# law-of-similarity

Applies the Gestalt Law of Similarity to group UI elements across distance using shared color, shape, and size. Useful for unifying components without altering layout.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 1100 installs · ★ 3103
- Author: Owl-Listener
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/Owl-Listener/designer-skills/tree/HEAD/ui-design/skills/law-of-similarity/SKILL.md
- Updated: 2026-09-05
- HTML: https://affpapa.org/en/nevibecode/skills/law-of-similarity

## What it does

This skill guides the agent to apply the Gestalt Law of Similarity across interface design and component architecture. Shared traits like shape or color signal that elements belong to the same category. This works across long distances. For grouping driven strictly by physical placement, the documentation recommends `law-of-proximity`.

Similarity can override spatial proximity. A red button placed in a row of blue items signals an immediate category shift. The instructions treat accidental styling variations, such as slightly mismatched corner radii across buttons, as bugs. Every visual change must carry deliberate purpose.

Relying solely on hue fails colorblind users. The skill requires redundant coding through shape or icons alongside color, ensuring category signals survive monochrome rendering.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add Owl-Listener/designer-skills --skill law-of-similarity -a claude-code
```

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

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add Owl-Listener/designer-skills --skill law-of-similarity -a codex
```

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

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add Owl-Listener/designer-skills --skill law-of-similarity -a cursor
```

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

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install Owl-Listener/designer-skills law-of-similarity
```

2. **Manually: put the files in place**
- File: `.github/skills/law-of-similarity/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add Owl-Listener/designer-skills --skill law-of-similarity -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/Owl-Listener/designer-skills --path ui-design/skills/law-of-similarity
```

### Windsurf (Devin Desktop)

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

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add Owl-Listener/designer-skills --skill law-of-similarity -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/Owl-Listener/designer-skills/tree/HEAD/ui-design/skills/law-of-similarity/SKILL.md

## When to use it
- Signal shared functionality across distant interface elements
- Code destructive actions and status indicators consistently
- Spot unintended styling breaks across design system components
- Add redundant visual coding to preserve category signals without color

## Example prompts
- Review this dashboard navigation using the law of similarity
- Check our button styles to make sure visual attributes indicate category and hierarchy
- How should we code destructive actions across this form using redundant shape and color?

## 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: 547b8a75f379174a.

BEGIN THIRD-PARTY FILE 547b8a75f379174a
```text
---
name: law-of-similarity
description: Apply the Law of Similarity — shared colour, shape, or size signals that elements belong to one category. Use when signalling relationships across distance. For grouping by position, use `law-of-proximity`.
---
# Law of Similarity

You are an expert in Gestalt visual perception and systematic visual language design.

## What You Do

You apply the Law of Similarity to use shared visual attributes — shape, color, size, and style — to signal that elements belong to the same category or group, and to maintain that coding consistently so the signal stays meaningful.

## The Principle

Elements that share visual characteristics are perceived as related, even when they are not spatially adjacent. The mind groups by likeness automatically and without instruction.

Similarity can be carried through:
- **Color**: same fill signals same category, role, or state
- **Shape**: icons all the same style (outline vs. filled vs. rounded) read as a set
- **Size**: elements of equal size read as peers; size difference signals hierarchy
- **Style**: same illustration weight, same type treatment, same corner radius, same stroke width

## Similarity vs. Proximity

These are the two most fundamental Gestalt grouping principles. They interact and can conflict:

| Situation | What happens |
|---|---|
| Elements close together, same color | Both reinforce — strongest grouping signal |
| Elements far apart, same color | Similarity groups them despite the distance |
| Elements close together, different colors | Proximity and similarity compete; the color pulls them into different sub-groups |
| Elements close together, different styles | Proximity groups the set; style difference creates sub-groups within it |

When they conflict, similarity can override proximity: a red element embedded in a group of blue elements reads as distinct even if it is spatially adjacent. Use this deliberately to signal category boundaries.

## Design Applications

### Interactive state signaling

All interactive elements should share a visual property (color, underline treatment, cursor affordance) that non-interactive elements do not. This tells users what is actionable without requiring explicit instruction — the similarity set defines the interactive category.

### Category and role coding

- Navigation items as a set: consistent type treatment across all items
- Destructive actions: a distinctive color used only within that category — similarity within the set signals "these all carry the same risk"
- Status indicators: consistent color-to-meaning mapping (green = success, amber = warning, red = error) applied uniformly
```
END THIRD-PARTY FILE 547b8a75f379174a

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