Design System Frameworks — the named systems & their rules

A design system framework is a position, not a component grab-bag. Every named system below is opinionated about something — Material about physics and motion, HIG about deference, Carbon about enterprise density, Polaris about merchant content. When you adopt one you inherit its opinions; the friction teams feel is almost always the gap between the system's worldview and theirs. This skill is the field guide: what each system actually believes, the concrete rules that fall out of that belief, and the decision of whether to adopt it, adapt it, or build your own on a headless layer.

The single most important framing: a design system is a set of constraints you're agreeing to. Adopting Material and then re-skinning every component to fight its elevation model costs more than building from scratch. The win comes from picking a system whose opinions you mostly agree with, then theming the parts that are pure brand (color, type, radius, motion personality) while leaving the parts that are pure UX (touch targets, focus order, state layers, a11y semantics) alone.

Platform systems — the OS-backed canon

Material Design 3 / Material You (Google, current: M3 + Material 3 Expressive, 2024–2025)

Philosophy: UI as tactile physical material — surfaces have thickness, cast light, and move with believable motion. M3 dropped literal drop-shadows-as-status for tonal elevation (higher surfaces get a lighter tint of the primary color) and made dynamic color the headline: a single seed (the user's wallpaper on Android, or a brand color) generates a full tonal palette via HCT (Hue-Chroma-Tone) color space. Material 3 Expressive (2025) pushes louder color, larger shapes, springier motion, and emphasized type.