The demo physically can't cheat.

Joints clamp to normative range of motion. Contact limbs are solved, not drawn.

JavaScript is off, so the annotated demo below is static: a cobra stretch, palms and toes pinned to the floor by inverse kinematics, elbow bent at roughly 149° at the top of the lift.

1Elbow — 149°
computed, never authored
2Palms
pinned — position solved by inverse kinematics
3Floor
hard constraint — nothing passes below

Cobra Stretch — real engine output, replayed live 65 exercises verified the same way

The checklist every exercise passes

Before an exercise ships, a headless script runs the movement engine through its full cycle and checks it against physics — not a demo reel, the same script that runs in this repository.

Pins hold through the whole cycle
A planted hand, foot, or knee stays where it's planted, frame to frame.
Nothing sinks below the floor
Every joint stays at or above y = 0, in every frame of every exercise.
Body segments never pass through each other
Soft-tissue contact is fine. A limb's axis crossing another limb's axis is not.
Every joint stays inside clinical range of motion
Each of the 30 degrees of freedom is clamped to a normative goniometric limit.
Every body profile re-verified
Average, Petite, Tall, Long legs, Broad — all five re-run against the same checks.
Goldens: every animation snapshot-compared on every change
If a code change moves a joint anywhere it wasn't meant to, the build fails.

Range of motion, the clinical way

30clinical degrees of freedom

65exercises built from them

9starting postures

Every joint moves on clinical degrees of freedom, expressed in degrees using the standard goniometric convention a physio would write on a chart, and clamped to normative range-of-motion limits. Spinal flexion isn't authored on one vertebra — a spinal rhythm distributes it across the lumbar, thoracic, and cervical segments, the way an actual spine shares the load.

What we don't claim

HONESTY BOX

Said plainly, on a landing page

Muscle activation percentages are clinically authored estimates, not EMG measurements.
This is an educational tool, not medical advice.
No testimonials on this page — there aren't any customers to quote yet, and we'd rather show you the engine than write one for them.

See it on your own exercise

Inspect any exercise →

Open any of the 65 exercises and scrub the timeline yourself — the same pins, the same floor, the same clamp, every time.