Platform Literacy

Before inventing custom UI, understand the platform's grammar (Apple HIG, Android/Material, Web).

Rules

Prefer native navigation patterns on iOS/Android unless brand requires divergence and you redesign the full stack consistently.
Respect safe areas, status bars, home indicators, notches.
System fonts can be a deliberate choice; custom fonts need fallbacks and performance budgets.
Dark mode is a first-class theme, not an afterthought invert.
Focus rings, Dynamic Type / text scaling, and Reduce Motion are platform features — integrate, don't fight.