How slots are made
An Engine studio spends most of its time on the maths rather than the art: every mode gets simulated up to a million times, every round is stored, and the weights get nudged until the RTP lands inside the platform's band. Then the game is released, and for most studios very little happens. Of the 646 new Engine games in one week of November, 372 had fewer than 100 players.
| Step | What happens | What comes out |
|---|---|---|
| 1. Idea | Theme, characters and the one mechanic that sets the game apart | A short concept |
| 2. Math model | Symbols, paytable, features, modes and what each mode costs | Game config and game logic |
| 3. Simulation | Each mode played 100,000 to 1,000,000 times | Books: one stored round per line |
| 4. Weighting | Weights shifted until RTP, hit rate and max win odds hit the target | A lookup table per mode |
| 5. Art and sound | Symbols, backgrounds, animation, music, effects | Assets |
| 6. Front end | The web game that plays a stored round out on screen | Game build |
| 7. Review | Maths, front end, rules text and replays checked, then a star rating | Approval or a list of fixes |
| 8. Live | Players, bets and turnover show up in public data | Engine Insights |
Steps 3 and 4 follow the Engine math SDK structure and math requirements. Studios may also bring their own math and front end (Engine docs).
The math model
Everything that decides money lives in the math model: the symbols, the paytable, when a feature fires and what each mode costs. Engine's simulator plays it through and keeps each finished round. A mode then ships as two files, one listing what happens in every round, the other giving each round a weight and a payout.
| Lookup table | Weight changed | RTP | Rounds that pay | Top payout (5,000x) |
|---|---|---|---|---|
| Every round at weight 1 | none | 97.83% | 36.0% | 1 in 100,071 |
| Losing rounds weighted up | x1.022 | 96.50% | 35.6% | 1 in 101,451 |
| Rounds of 100x and more weighted down | x0.973 | 96.50% | 36.0% | 1 in 102,816 |
Own toy example, 12 Nov 2026. Ten payout groups from 0x to 5,000x, made up for the demo, not from a real game. All weights start at 1, as in the Engine math SDK. Real optimisers work on far more groups and targets at once.
Our toy run in the weighting table came out at 97.83%, and getting it down to 96.50% meant changing how often each stored round gets picked, with nothing in the paytable touched. Whether we made losing rounds a bit more likely or the 100x-plus rounds a bit rarer, the share of paying rounds moved by less than half a point. Engine's reviewers mostly push back on the extremes, a base game that hardly ever pays or a max win you'd need more than 10 million bets to see.
| Check | What the Engine docs ask for |
|---|---|
| Simulations | 100,000 to 1,000,000 per mode for slot-type games |
| Max win | Realistically reachable, typically more often than 1 in 10,000,000 |
| Hit rate | Non-zero wins about 1 in 20 bets or more often |
| Losing rounds | 90,000 non-paying rounds out of 100,000 may be grounds for rejection |
| Gaps | Wins must exist between the small payouts and the top one |
| Rules text | Return and max win stated per mode, matching the uploaded tables |
| RTP band | Every mode inside the platform band, see note |
From the math requirements in the public docs repo (March 2026 version) and the review checklist. The repo version gives an RTP band of 90.0% to 98.0% with all modes within 0.5% of each other. The live approval guidelines, read 6 Nov 2026, give 96.0% to 96.7% for every mode of a new game. In the bonushunt.gg Engine catalogue, 83.6% of 7,776 games list an RTP from 96.00% to 96.99% (read 12 Nov 2026).
Art, sound and the front end
Nothing you see on screen decides anything. The front end is handed a finished round, basically a list of what happens in order, and its job is to make that list look and sound like a slot. Getting the timing right eats a surprising amount of the build, how long a tumble hangs before the win counter rolls, how long the big-win screen stays up. Engine has a web SDK built on PixiJS and Svelte for studios that want one.
Pop Parade is our own game. There a swap without a line is undone at no cost, so a round is only drawn once a line forms.
Review and approval
- Reviewers recompute return and top payout from the uploaded tables and compare both with the rules text.
- They play every mode and open replays of wins, big wins, max wins, losses and bonus triggers.
- Three anonymous reviewers score the game from 0 to 3. The average becomes the star rating, which decides whether it goes live and where Stake shows it.
After launch
| Players in 30 days | Games | Share |
|---|---|---|
| Under 10 | 1,053 | 14.0% |
| 10 to 99 | 2,875 | 38.3% |
| 100 to 999 | 2,415 | 32.2% |
| 1,000 to 9,999 | 1,045 | 13.9% |
| 10,000 and more | 111 | 1.5% |
Data: Engine Insights, 30 days, 13 Oct to 11 Nov 2026 (UTC). Fetched 12 Nov 2026. 7,499 games with real-money play, our own left out. Grouped by us. 17 games took half of all turnover (3,576,519,675 USD in the window). New games 5 Nov to 11 Nov 2026: 646, of them 372 under 100 players.
Most launches on Engine stay tiny, and over the whole month 3,928 live games out of 7,499 had fewer than 100 players, and the median game had 87. Open Engine Insights on day two of your launch and look at players, not turnover, because one high roller can make a dead game look busy.
Starting a slot studio
- Maths. Someone who can write a game model and read a simulation report. Engine's math SDK is in Python.
- Art and sound. Reviewers score quality, creativity and polish, and that score sets the stars.
- Front-end code. A web game that runs on phones and desktops and plays any stored round correctly.
- A platform. On Engine the studio's share is 10% of GGR, paid out each month (Easygo).
- Time for review rounds. Every fix goes back through the checks.
Get the maths through the published checks before anyone draws a final symbol. A feature somebody already animated is wasted work if the simulation drops it, and a pretty game whose base mode pays too rarely still gets sent back.
Not affiliated with Easygo, Stake or Engine. Game names belong to their owners.
Questions
How are slot results decided online?
On Stake Engine every possible round is simulated before launch and stored with a weight. Each bet draws one stored round at random, in proportion to the weights. Many other casino games work out each result live, at the moment of the bet.
What is a slot math model?
The full rule set as code: symbols, paytable, features, modes and their prices. Simulating it many times gives the RTP, the hit rate and how likely the biggest payout is.
How many new slots find players?
Few. On Engine, 372 games out of 646 launched in one week of November 2026 had fewer than 100 players, and 17 games took half of all turnover over 30 days.
How do you start a slot studio?
You need maths, art and front-end skills, and a platform that publishes outside studios. On Engine a game passes math and front-end checks plus a star rating from three reviewers before it goes live.
Sources
- Engine docs: overview. static outcome files, weighted selection, own math and front end allowed Checked 12 November 2026
- Engine docs: math SDK game structure. books, lookup tables, all weights start at 1 before optimisation Checked 12 November 2026
- Engine docs: math requirements. simulation count, hit rate, max win reachability, gaps, RTP band (repo version) Checked 12 November 2026
- Engine approval guidelines: math verification. RTP 96.0% to 96.7% for every mode of a new game Checked 6 November 2026
- Engine docs: quality rankings. three anonymous reviewers, 0 to 3 stars, visibility Checked 12 November 2026
- Engine game review checklist. RTP and max win per mode in the rules, replays of wins, losses and bonus triggers Checked 12 November 2026
- Engine math SDK (GitHub) Checked 12 November 2026
- Engine web SDK (GitHub). PixiJS and Svelte Checked 12 November 2026
- Easygo: Stake Engine. 10% GGR royalty, paid monthly Checked 12 November 2026
- bonushunt.gg Engine catalogue. RTP per game, 7,776 games with a value Checked 12 November 2026
- Engine Insights (public API, snapshot). 30 days, 13 Oct to 11 Nov 2026 Checked 12 November 2026
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