# medium-300-500ms

A skill that tells your coding agent how to build mid-duration animations: page transitions, modals, staggered reveals.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 484 installs · ★ 124
- Author: dylantarre
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/dylantarre/animation-principles/tree/HEAD/skills/10-by-time-scale/medium-300-500ms/SKILL.md
- Updated: 2025-12-30
- HTML: https://affpapa.org/en/nevibecode/skills/medium-300-500ms

## What it does

This skill covers animations in the 300–500ms range. That window is long enough for a user to notice the motion and short enough that it does not slow the interface down. All twelve animation principles are mapped to this duration, with concrete numbers: 80–120ms of anticipation before the main action, 18–30 frames at 60fps.

The practical half is CSS. Four `cubic-bezier` curves are given for different jobs — smooth natural motion, an expressive entrance, a bouncy feel, dramatic deceleration. There is also a page-transition pattern and an example of staggered list items using `transition-delay`.

Reach for it when the animation has to communicate something: a view change, a feature reveal, a loading state finishing. If your project already has a design system with its own timing tokens, compare the values here against it. Two different motion rhythms in one interface look like a bug.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add dylantarre/animation-principles --skill medium-300-500ms -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/medium-300-500ms/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/medium-300-500ms/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add dylantarre/animation-principles --skill medium-300-500ms -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/medium-300-500ms/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add dylantarre/animation-principles --skill medium-300-500ms -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/medium-300-500ms/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install dylantarre/animation-principles medium-300-500ms
```

2. **Manually: put the files in place**
- File: `.github/skills/medium-300-500ms/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add dylantarre/animation-principles --skill medium-300-500ms -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/dylantarre/animation-principles --path skills/10-by-time-scale/medium-300-500ms
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/medium-300-500ms/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add dylantarre/animation-principles --skill medium-300-500ms -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/dylantarre/animation-principles/tree/HEAD/skills/10-by-time-scale/medium-300-500ms/SKILL.md

## When to use it
- pick a duration and easing curve for a page transition
- stagger the reveal of list items
- animate a multi-step modal sequence
- add bounce to a button or card without making it feel sluggish
- set timings for a chart or diagram animation

## Example prompts
- Build a page transition in the 300–500ms range with easing for smooth natural motion
- Stagger the card reveal in this list with a 50ms delay between items
- Animate the modal opening at 400ms with an expressive entrance

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: f1f6002223969546.

BEGIN THIRD-PARTY FILE f1f6002223969546
````text
---
name: medium-300-500ms
description: Use when building standard animations between 300-500ms - page transitions, significant UI changes, animated illustrations that need clear communication
---

# Medium Animations (300-500ms)

The 300-500ms range is **standard animation territory**. Long enough to be watched, short enough to not impede flow. The workhorse duration for meaningful motion.

## Disney Principles at Medium Duration

### All 12 Principles Applicable

**Squash & Stretch**: Full expression - visible deformation for bouncing, elastic elements. 15-25% stretch feels natural.

**Anticipation**: Clear preparation - 80-120ms anticipation before main action. Pull back before push forward.

**Staging**: Multi-element choreography possible - primary action leads, supporting elements follow.

**Straight Ahead/Pose to Pose**: Pose to pose recommended - define key positions, let easing handle in-betweens.

**Follow Through**: Essential - overlapping action where parts settle at different rates.

**Slow In/Slow Out**: Critical for naturalism - both directions need proper easing.

**Arcs**: Natural motion paths - elements should travel on curves matching real physics.

**Secondary Action**: Multiple secondary actions - hair follows head, shadow follows object.

**Timing**: 18-30 frames at 60fps. Enough frames for nuanced motion.

**Exaggeration**: Full range available - match to brand personality and context.

**Solid Drawing**: Complex transforms work - 3D rotations, perspective shifts.

**Appeal**: Character-defining animations - this is where brand personality lives.

## Easing Recommendations

```css
/* Smooth, natural motion */
transition: all 400ms cubic-bezier(0.4, 0, 0.2, 1);

/* Expressive entrance */
transition: all 450ms cubic-bezier(0.16, 1, 0.3, 1);

/* Bouncy, playful */
transition: transform 400ms cubic-bezier(0.34, 1.56, 0.64, 1);

/* Dramatic deceleration */
transition: all 350ms cubic-bezier(0, 0.55, 0.45, 1);
```

## Best Use Cases

- Page/view transitions
- Complex modal sequences
- Animated illustrations
- Data visualization changes
- Onboarding animations
- Feature reveals
- State machine transitions
- Loading completion celebrations

## Implementation Pattern

```css
.page-enter {
  opacity: 0;
  transform: translateX(30px);
}

.page-enter-active {
  opacity: 1;
  transform: translateX(0);
  transition: opacity 350ms ease-out,
              transform 400ms cubic-bezier(0.16, 1, 0.3, 1);
}

/* Staggered children */
.list-item {
  transition: all 400ms cubic-bezier(0.4, 0, 0.2, 1);
}
.list-item:nth-child(1) { transition-delay: 0ms; }
.list-item:nth-child(2) { transition-delay: 50ms; }
.list-item:nth-child(3) { transition-delay: 100ms; }
```
````
END THIRD-PARTY FILE f1f6002223969546

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