Add LottieFiles motion-design skill

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0119deVM65AKpJiLTLhEdDg9

.agents/skills/motion-design/reference/property-selection.md

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+# Property Selection
+
+## Position
+
+| Direction | Meaning |
+|-----------|---------|
+| Upward | Growth, improvement, aspiration |
+| Downward | Settling, completion, grounding |
+| Leftward | Regression, backward, departure |
+| Rightward | Progression, forward, arrival |
+| Toward center | Focus, convergence |
+| Away from center | Distribution, expansion |
+
+## Scale
+
+| Direction | Meaning |
+|-----------|---------|
+| Scale up | Importance, activation, proximity |
+| Scale down | Deprioritization, distance |
+| Pulse | Attention, heartbeat, life |
+| Breathing | Presence, waiting |
+
+## Rotation
+
+| Range | Meaning |
+|-------|---------|
+| Small (5-15°) | Subtle adjustment |
+| Medium (45-90°) | Transformation |
+| Full (360°) | Completion, processing |
+| Continuous | Ongoing activity |
+
+## Opacity
+
+| Direction | Meaning |
+|-----------|---------|
+| Fade in | Arrival, enablement |
+| Fade out | Departure, disablement |
+| Partial | Secondary, disabled state |
+
+**Rule**: NEVER opacity alone for important state changes. Combine with position or scale.
+
+## Color
+
+| Transition | Meaning |
+|-----------|---------|
+| To green | Success, go |
+| To red | Error, stop |
+| To blue | Trust, active |
+| To gray | Disabled, inactive |
+| Brightening | Activation, focus |
+| Dimming | Deactivation, background |
+
+## Combined Properties
+
+| Combination | Best For |
+|-------------|----------|
+| Position + Opacity | Content appearing/disappearing |
+| Scale + Opacity | Cards, modals, notifications |
+| Position + Scale | Selected items, focused content |
+| Rotation + Scale | Celebrations, playful activation |
+| Position + Rotation | Organic transitions |
+| Color + Scale | State emphasis |
+
+Primary property carries meaning; secondary adds polish. Two properties is the sweet spot.
+
+## Property Selection by Goal
+
+| Goal | Primary | Secondary | Avoid |
+|------|---------|-----------|-------|
+| Entrance | position | opacity | rotation |
+| Exit | position | opacity | scale up |
+| Button press | scale | color | position |
+| Hover | scale or color | opacity | position |
+| Success | scale | color + opacity | position |
+| Error | position (shake) | color | scale |
+| Loading | rotation | opacity | position |
+| Toggle | position | color | rotation |
+| Notification | position + scale | opacity | rotation |
+| Delete | scale + opacity | position | grow |
+| Selection | scale | color, opacity | rotation |
+| Progress | position or scale | color | opacity |
+
+## Performance
+
+| Property | Performance |
+|----------|-------------|
+| transform (translate, scale, rotate) | Excellent — GPU-accelerated |
+| opacity | Excellent — GPU-accelerated |
+| color / background-color | Good — triggers paint |
+| clip-path | Good — GPU on modern browsers |
+| width / height | Poor — triggers layout |
+| margin / padding | Poor — triggers layout |
+| box-shadow | Poor — expensive paint |
+
+**Rule**: Prefer transform + opacity for all motion.