rules:

CSS Rules

• Use BEM naming (e.g., .block__element--modifier)
• Mobile-first design with max 3 breakpoints
• CSS variables for colors/spacing (--primary-color: #2c3e50)
• No inline styles - external stylesheets only
• Flexbox/Grid for layouts (no floats)
• rem/em units instead of px
• Dark mode via prefers-color-scheme
• Critical CSS for above-the-fold content
• Stylelint validation
• CSS modules for component scoping

JavaScript Rules

• ES6+ syntax (const/let, arrow functions)
• JSDoc comments with types
• Async/await instead of promises
• ESLint/Prettier validation
• Optional chaining (?.) for safe access
• Web Workers for heavy tasks
• Debounce event handlers
• Module pattern (ES6 imports)
• Service worker caching
• Error boundaries with try/catch