DO
Use #171717 for body text — avoids optical harshness vs pure black
Use shadow-based borders (box-shadow: 0 0 0 1px rgba(0,0,0,0.08)) on cards
Reserve blue accent for exactly one primary action per view
Use 9999px radius only for badges and pills — never standard buttons
Keep motion fast: 150ms micro-interactions, 300ms page-level overlays
DON'T
Use gradients on interactive UI components
Use more than one accent color per view
Apply drop shadows for elevation — use ring-border technique
Mix border-radius families within a single view
Use font weights other than 400, 500, and 600