The exact scoring rule
Each round draws two independent readings a and b, each uniformly chosen from 0 to 12. Set n = a + b + 1. Find the smallest prime p greater than or equal to n, then score p − n. If n is already prime, the score is zero: the calculation does not skip to the next strictly larger prime. The possible score values are 0 through 5. The total n ranges from 1 through 25; those totals are not equally likely, even though the 169 ordered reading pairs are.
Three tickets for the same score
Choose a ticket before drawing: Lower accepts scores 0 and 1, Middle accepts 2 and 3, and Upper accepts 4 and 5. There are 169 equally likely ordered pairs of readings. Lower matches 115 pairs, Middle 51 and Upper 3. Each count divided by 169 is that ticket’s hit probability, not the probability that a session will be profitable.
Band multipliers and expected gross return
A matching score returns the captured stake multiplied by 0.96 × 169 ÷ the selected band’s coverage. The gross multipliers are approximately 1.410783 for Lower, 3.181176 for Middle and 54.08 for Upper. A miss returns zero. Each band’s exact expected gross return is 96%; a single round or session can differ from that average.
Examples at different score bands
Readings 0 and 0 give n = 1, prime 2 and score 1, matching Lower. Readings 0 and 1 give prime n = 2 and score 0, also matching Lower. Readings 11 and 12 give n = 24, prime 29 and score 5, matching Upper. Each result still uses the ticket chosen before the round.
Sequential reveals, one captured stake
Select a stake of 10, 20, 50 or 100 virtual coins. The default is 20 with the Lower ticket selected. Starting deducts one stake for both readings. Stake and ticket choices, restoration and another start are locked during the round; the sound control remains available. There are no extra bets, interim collection or automatic repeat rounds. The readings appear in sequence, not as two separate bets. Normally each reveal waits about 420 milliseconds. With reduced motion, each reading is revealed on its next animation frame. The second reveal completes the score and settles the captured stake. Revealing the first reading does not unlock settings or provide a collection opportunity.
Settlement, carry and reload
The raw gross return is the captured stake multiplied by the outcome multiplier. Settlement adds the saved fractional carry to that raw return, then credits only the whole-number part of the sum. The remaining fraction is saved for later settlements. A zero-return round leaves the carry unchanged. The credited return is not a profit payment on top of a separately refunded stake. Reloading before settlement ends the unfinished round without refund, payout or resumption. Its captured stake stays deducted. Previously saved balance and carry remain, while stake selection returns to 20 and the Lower ticket is selected again. Unfinished readings and chosen settings are not saved for continuation. Virtual coins have no cash value.
Frequently asked questions
Do standard roulette red/black rules apply?
No. The demo accepts one of three score-band tickets for a prime-gap score derived from two readings. It has no red/black, number-grid or extra side bets.
What happens when the total n is already prime?
The score is zero. The rule uses the smallest prime greater than or equal to n, so it does not advance beyond a prime n.
Can I collect after the first reading?
No. Both readings belong to one captured stake. The second reveal settles the round, and there is no interim collection.
