  transition-timing-function: var(--ease-2);
}

.btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

.btn:active {
  transform: translateY(0);
  transition-duration: var(--d-1);
}

/* ❌ Performance killer */
transition: all 0.3s;

/* ❌ Causes reflow */
transition: width 0.3s;

/* ✅ Prepare browser */
will-change: transform;

.card {
  --lift: 0;
  --shadow: 0 2px 4px rgba(0,0,0,0.1);
  
  transform: translateY(var(--lift));
  box-shadow: var(--shadow);
  transition: transform 0.2s, box-shadow 0.2s;
}

.card:hover {
  --lift: -4px;
  --shadow: 0 8px 16px rgba(0,0,0,0.15);
}

:root {
  /* Motion tokens */
  --motion-fade-in: fadeIn var(--d-3) var(--ease-2);
  --motion-slide-up: slideUp var(--d-3) var(--ease-3);
  --motion-scale: scale var(--d-2) var(--ease-1);
  
  /* Interaction tokens */
  --interact-hover: transform var(--d-2) var(--ease-2);
  --interact-press: transform var(--d-1) var(--ease-1);
}