Two draws and their greatest common divisor
One paid round draws two independent uniform pockets numbered 0–12. Score is their greatest common divisor, with gcd(0,0)=0. Choose score band 0–4, 5–8 or 9–12 before spinning. All 169 ordered pairs are equally likely.
Exact169-pair enumeration
There are 141 winning ordered pairs for scores 0–4, 16 for 5–8 and 12 for 9–12. For example, draws 6 and 9 have gcd 3, draws 0 and 8 score 8, and draws 0 and 0 score 0. Multipliers use these exact counts, not the number of score labels.
Displayed hit probability and total return
The hit probabilities are 141/169,16/169 and 12/169. Total-return multipliers are 1.150638298,10.14 and 13.52 respectively. A hit returns stake×0.96×169 divided by the selected winning-pair count, including stake; a miss returns zero.
One stake and one settlement
Select a band and virtual stake before starting. One stake is deducted, and both independent draws settle together. Settings, start and refill are locked during the round. A matching GCD score pays the displayed total return; any other score returns zero. There is no mid-round cash-out or additional stake for the second draw.
Local wallet and refill
Settled balance and fractional payout carry persist in localStorage. Reloading during a round ends it without refunding its deducted stake. Outside a round, refill sets 1000 coins when balance is below the smallest stake; it does not add 1000 or erase fractional carry. Band and stake return to defaults on reload.
Expected return and variance
Exact expected return is 96% in every band: hit probability multiplied by the total-return multiplier is 0.96. Bands change hit frequency and variance, not expectation. A 96% expectation is not a promise of a single spin or a short session. This demo does not certify an external operator or reproduce its games.
Technical data and third parties
There are no account, payment or identity-document forms here. Fonts, the visit counter, server and CDN requests can expose technical data including IP and browser details. Complete anonymity, third-party data use and cookie lifetimes are not established. Clearing cache alone may leave localStorage intact.
Frequently asked questions
Is this an operator site?
This independent RK 89 guide supplies its own free Common Factor Roulette demo. Operator identity, domains, licence, apps, payments, support and commercial game equivalence have not been independently verified. No operator account or commercial link is supplied here.
How is the score calculated?
One paid round draws two independent uniform pockets numbered 0–12. Score is their greatest common divisor, with gcd(0,0)=0. Choose score band 0–4, 5–8 or 9–12 before spinning. All 169 ordered pairs are equally likely.
How are bands priced?
There are 141 winning ordered pairs for scores 0–4, 16 for 5–8 and 12 for 9–12. For example, draws 6 and 9 have gcd 3, draws 0 and 8 score 8, and draws 0 and 0 score 0. Multipliers use these exact counts, not the number of score labels.
What return is displayed?
The hit probabilities are 141/169,16/169 and 12/169. Total-return multipliers are 1.150638298,10.14 and 13.52 respectively. A hit returns stake×0.96×169 divided by the selected winning-pair count, including stake; a miss returns zero.
Explore the original free Common Factor game and its score bands.
