Design and review Bevy fixed-step 2D physics loops with velocity components, deterministic movement, collision prediction, interpolation, impulses, and tweened presentation.
SkillScore95Maintained
Automatic
◆Coding pack
Last verified 8/16/2026
What it changes
Passed 21 of 22 test cases with the skill, and 19 of 22 without it.
Without skill86%
With skill95%
Checks it passed that the model alone missed
Execute ballistic motion logic inside the FixedUpdate schedule.
Calculate orbit camera movement directly in Update schedule systems using frame delta time.
2 fixed19 passed either way1 still failing0 broke
Pass-rate lift
+9 pp
Tokens
-4%
Agent turns
0%
Response time
-19%
Model gemini-3.6-flashMeasured 8/16/2026v121 of 22 cases passed with skill
Tokens, turns and time describe resource use, not a dollar price.
See it in action
One of 2 test cases the skill fixed. Same model, same prompt, with and without the skill.
1 of 2
Prompt
I have dynamic cannonballs that need predictable, reproducible flight paths regardless of player monitor refresh rates. Should their ballistic motion updates run in `Update` or `FixedUpdate`?
What was checked, without and with the skill
Checked
Without skill
With skill
Execute ballistic motion logic inside the FixedUpdate schedule.
Missed
Passed
case-16 · gemini-3.6-flash · 8/16/2026 · answers are capped and redacted
What's inside
The instructions your model reads when the skill loads.
SKILL.md27 lines2 files
Rust Bevy Fixed Step Physics
Use this skill to separate deterministic simulation from frame-rate-dependent
presentation in Bevy games.
Core Workflow
Identify which movement must be deterministic and collision-safe.
Sample input in update systems, then apply movement in fixed-step systems.
Store velocity, acceleration, and intent explicitly in components/resources.
Predict or sweep movement before committing positions.
Emit physics/collision events; keep animation and particles as presentation.
Interpolate or tween visuals when fixed simulation looks choppy.
Read Next
Task
Load
Fix frame-rate-dependent movement
guidelines.md, workflows/stabilize-physics.md
Add fixed movement and collision prediction
references/fixed-step-patterns.md
Separate animation from physics
references/fixed-step-patterns.md
Source Notes
Guidance is transformed and paraphrased from Herbert Wolverson,
Advanced Hands-On Rust, especially Chapters 7 through 9 on movement,
collision, and smoothing. Examples are original skeletons.