Slot maths built to be signed off
Slot Clarity builds the mathematics, game design and playable prototypes behind slot games, for studios and operators. Every model is simulated, documented and explainable, so your own review and the test house have what they need first time.
What we build
Game design
A documented concept your team can build from: mechanic framework, feature logic, paytable structure and UX flow.
Mathematical modelling
A full maths model to your RTP targets, with statistical outputs, simulation results, the back-end model source code and a documented build.
Prototyping
A playable Unity prototype running on the real maths, delivered as a hosted WebGL build behind a login.
Nothing touches your pipeline until handover
Every model is built on our own simulation framework, a Java back end with a Unity front end that plugs directly into it. We build, simulate and test on our side, in parallel with your team, and hand over a finished package: model source code, a documented build, documentation, prototype. The framework itself stays with us. Your engineers integrate on their own schedule. There is no shared repo to police and no half-built feature sitting in your codebase waiting on us.
You deal with one person, and that person is the one doing the work. No account manager, no handoff to a junior.
The maths has to be right
Use the arrow keys to step through the points. Every point is also listed in the table that follows.
| Spins | Simulated RTP | Lower bound | Upper bound |
|---|---|---|---|
| 10,000 | 98.48% | 91.03% | 105.92% |
| 12,589 | 94.91% | 88.62% | 101.20% |
| 15,849 | 96.56% | 90.81% | 102.32% |
| 19,953 | 95.83% | 90.74% | 100.92% |
| 25,119 | 96.47% | 91.88% | 101.06% |
| 31,623 | 97.43% | 93.21% | 101.66% |
| 39,811 | 95.78% | 92.14% | 99.42% |
| 50,119 | 95.91% | 92.66% | 99.16% |
| 63,096 | 95.54% | 92.67% | 98.41% |
| 79,433 | 96.20% | 93.62% | 98.77% |
| 100,000 | 96.50% | 94.19% | 98.81% |
| 125,893 | 97.79% | 95.67% | 99.91% |
| 158,489 | 97.06% | 95.18% | 98.93% |
| 199,526 | 96.34% | 94.69% | 97.99% |
| 251,189 | 97.21% | 95.72% | 98.69% |
| 316,228 | 97.10% | 95.78% | 98.42% |
| 398,107 | 96.62% | 95.46% | 97.79% |
| 501,187 | 96.47% | 95.44% | 97.51% |
| 630,957 | 96.03% | 95.11% | 96.94% |
| 794,328 | 95.94% | 95.13% | 96.75% |
| 1,000,000 | 95.94% | 95.21% | 96.66% |
| 1,258,925 | 96.15% | 95.50% | 96.80% |
| 1,584,893 | 96.00% | 95.42% | 96.58% |
| 1,995,262 | 96.04% | 95.52% | 96.55% |
| 2,511,886 | 96.00% | 95.55% | 96.46% |
| 3,162,278 | 96.13% | 95.72% | 96.54% |
| 3,981,072 | 96.21% | 95.84% | 96.58% |
| 5,011,872 | 96.11% | 95.78% | 96.43% |
| 6,309,573 | 96.08% | 95.79% | 96.37% |
| 7,943,282 | 96.04% | 95.78% | 96.30% |
| 10,000,000 | 96.05% | 95.81% | 96.28% |
| 12,589,254 | 96.04% | 95.83% | 96.24% |
| 15,848,932 | 96.07% | 95.89% | 96.26% |
| 19,952,623 | 96.08% | 95.92% | 96.24% |
| 25,118,864 | 96.07% | 95.92% | 96.21% |
| 31,622,777 | 96.07% | 95.94% | 96.20% |
| 39,810,717 | 96.05% | 95.94% | 96.17% |
| 50,118,723 | 96.03% | 95.93% | 96.13% |
| 63,095,734 | 96.02% | 95.93% | 96.11% |
| 79,432,823 | 96.02% | 95.94% | 96.11% |
| 100,000,000 | 96.03% | 95.95% | 96.10% |
| 125,892,541 | 96.04% | 95.97% | 96.10% |
| 158,489,319 | 96.01% | 95.95% | 96.07% |
| 199,526,231 | 96.01% | 95.96% | 96.06% |
| 251,188,643 | 96.02% | 95.97% | 96.07% |
| 316,227,766 | 96.03% | 95.99% | 96.07% |
| 398,107,171 | 96.02% | 95.98% | 96.05% |
| 501,187,234 | 96.01% | 95.97% | 96.04% |
| 630,957,344 | 95.99% | 95.96% | 96.02% |
| 794,328,235 | 95.99% | 95.97% | 96.02% |
| 1,000,000,000 | 96.00% | 95.97% | 96.02% |
A slot can look finished and still be wrong. The RTP drifts from the certificate, the volatility does not match the pitch, the bonus pays out in a way nobody modelled. These are the problems that cost months, not the design.
So every model we deliver comes with the numbers that prove it: RTP by component, hit rates, max win and its frequency, volatility, and the simulation that produced them. You can check our work. Your test house can check our work. That is the point.
We also build games we are prepared to put our name to. Win potential is what it says it is, and we do not build mechanics designed to mislead the player. If a design brief asks for one, we will say so and suggest something that does the same job honestly.
What we do
Services, taken singly or together. Every engagement is scoped and quoted after a discovery call, so you get a fixed price for your game rather than a rate card for a generic one.
Game design
A documented concept your team can build from: mechanic framework, feature logic, paytable structure and UX flow. Specific enough that a developer can pick it up without asking what we meant.
- Mechanic framework
- Feature logic
- Paytable structure
- UX flow
Mathematical modelling
A full maths model to your RTP targets, with statistical outputs, simulation results, the back-end model source code and a documented build. Documented to the standard a test house expects, so the questions they ask are already answered.
- Full maths model to your RTP targets
- Statistical outputs and simulation results
- Back-end model source code
- A documented build
Prototyping
A playable Unity prototype running on the real maths, delivered as a hosted WebGL build behind a login. Play the game before you commit a production team to it.
- Playable Unity prototype
- Runs on the real maths
- Hosted WebGL build behind a login
Development assistance
Senior support through production: answering the maths questions your developers will have, reviewing the implementation against the model, and keeping the shipped game faithful to the one that was signed off.
- Answers to your developers' maths questions
- Implementation reviewed against the model
- The shipped game kept faithful to the signed-off one
Iterations
Changes after delivery, scoped by what moves: design only, design and maths, or design, maths and prototype.
- Design only
- Design and maths
- Design, maths and prototype
Audits and second opinions
If you have a model you want checked before it goes to certification, or a design whose maths you are not sure about, ask. We will tell you what we would need to look at and what it would cost.
- Models checked before certification
- A second opinion on a design's maths
Process
Discovery call
Bring the concept, the brief or the problem. If we are not the right fit, we will say so.
Fixed quote
A discovery call ends with a fixed quote, sent within 3 working days.
Build and simulate
We build, simulate and test on our side, in parallel with your team.
Handover package
We hand over a finished package: model source code, a documented build, documentation, prototype.
Lewis Stephens, founder

I have spent around ten years in slot mathematics and design, at Gamesys, Gold Coin Studios and Yggdrasil, before starting Slot Clarity in March 2024. I have sat on the studio side of certification enough times to know exactly which questions the test house will ask, and I build so that the answers are already in the document.
Games I have worked on include:
Tikitopia BoosterBelt
Aloha Gaming
Devour The Weak
Yggdrasil
Monopoly Bank It
Gamesys
Rainbow Ryan 2
Yggdrasil
Mega Moolah Lucky Bells
Gold Coin Studios
Bouncy Bubbles
Gamesys
When you hire Slot Clarity, you get me.
Frequently asked questions
Do you sign an NDA?
Yes. Send yours or we will send ours, and we can sign before the discovery call if you want to talk about an unreleased game. Everything you share is treated as confidential either way. Unreleased work is never named publicly, and a game only appears in our track record once it is live.
Who owns the model, source code and prototype?
You do. The maths model, the code written specifically for it, the documentation and the prototype build are yours on final payment, to use, change and certify as you see fit. What stays with us is the tooling: the simulation framework the model runs on and the Unity front end that drives the prototype. Where the model relies on part of the framework, the documentation explains how that part works, so your engineers can reproduce its behaviour in your own engine without needing ours.
How does handover and integration with our engine work?
Nothing touches your pipeline until handover. We build, simulate and test on our own framework, then hand over one package: the maths model and the code written specifically for it, a documented build, the maths documentation (RTP by component, hit rates, max win and its frequency, volatility, and the simulation results behind each figure), documentation of how the parts of our framework the model uses actually work, and the prototype. The framework itself stays with us. Your engineers integrate on their own schedule, in your own engine. If you want us alongside them while they do, development assistance covers it: we review the implementation against the model so the shipped game matches the one that was signed off.
How long does a typical engagement take?
It depends on scope, which is why the quote follows the call. As a guide, a maths model to agreed RTP targets takes 3 to 5 weeks, and design through to a playable prototype takes 8 to 12 weeks. The quote states the timeline for your game, and if anything moves it you hear from us before it does.
What are your payment terms?
Fixed price, invoiced in stages at the milestones set out in the quote, so you pay as the work is delivered. Invoices are due within 30 days. The deliverables transfer to you on final payment.
What happens if the certified RTP does not match the model?
The handover package exists so this is caught before certification, not after: every figure comes with the simulation that produced it, so your team and the test house can check it. If a test house result still differs from ours, we find out why. If the difference is in our model, we fix it at no cost to you. If it is in the implementation, we show your engineers exactly where the two diverge, under development assistance if that is in place, or as a scoped piece of work if it is not.
Do you work with start-up studios?
Yes, and a first title with no maths lead in the building is where we are most useful. You get a model documented to the standard a test house expects without hiring for it, and a fixed quote before you commit. The discovery call is the same whether you are a two-person studio or an operator commissioning an exclusive.
Start with a call
A discovery call ends with a fixed quote, sent within 3 working days. We work out what you actually need, whether that is one service or the full chain, and price it for your game. Bring the concept, the brief or the problem. If we are not the right fit, we will say so.
Or email hello at slotclarity.co.uk