Add Component Skill

Usage

/add-component <ComponentName>

Step 1: Ask Questions

1. Check Existing Components First

Does an existing component cover ~80% of the need?
→ Check src/ui/components/ before creating new

Existing: ArcadeButton, BasePetCard, GeminiIconButton, Modal, ProgressBar, SegmentedControl, SeeMore, SoundPicker, Tab, TeamListItem

2. Component Purpose

Brief description (1 sentence):

3. Configuration Options

What options does it need?
- Required: ___________
- Optional with defaults: ___________
- Event handlers: ___________

4. Sprites

Does it display game sprites? → MGSprite.toCanvas()

5. Dynamic State

Does it need reactive updates?

A) Manual setters only (setLabel, setDisabled, setValue, etc.)
B) Reactive to Globals (subscribe to myInventory, currentTile, weather, etc.)
C) Both

If B/C: Component subscribes to Globals and auto-updates UI
→ Remember to unsubscribe in destroy()!

6. Child Components (IMPORTANT)

Does this component need sub-components?
→ REUSE existing components, never recreate!

Available:
- ArcadeButton, GeminiIconButton → Buttons
- Modal → Dialogs/popups
- ProgressBar → Progress indicators
- SegmentedControl → Tab-like selection
- Tab → Tabs
- SoundPicker → Audio selection
- BasePetCard, TeamListItem → List items
- SeeMore → Expandable content

Example: A "SettingsPanel" component might use:
- SegmentedControl for sections
- Toggle for on/off settings
- ArcadeButton for actions

---

Step 2: Create Structure

src/ui/components/<ComponentName>/
├── <ComponentName>.ts      # Logic + factory function
├── <componentName>.css.ts  # Styles (CSS string)
└── index.ts                # Re-exports

Read existing components for templates: src/ui/components/*/

---

Step 3: Required API

Options Interface

export interface <ComponentName>Options {
    // Required (no default)
    label: string;

    // Optional (have defaults)
    variant?: 'primary' | 'secondary';
    disabled?: boolean;

    // Event handlers
    onClick?: () => void;
}

Handle Interface

export interface <ComponentName>Handle {
    root: HTMLElement;           // REQUIRED
    set<Property>(value): void;  // Public setters (minimal)
    destroy(): void;             // REQUIRED - cleanup
}

Factory Function

export function create<ComponentName>(options: <ComponentName>Options): <ComponentName>Handle

---

Step 4: Style Rules

Theme Tokens (REQUIRED)

/* NO hardcoded colors */
background: var(--color-bg);
color: var(--color-text);
border: 1px solid var(--color-border);

Responsive (REQUIRED)

min-height: 44px;        /* Touch-friendly */
width: 100%;             /* Flexible, not fixed */
max-width: 300px;        /* Constraint if needed */

Scoped Styles

/* Prefix all classes with component name */
.component-name { }
.component-name__label { }
.component-name--variant { }

---

Step 5: Register

Export → src/ui/components/index.ts

export { create<ComponentName> } from './<ComponentName>/<ComponentName>';
export type { <ComponentName>Options, <ComponentName>Handle } from './<ComponentName>/<ComponentName>';

---

Step 6: Validate

Required

• root: HTMLElement in Handle
• destroy() removes ALL listeners/observers/intervals
• Factory function returns Handle

Styling

• Uses CSS variables (no hardcoded colors)
• Touch-friendly (min 44px targets)
• Flexible widths (not fixed px)
• Focus states visible (:focus-visible)

Composability

• Safe to nest inside other components
• No global CSS (scoped classes only)
• Styles injected into root, not document.head
• Reuses existing components (never recreate Button, Modal, ProgressBar, etc.)
• Child components' destroy() called in parent's destroy()

If using Sprites

• Uses MGSprite.toCanvas() (never hardcoded paths)

If using Globals (reactive)

• Subscribes in factory function
• Unsubscribes in destroy() (memory leak otherwise!)
• Updates UI elements on subscription callback

If using Child Components

import { createProgressBar, createArcadeButton } from '../index';

// In factory:
const progressBar = createProgressBar({ ... });
root.appendChild(progressBar.root);

// In destroy:
destroy() {
    progressBar.destroy();
    root.remove();
}

If using Globals (reactive UI)

import { getMyInventory } from '../../../globals/variables/myInventory';

// In factory:
const unsub = getMyInventory().subscribe((inventory) => {
    // Update UI when inventory changes
    updateItemCount(inventory.items.length);
});

// In destroy - CRITICAL!
destroy() {
    unsub();  // Unsubscribe from Global
    root.remove();
}

---

References

• Rules: .claude/rules/ui/components.md
• Existing components: src/ui/components/*/
• Theme tokens: src/ui/theme/
• Reuse workflow: .claude/workflows/ui/component/reuse-existing-component.md