law-of-common-region
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.
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/owl-listener/designer-skills --skill law-of-common-region- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads law-of-common-region automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
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
- A border for its own sake adds clutter; if proximity already communicates the grouping, the border is redundant
Best Practices
- Give containers consistent corner radius, padding, and shadow within a design system
- Use the weakest container that gets the job done — background before border, border before card surface
- Ensure common regions survive in low-contrast or dark mode contexts
- Don't combine proximity and common region redundantly on the same grouping unless you are establishing hierarchy (a card inside a panel section, for example)
FAQ
What does the law-of-common-region skill do?
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.
How do I install law-of-common-region?
Run npx skills add https://github.com/owl-listener/designer-skills --skill law-of-common-region in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/law-of-common-region/ (personal) or .claude/skills/law-of-common-region/ (project).
Which AI agents can use law-of-common-region?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is law-of-common-region safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains law-of-common-region?
It is published by owl-listener in owl-listener/designer-skills. It has 1,764 recorded installs.
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