How we test a slot's math: 600,000+ rounds per game, 96.50% RTP

Before one of our games gets art or sound, we want to know exactly what it pays, how often and how unevenly. This post explains how we find that out, and what the numbers on our game pages mean.

Every round exists before you spin

A slot on Stake Engine does not invent a result when you press spin. Its math is a table of finished rounds, with every symbol drop, tumble and free spin already played out, and each round has a weight. When you spin, the server picks one round at random in proportion to those weights, and the game shows it to you.

We build those tables by simulation. For every game we play out and store more than 600,000 complete rounds across its four modes: 908,780 for Kaiju Snack, 641,312 for Stompkin and 641,158 for Rust Rook. Every mode gets at least 120,000 of them, so rare outcomes are really in the table, not just in a formula.

RTP is computed, not estimated

Because the table is the game, its return to player (RTP) is not a guess from a sample. It is the weighted average payout of every round in the table, divided by what the mode costs. We tune the weights until that number is 96.50% in every mode: the base game, the 2× mode that makes free spins more likely, and both bonus buys. We chose one number for every mode, so no way of playing returns more than another in the long run.

Put the other way round, the game keeps 3.50% of everything wagered on it, on average, over a very large number of rounds.

What RTP says about your next spin: nothing

This is the part worth repeating. Every spin is drawn independently, with the same odds, whatever came before. A long dry spell does not make a bonus "due", and a big win does not make the next spin colder. RTP describes the whole table over millions of rounds. Over a session of a hundred or a thousand spins, your result can land far above or far below it.

Hit rate

Hit rate is the share of rounds that pay anything at all. In the base game it is 28.5% for Kaiju Snack, 29.3% for Stompkin and 32.0% for Rust Rook, so roughly one spin in three. Two caveats. A "hit" includes wins smaller than the bet, so it is not the chance to come out ahead. And the single most common outcome in all three base games is a spin that pays nothing: 68 to 72% of spins.

Volatility

Two games with the same RTP can feel completely different. Volatility describes how unevenly the return is spread: steady small wins, or long quiet stretches broken by rare large ones. We measure it as the standard deviation of a round's payout, in multiples of the bet. Our three base games sit between about 11.5 and 13.5, which is the uneven kind.

In practice, most of the return comes from uncommon rounds, mainly the free spins features: Rampage, Hallow Night and Night Shift. In Rust Rook's base game, the spins that do not trigger Night Shift return about 52% of their cost; the remaining 44.6 points of the 96.50% come from the feature, which triggers about once in 213 spins on average. Stompkin's Hallow Night arrives about once in 224.

Max win

Each game caps what a single round can pay: 10,000× the bet in Kaiju Snack, 15,000× in Stompkin and Rust Rook. The platform requires the cap to be reachable, and it is, but rarely: in the base games of Stompkin and Rust Rook it is about one round in seven million. Most players will never see it.

How we check a table

A table is only as good as the code that played it.

• An independent checker. A second program, written from the published rules alone and sharing no code with the generator, replays every stored round and must agree with the table on every payout.
• The platform's rules. Exact RTP in every mode, at least 100,000 rounds per mode, no gaps between win ranges and a reachable max win.
• Real rounds. We play rounds through the finished game and compare what the screen shows with the stored result.
• Stake. It checks the files again on upload and reviews every game before release.

Why we publish this

A slot is entertainment with a price, and these numbers are that price, measured: a one-in-three hit rate that is mostly small wins, a feature every couple of hundred spins, and a long-run return of 96.50% that no single session has to match. If a game stops being fun, stop playing.

The art side of the work has its own post: drawing Jack in code.

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