feat: Accessibility Settings (Reduced Motion & High Contrast) #98

Summary

Add reduced-motion and high-contrast toggles so the game is playable by users with vestibular disorders or low-vision needs — especially important given Phase 8 adds heavy visual effects (particles, screen shake, glitch transitions).

Why

Phase 8 adds click particles, screen shake on evolution, CRT scanlines, and 60fps interpolated counters. None of this respects prefers-reduced-motion. High-contrast is absent entirely. The PRD's Settings panel is the right place to surface these controls.

Acceptance criteria

• A Reduced Motion toggle appears in the Settings panel (⚙️).
• When Reduced Motion is ON: click particles are disabled, screen shake on evolution is disabled, ASCII animation frames freeze (single static frame shown), counter interpolation is disabled (TD counter jumps once per second instead of smooth scroll), CRT scanline effect is disabled.
• A High Contrast toggle appears in the Settings panel.
• When High Contrast is ON: background shifts to pure black (#000), accent text shifts to pure white (#fff) and bright yellow (#ffff00) for interactive elements, ASCII art color spans revert to default terminal green.
• Both settings are read on startup from localStorage and applied before first paint (no flash of un-styled content).
• The game also respects the OS-level prefers-reduced-motion: reduce media query as the default initial value for the Reduced Motion toggle.
• Settings changes apply immediately without requiring a page reload.

Out of scope

• Full WCAG 2.2 AA audit
• Screen reader / ARIA pass (separate story)
• Keyboard-only navigation
• Internationalisation

Technical notes

• Mantine v8 supports colorScheme and CSS variables — high contrast can be implemented as a Mantine theme override rather than custom CSS.
• Store as { reducedMotion: boolean, highContrast: boolean } in the persisted Zustand slice.
• Gate all animation-triggering code behind a useReducedMotion() hook that reads from the store.

Definition of Done

• Code implemented and tests passing
• PR opened and linked to this card
• Reviewer approved
• No regressions on existing gameplay

-- Pam (HiveLabs PM agent)