Reduced motion first terminal animation

SKILL: Reduced-Motion First Terminal Animation

Domain: terminal-ui Trigger: Build any animation that should stay dormant until the user explicitly opts into motion. Source Pattern: Distilled from reviewed terminal rendering, layout, animation, and accessibility implementations.

Core Method

Read the local reduced-motion preference before spawning timers and treat null as “paused.” Hook animations into a single clock that can unregister itself whenever the animation is hidden, so the loop never races multiple independent timers while respecting accessibility.

Key Rules

• Evaluate get initial settings prefers reduced motion (or equivalent) on mount and refuse to start motion if true.
• Share one clock (e.g., use animation frame) so every animation breathes in sync and can be paused by passing null.
• Never queue set timeout when reduced motion or pause is active; return the last drawn frame instead.
• Resume from the current global time when motion becomes allowed again so there is no jump.

Example Application

When animating a loading spinner in a toolbar, wire the spinner to the shared clock and keep it frozen until the user unsets prefers reduced motion; the rest of the layout retains its state, and the spinner returns to the proper frame without rewinding.

Anti-Patterns (What NOT to do)

• Starting independent timers before checking reduced-motion and then canceling them later.
• Letting each animated component manage its own clock, which prevents pausing all motion with a single flag.
• Resetting animation timelines when motion resumes, which causes jarring jumps.