# physics-intuition

An animation skill that makes agent-generated motion feel weighted: falls, jumps, collisions and inertia.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 569 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/02-by-thinking-style/physics-intuition/SKILL.md
- Updated: 2025-12-30
- HTML: https://affpapa.org/en/nevibecode/skills/physics-intuition

## What it does

The skill hands the agent a physicist's mental model: every object has mass, every motion has cause and consequence. Before animating, the agent asks what the thing weighs and builds the motion from that answer. A feather and a bowling ball both fall, but they tell different stories, and the viewer should feel the difference without analysing it.

Inside is a walkthrough of the twelve animation principles read through physics: squash & stretch, timing, slow in & slow out, arcs, secondary action, follow through and overlapping action, anticipation, exaggeration, staging, straight ahead and pose to pose, solid drawing, appeal. There is also a practical section on what to change when motion reads as floaty or stiff. Floaty: more ease-in at the start, stronger ease-out at stops, settling oscillations, secondary elements that lag. Stiff: squash at impact points, stretch during fast movement, arcs in every trajectory, body parts arriving at different times.

The rule the skill keeps returning to: audiences don't analyse physics, they feel it. Accuracy is not the goal, believability is. Sometimes breaking physics on purpose, like hanging in mid-air before a fall, lands harder than obeying it. Worth remembering when you are fixing generated animation and can't say why it fails to convince.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add dylantarre/animation-principles --skill physics-intuition -a claude-code
```

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

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add dylantarre/animation-principles --skill physics-intuition -a codex
```

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

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add dylantarre/animation-principles --skill physics-intuition -a cursor
```

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

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install dylantarre/animation-principles physics-intuition
```

2. **Manually: put the files in place**
- File: `.github/skills/physics-intuition/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add dylantarre/animation-principles --skill physics-intuition -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/dylantarre/animation-principles --path skills/02-by-thinking-style/physics-intuition
```

### Windsurf (Devin Desktop)

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

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add dylantarre/animation-principles --skill physics-intuition -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/02-by-thinking-style/physics-intuition/SKILL.md

## When to use it
- make a falling object read as genuinely heavy
- remove floatiness from a character's motion
- add lag to hair and clothing behind the body
- break an impact into squash and stretch
- replace a straight-line path with an arc

## Example prompts
- the character jumps and lands — make the landing heavy with squash at the impact point
- the ball animation looks weightless, add ease-in at the start and settling oscillations at the stop
- the arm moves in a straight line and looks robotic, put it on a pendulum arc from the shoulder

## 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: ee2aa89d95008797.

BEGIN THIRD-PARTY FILE ee2aa89d95008797
```text
---
name: physics-intuition
description: Use when motion needs to feel physically grounded—objects falling, characters jumping, things colliding, or any element that should obey believable weight and momentum.
---

# Physics Intuition

Think like a physicist watching the world move. Every object has mass. Every motion has cause and consequence.

## Core Mental Model

Before animating anything, ask: **What does this weigh?**

A feather and a bowling ball both fall, but they tell completely different stories. Your job is to make the audience *feel* that weight without thinking about it.

## The 12 Principles Through Physics

**Squash & Stretch** — Mass is conserved. When something compresses, it must bulge. A bouncing ball flattens on impact because its volume has to go somewhere.

**Timing** — Heavy = slow to start, slow to stop. Light = quick reactions. A truck and a bicycle brake very differently.

**Slow In & Slow Out** — Nothing starts or stops instantly. Acceleration and deceleration are the fingerprints of mass.

**Arcs** — Gravity curves everything. Even a punch follows a pendulum path from the shoulder. Straight lines feel robotic.

**Secondary Action** — When the main mass moves, attached masses follow with delay. Hair, clothing, jowls—they're all passengers on the physics train.

**Follow Through & Overlapping Action** — Different masses have different momentum. A character stops, but their belly keeps going. This is inertia made visible.

**Anticipation** — Force requires windup. You can't push without first pulling back. Show the gathering of energy before release.

**Exaggeration** — Push physics past reality to *feel* more real. A heavy landing needs more squash than actual physics would produce.

**Staging** — Position elements so physical relationships read clearly. The audience must understand spatial cause and effect.

**Straight Ahead & Pose to Pose** — Use straight ahead for chaotic physics (explosions, water). Use pose to pose for controlled physics (a character lifting something).

**Solid Drawing** — Volume must remain consistent. A character can't lose mass between frames without the audience noticing something is wrong.
```
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First 2208 of 3020 bytes. © dylantarre · MIT · https://github.com/dylantarre/animation-principles/tree/HEAD/skills/02-by-thinking-style/physics-intuition/SKILL.md

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