Motion & Interaction Engine
A centralized interaction architecture connecting tokens, GSAP, ScrollTrigger, Lenis, Motion, pointer capability, reduced motion, and symmetric cleanup.
- Type
- Internal Engineering
- Focus
- Motion, input, accessibility, lifecycle
- System
- Shared interaction engine
- Status
- Integrated and verified
Why this system needed to exist.
The production experience required expressive motion across navigation, storytelling, system diagrams, pointer response, and route changes. Implementing each effect independently would create conflicting timings, duplicated event loops, and inaccessible behavior.
The engineering problem.
Without a shared engine, scroll effects, pointer response, page transitions, and component animation can compete for state and frame time. They can also hide content, displace keyboard focus, or ignore user motion preferences.
Boundaries shaped the architecture.
- 01No scroll-jacking or essential animation
- 02Stable content when JavaScript or animation is unavailable
- 03Reduced-motion and coarse-pointer modes
- 04Keyboard focus must not inherit magnetic displacement
- 05One global smooth-scroll and cursor lifecycle
A controlled path from problem to proof.
- 01
Define shared timing, distance, easing, and stagger semantics.
- 02
Use GSAP and ScrollTrigger for narrative sequences and Motion for local interface response.
- 03
Run one Lenis instance only for full-motion, fine-pointer environments.
- 04
Make reduced-motion, coarse-pointer, focus, and lifecycle states part of the engine contract.
Responsibilities made visible.
The diagram is an ordered semantic list; lines and activation are visual enhancement only.
- 01
Capability
Pointer and motion preferences select full, reduced, or minimal behavior.
- 02
Tokens
Shared durations, distances, easing, and stagger rules constrain every primitive.
- 03
Orchestration
One GSAP loader, ScrollTrigger registration, and Lenis ticker coordinate global work.
- 04
Primitives
Reveal, text, parallax, progress, magnetic, pointer-light, and cursor components remain opt-in.
- 05
Cleanup
Listeners, animation frames, triggers, contexts, tickers, and instances have symmetric disposal.
Decisions expressed in the build.
Lazy orchestration
GSAP and ScrollTrigger load in the browser only when a consuming primitive needs them.
Single scroll loop
Lenis is driven from the existing GSAP ticker instead of introducing another permanent animation loop.
Local high-frequency state
Pointer and scroll response use refs, MotionValues, and CSS variables rather than React renders per event.
Accessible final states
Reduced motion clears decorative transforms and leaves every content region visible.
What was chosen—and why.
Centralized semantic motion tokens
- Trade-off
- Individual sections cannot choose arbitrary timing or easing.
- Reason
- A controlled vocabulary keeps interaction coherent and makes behavior easier to audit.
GSAP for narrative; Motion for local UI
- Trade-off
- Two libraries require explicit ownership boundaries.
- Reason
- Each tool is limited to the work it handles clearly, avoiding overlapping animation control.
Preference-aware global providers
- Trade-off
- Full effects are intentionally unavailable on some devices.
- Reason
- Content stability, input compatibility, and user preference are more important than visual parity.
Tools mapped to responsibility.
- GSAP
- Coordinated narrative and component timelines
- ScrollTrigger
- Viewport and normalized progress orchestration
- Lenis
- One preference-aware smooth-scroll instance
- Motion
- Local springs and UI response
- React
- Lifecycle boundaries and reusable primitives
- CSS
- Stable static states, focus, and reduced-motion protection
Evidence, without extrapolation.
A reusable motion layer now coordinates reveal, scroll, pointer, route, and component behavior through one bounded vocabulary.
Reduced-motion testing left zero hidden reveal or text items; coarse-pointer testing removed cursor, smoothing, and parallax dependencies.
The documented 60-event pointer and scroll sample recorded zero Long Task entries, while repeated route cycles retained one cursor and one Lenis provider.
Decisions that carry forward.
- Motion quality depends as much on lifecycle ownership as it does on easing and timing.
- Reduced motion is a complete interaction mode, not a final CSS override.
- Magnetic and cursor effects should remain optional responses around native controls.
Connected engineering studies.
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