button-states

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• SKILL.md

SKILL.md (first lines)

# Button and Interactive Element States

Every interactive component must have a complete, visually distinct state for each interaction mode. Missing or ambiguous states make the UI feel unfinished and reduce user confidence.

## The Six States

| State | Trigger | Visual signal |
|---|---|---|
| **Rest** | Default | Base colour, cursor: pointer |
| **Hover** | Mouse over | Slightly darker, subtle background shift |
| **Active / Pressed** | Mouse down / tap | Noticeably darker, slight scale-down |
| **Focus** | Keyboard navigation | Visible focus ring, no change to fill |
| **Disabled** | Not available | Low contrast, cursor: not-allowed, no interaction |
| **Loading** | Async action in progress | Spinner or pulse, non-interactive |

## Deriving State Colours Algorithmically

State colours are not chosen independently — they are derived from the base colour by adjusting lightness in HSL. This guarantees coherence across the entire palette.

```
base:     hsl(H, S%, L%)
hover:    hsl(H, S%, L% - 8%)    ← darken 8%
active:   hsl(H, S%, L% - 14%)   ← darken 14%
```

### Example: primary button `#635BFF` (hsl 243, 100%, 68%)

```css
.btn-primary {
  background: hsl(243, 100%, 68%);       /* rest    #635BFF */
}
.btn-primary:hover {
  background: hsl(243, 100%, 60%);       /* hover   #4A40FF */
}
.btn-primary:active {
  background: hsl(243, 100%, 54%);       /* active  #3429FF */
}
```

For light buttons on dark backgrounds, invert the logic — lighten on hover instead of darkening.

### Secondary / outlined buttons

```css
.btn-secondary {
  background: transparent;
  border: 1px solid var(--color-border);
  color: var(--color-text);
}
.btn-secondary:hover {
  background: var(--color-grey-100);     /* subtle fill */
  border-color: var(--color-grey-300);
}
.btn-secondary:active {
  background: var(--color-grey-200);
}
```

## Focus State

Focus is a keyboard navigation requirement (WCAG 2.2). It must be visible and must not rely on the hover style alone — keyboard users do not trigger hover.

```css
.btn:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 3px;
}
```

- Use `outline`, not `box-shadow`, for focus rings — `outline` respects `border-radius` in modern browsers and does not affect layout
- `outline-offset: 2–4px` gives the ring breathing room from the component edge
- Never use `outline: none` without a replacement focus style

## Disabled State

```css
.btn:disabled,
.btn[aria-disabled="true"] {
  opacity: 0.4;
  cursor: not-allowed;
  pointer-events: none;
}
```

- Disabled elements are exempt from WCAG contrast requirements — low opacity is correct and intentional
- Use `pointer-events: none` to prevent click events even if JS is bypassed
- Do not change the shape or size of a disabled button — only colour and cursor change

## Loading State

When a button triggers an async action, replace the label with a spinner and prevent re-submission.

```css
.btn--loading {
  pointer-events: none;
  opacity: 0.7;
}
```

**The cursor does not change while loading.** It signals affordance, not progress: the arrow for ordinary content, `pointer` for something you can act on. Progress belongs to the element and the loading region, which the user is already looking at, rather than to wherever the mouse happens to rest. `cursor: wait` is also inert next to `pointer-events: none`, so the rule reads as deliberate while doing nothing.

- Keep the button width stable during loading — avoid layout shift when label is replaced by spinner
- Return to rest state on completion (success or error)
- For long-running operations, pair with a status message — a spinner alone does not tell the user what is happening

## Scale on Active (Optional)

A subtle scale-down on press adds physical feedback — borrowed from Disney's squash principle.

```css
.btn:active {
  transform: scale(0.97);
  transition: transform 80ms ease-out;
}
```

Keep the scale value between `0.95–0.98`. Below `0.95` feels like the button is breaking.

## Complete Button CSS Reference

From dembrandt/dembrandt-skills, MIT.

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