CSS Standards

CSS Standards

CSS coding standards and patterns for the Oh My Brand! WordPress FSE theme.

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When to Use

• Styling block components
• Writing responsive layouts
• Defining CSS custom properties
• Implementing accessible focus states
• Working with WordPress design tokens

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Reference Files

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BEM Naming

BEM (Block, Element, Modifier) naming convention:

.block                    → Component container
.block__element           → Child element
.block--modifier          → Block variation
.block__element--modifier → Element variation

Block Class Prefix

BEM Examples

/​* Block */
.wp-block-theme-oh-my-brand-gallery { }

/​* Elements */
.wp-block-theme-oh-my-brand-gallery__track { }
.wp-block-theme-oh-my-brand-gallery__slide { }
.wp-block-theme-oh-my-brand-gallery__button { }

/​* Block modifiers */
.wp-block-theme-oh-my-brand-gallery--fullwidth { }

/​* Element modifiers */
.wp-block-theme-oh-my-brand-gallery__button--prev { }
.wp-block-theme-oh-my-brand-gallery__slide--active { }

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Custom Properties

Define custom properties at the block root:

.wp-block-theme-oh-my-brand-gallery {
    /​* Layout */
    --visible-images: 3;
    --block-gap: 1rem;

    /​* Animation */
    --transition-duration: 300ms;
    --transition-timing: ease-out;

    /​* Colors (use theme tokens) */
    --button-bg: var(--wp--preset--color--primary);
    --button-text: var(--wp--preset--color--base);
}

See gallery-block.css for complete example.

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Theme.json Tokens

Use WordPress design tokens from theme.json:

See theme-json-tokens.css for examples.

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Responsive Design

Mobile-first approach using min-width breakpoints:

Example

/​* Base (mobile) styles */
.wp-block-theme-oh-my-brand-gallery {
    grid-template-columns: 1fr;
}

/​* Tablet */
@media (min-width: 768px) {
    .wp-block-theme-oh-my-brand-gallery {
        grid-template-columns: repeat(2, 1fr);
    }
}

/​* Desktop */
@media (min-width: 1024px) {
    .wp-block-theme-oh-my-brand-gallery {
        grid-template-columns: repeat(3, 1fr);
    }
}

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Accessibility

Focus Styles

.wp-block-theme-oh-my-brand-gallery__button:focus-visible {
    outline: 2px solid var(--wp--preset--color--primary);
    outline-offset: 2px;
}

Reduced Motion

@media (prefers-reduced-motion: reduce) {
    .wp-block-theme-oh-my-brand-gallery__track {
        transition: none;
    }
}

Screen Reader Only

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

See accessibility.css for complete patterns.

Color Contrast (WCAG 2.1 AA)

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Stylelint Rules

This project uses Stylelint for CSS linting. Key rules to follow:

No Empty Blocks

Stylelint disallows empty rule blocks. Never create a rule with only a comment:

/​* ❌ Bad - empty block causes stylelint error */
@media (prefers-reduced-motion: reduce) {
    .my-component {
        /​* No styles needed */
    }
}

/​* ❌ Bad - empty block */
.my-component__element {
}

/​* ✅ Good - omit the rule entirely if no styles needed */
/​* (Simply don't include the rule) */

/​* ✅ Good - if you need the media query, include actual styles */
@media (prefers-reduced-motion: reduce) {
    .my-component {
        transition: none;
        animation: none;
    }
}

No Duplicate Selectors

Stylelint disallows duplicate selectors within a stylesheet. Consolidate all styles for a selector in one place:

/​* ❌ Bad - duplicate selector causes stylelint error */
.my-component__number {
    font-size: 2rem;
    font-weight: 700;
}

.my-component__label {
    font-size: 1rem;
}

.my-component__number {
    order: 0;  /​* This duplicates the selector above! */
}

/​* ✅ Good - all styles consolidated in one selector */
.my-component__number {
    font-size: 2rem;
    font-weight: 700;
    order: 0;
}

.my-component__label {
    font-size: 1rem;
}

Hex Color Length

Use shorthand hex colors when possible:

/​* ❌ Bad - can be shortened */
color: #0066cc;
background: #ffffff;

/​* ✅ Good - use shorthand */
color: #06c;
background: #fff;

Key Principles

1. If a rule block would be empty (even with just a comment), do not include it
2. Consolidate all styles for a selector in one place - no duplicate selectors
3. Use shorthand hex colors when all pairs are identical (e.g., #aabbcc → #abc)

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Validation

Always run stylelint after making CSS changes:

pnpm run lint:css

Fix any issues before committing. This ensures consistent code style and catches common errors.

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Related Skills

• html-standards - Semantic HTML structure
• web-components - Frontend Web Components
• native-block-development - Block styling

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References

• BEM Methodology
• WordPress Global Styles
• WCAG 2.1 Quick Reference
• CSS Custom Properties