MERLIN STUDIO
VENTURE DOSSIER

Sapien

Human movement, understood

A movement app for everyday people. It assesses how you move, finds what limits you, builds a programme around it, then re-tests. Every test and drill is shown on a 3D body, not described in a paragraph.

DOSSIER

  1. 01Why Merlin wanted to build it
  2. 02The partnership
  3. 03The product
  4. 04Product decisions
  5. 05How it is built
  6. 06Evidence and progress
01 · WHY MERLIN WANTED TO BUILD IT

Most fitness apps hand out workouts. Very few tell you why your heels lift in a squat, or whether anything changed. Sapien is built around that loop: find the limit, train it, measure it again.

02 · THE PARTNERSHIP

Merlin-originated. Merlin saw the opportunity, designed the method and built the product end to end: the app, the 3D body, the movement engine and the content. The clinical review and the market-side partner are the next pieces to put in place.

  • 01127 commits in just over two weeks
  • 02Method, product and 3D body all designed and built by Merlin
  • 03Web, iOS and Android from one codebase
03 · THE PRODUCT

Live on the web at sapien.fitness, with iOS and Android builds from the same code. Assess, trace, train, re-test. Plus Mind: short resets where the body on screen acts out each instruction.

Visit Sapien
The Sapien session player: a 3D figure doing a scapular push-up, 10 reps, set 1 of 3
One session player for everything. The body shows the move.

A visual baseline

Six quick self-tests, from toe touch to rotation, score what your body can do today.

Why does this happen?

Describe a fault, like heels lifting in a squat. A map of the body ranks likely causes, then 30-second tests narrow them down.

A programme that adapts

Workouts and mobility built around your limits, in sessions from 15 minutes to an hour.

Shown, not described

Every drill plays on a 3D body, with the floor, a box or a bar where it should be.

Coach

Ask about a movement, or ask for a session. Answers come from a reviewed movement database.

Mind

Resets for real moments, like I feel tense or I can't switch off. The body acts out each step.

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CAPTURED FROM THE CURRENT BUILD · SAMPLE PROFILE

The Sapien home screen: a 3D figure, a mobility score of 33 and today's session
Home: today's session, your score, and a nudge to re-test.
Ankle detail: the figure doing a knee-to-wall test, 32 degrees available against a 34 degree target
Each joint in plain numbers: what you have, what you need.
A trace test: the figure reaching overhead, with the current lead cause shown
Why does this happen? Short tests narrow the cause.
The programme's workouts tab: a 29 minute full body session with six movements
Workouts that train your limits, in 15 to 60 minutes.
The programme's mobility tab: week one, a half-kneeling ankle rock on the figure
A mobility plan, week by week.
Mind: a seated figure guiding an I feel tense reset, with a 1:23 timer
Mind: situation-first resets. Bring mind back to body.
Coach: ask about movement, learn, or build a session
Coach: ask, learn, or build a session.
04 · PRODUCT DECISIONS
01

The AI never decides

The app reaches the conclusion. The model only maps free text to fixed lists and phrases what is already known. Words like diagnosis or cure are blocked, and a failed check falls back to reviewed copy.

02

No sign-up wall

It opens offline, with no account. An anonymous account is made quietly, and your history can be added to but never overwritten.

03

The re-test is the product

Two weeks on, you are asked to test again. That comparison is the reason to come back, and the number the product is measured on.

04

Private by construction

Nothing loads before consent. Session replay stays off, because it would record someone typing their symptoms.

05

Movement it owns

The body, the rig and the motion model are Sapien's own. Borrowed model weights were taken out, and a test fails if one comes back.

05 · HOW IT IS BUILT
  • React 18
  • Vite
  • TypeScript
  • Three.js
  • Capacitor 8
  • Firebase
  • Gemini
  • Python + PyTorch
  • Blender
  • Playwright

Pose is an output

A movement starts as intent and constraints. A solver places the body, and the rig only renders. Nobody hand-types joint angles.

A body built by script

Two humanoids, generated in Blender from an open base mesh, on an 82-bone rig with measured joint centres.

1,219 tests

Across the app, the engine and the content. The motion service is tested to receive a movement request and nothing about the person.

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06 · EVIDENCE AND PROGRESS

Live on the web and free to try without an account. Physiotherapist review and the app store releases are in progress. Outcome data will be published once there is enough re-testing to be honest about.

Know a market this could serve?

Coaches, clinics, gyms, a community that moves. If you have the route to people, the evaluator will work out what the product side could be.

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