Apple Design — Interaction Logic (how it behaves, not how it looks)

The functional decision layer: which navigation, which state behavior, how it responds, and why. This is the technical/functionality half of Apple design — what makes an interface feel right beyond how it looks. Reach here for behavior decisions; reach for apple-design-motion for the animation that executes them and apple-design-os for the components they configure.

When to use

• Choosing navigation/presentation: push vs sheet vs modal vs tab vs popover vs split-view vs full-screen.
• Designing state behavior: loading/empty/error/disabled, optimistic updates, pull-to-refresh, pagination.
• Tuning perceived performance / responsiveness.
• Handling focus, keyboard, input, hit targets, pointer-vs-touch.