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GSAP · 19 Reduced-Motion Alternatives
Series contents · Technology map
Stage: Input and accessibility · Editable example · Storage ID: gsap-step-19
Goals and learning outcomes
- Learning outcome: explain the role of User Preference. Input case: three step transitions.
- Deliverable: a table of step content and button operation. Explain the rationale for handling Immediate State, connecting it to the code.
Prerequisites
Prepare the exercise results on Equivalent Operation and Focus from Unit 18, “Keyboard Step Navigation”.
Key concepts and explanations
User Preference
Reduced motion signals that large movements should be reduced. It does not mean removing the information itself.
Immediate State
Apply the final state even when motion is skipped. Functionality placed only in a completion callback may be missed.
Practice setup
First check the execution scope guidance on the example screen. The following environment is for extending the assignment in a separate project. The existing gsap-01·02·03 are starting examples. Write new units in a separate local GSAP project. The gsap-02 preview uses native scroll events; install and register ScrollTrigger in an external project. Preserve CSP and iframe isolation.
The linked example is a starting point. It does not implement every task below. Complete work beyond its supported scope in a separate project.
Practice tasks
- In src/day-19.js of a separate practice project, apply final styles with gsap.set in the reduced-motion branch. Refer to the existing Unit 1·14·28 examples only as starting points.
- Input conditions: three step transitions. Baseline: 180px. Run under baseline conditions, then record observations and errors in notes/day-19.md.
- Variable: Movement Distance; changed value: 0px. Run again using the same input path. Deliverable to save: a table of step content and button operation. Hypothesis to check: Content and completion state are preserved. Compare with the actual results and record whether they agree and the causes of any differences.
Variables to observe
| Variable | Baseline | Change | Expected change / hypothesis |
|---|---|---|---|
| Movement Distance | 180px | 0px | Content and completion state are preserved. |
Predictions in this table are not measured results. Change one condition at a time and record why the actual result differs.
Completion criteria
- Required deliverable: a table of step content and button operation. Include results for both baseline and changed conditions so that a total of 2 conditions can be compared, and record the inputs and execution environment together.
- Connect all of these concepts in the explanation of the difference between the two conditions: User Preference, Immediate State. For items that differ from expectations, give at least 1 cause or reason they remain unresolved.
Self-check
- Which processing stage does User Preference affect in this exercise? Input case: three step transitions.
- Variable: Movement Distance. Hypothesis to check: Content and completion state are preserved. Did the actual results match the hypothesis? Explain the evidence in terms of Immediate State.
Official references
Linked example and execution scope
Example source · Runtime environments and limits
This is an experiment on Reduced-Motion Alternatives. It supports direct interaction and cleans up the resources it uses.
Source code and records are not overwritten automatically. Resetting an existing example also preserves your notes.
Next learning
Previous: Keyboard Step Navigation · Next: Completion Callbacks and Interruption