# law-of-common-region

A Gestalt skill that tells your agent when to group elements with a container, background or border instead of spacing alone.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 1700 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-common-region/SKILL.md
- Updated: 2026-09-05
- HTML: https://affpapa.org/en/nevibecode/skills/law-of-common-region

## What it does

The skill teaches an agent to apply the Law of Common Region: elements inside one boundary or on a shared background read as a group even when they sit far apart. It covers the principle itself, a side-by-side comparison with the Law of Proximity, and a table of typical uses — cards, sidebars, modals, form sections, table rows, tag groups, tooltips.

The rule of thumb it gives: try proximity first, reach for a container when spacing is not enough. Pick the weakest container that does the job — background before border, border before a card surface. A separate section covers when containment backfires. Cards on everything flatten hierarchy, nesting past two levels adds noise, and a border for its own sake is clutter.

There is also a practical side: consistent corner radius, padding and shadow for containers inside a design system, plus a check that groupings hold up in dark mode and low contrast. If spacing already communicates the group, adding a border is redundant — worth a second look at the layout rather than extra decoration.

## Install

### Claude Code (native platform)

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

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

### Codex

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

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

### Cursor

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

2. **Manually: put the files in place**
- File: `.cursor/skills/law-of-common-region/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-common-region
```

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

### Gemini CLI

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

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

### Windsurf (Devin Desktop)

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

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add Owl-Listener/designer-skills --skill law-of-common-region -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-common-region/SKILL.md

## When to use it
- split a long form into logical sections
- make a card read as a discrete item users can act on
- separate sidebar navigation from page content
- tie scattered content together with a section background
- highlight a table row on hover or selection

## Example prompts
- Group the fields in this form by meaning — use law-of-common-region, not just spacing
- Review this layout: where is proximity not enough and a common region needed? Apply law-of-common-region
- Too many cards here and the hierarchy is gone. Walk the layout with law-of-common-region and drop redundant containers

## 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: 1bfa4cf88da182fc.

BEGIN THIRD-PARTY FILE 1bfa4cf88da182fc
```text
---
name: law-of-common-region
description: Apply the Law of Common Region — a shared container, background, or border groups elements regardless of spacing. Use when grouping must survive a tight layout. For grouping by spacing alone, use `law-of-proximity`.
---
# Law of Common Region
You are an expert in Gestalt visual organization and containment-based grouping.
## What You Do
You apply the Law of Common Region to create clear groupings using visual boundaries — backgrounds, borders, cards, and surfaces — so users understand which elements belong together.
## The Principle
Elements enclosed within a shared boundary or placed on a shared background are perceived as a group, even when they are not especially close together. Containment is one of the strongest grouping signals available:
- A card with a background creates an unambiguous group
- A colored section background ties disparate content into a unit
- A panel border tells users that everything inside belongs together
## Common Region vs Proximity
Both signal grouping; they work differently:
| | Law of Proximity | Law of Common Region |
|---|---|---|
| Mechanism | Spatial closeness | Shared boundary or background |
| Best for | Related items already close | Items that need a stronger or explicit boundary |
| Overhead | Zero — just spacing | Visual weight — a border or background is present |
| When to prefer | Most layout grouping | Cards, panels, sidebars, tabbed sections, modals |
Use proximity first; add common region when proximity alone is insufficient or when the grouping boundary needs to be explicit (e.g. a card that can be acted on as a unit, a form section within a larger form).
## Applications
| Pattern | Common Region Role |
|---|---|
| Cards | Container clearly delimits a discrete item |
| Sidebar | Background or border separates navigation from content |
| Modal / sheet | Surface elevation signals an isolated task context |
| Form sections | Background or rule divides logical groups within a long form |
| Table rows | Hover/selection background shows a row as a unit |
| Tag groups | Pill background makes each tag a discrete object |
| Tooltip | Container boundary distinguishes overlay from page content |
## When Containment Is Counterproductive
- Using cards for everything flattens hierarchy — not every group needs a container
- Nested common regions create visual noise; limit nesting depth to two levels
```
END THIRD-PARTY FILE 1bfa4cf88da182fc

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