About

Slot machines operate on a weighted pseudorandom number generator where each symbol carries a distinct probability weight. A cherry symbol might appear with probability 0.25 while a jackpot 7 appears at roughly 0.03. The theoretical Return-to-Player (RTP) - the fraction of wagered money returned over infinite spins - typically sits between 92% and 96% for commercial machines. This simulator implements that math directly: a cumulative distribution function maps a uniform random draw r ∈ [0, 1) to symbol indices weighted by real payout tables. Five paylines are evaluated across a 3×3 grid - three horizontal rows plus two diagonals.

Misunderstanding slot volatility costs real money. High-variance machines pay rarely but large; low-variance ones pay often but small. This tool lets you observe long-run statistics without financial risk. Note: client-side Math.random() is a PRNG (not cryptographically secure), so this approximates but does not replicate hardware RNG chips found in regulated machines. The house edge is baked into the weight table. Over 10,000 spins, your balance will converge toward the configured RTP. Pro Tip: track your hit frequency in the stats panel - it exposes the volatility profile directly.

Formulas

Symbol selection uses a weighted cumulative distribution. Given total weight W = n∑i=1 w_i, generate uniform random r ∈ [0, W). Select symbol k where:

k−1∑i=1 w_i ≤ r < k∑i=1 w_i

Expected Return-to-Player over N spins:

RTP = N∑j=1 payout_jN∑j=1 bet_j × 100%

Where w_i = weight of symbol i, n = total number of distinct symbols, r = uniform random draw, payout_j = winnings on spin j (bet × multiplier, or 0), bet_j = wager on spin j. The wild symbol acts as a universal substitution: when evaluating a payline, a wild in any position is treated as the highest-paying symbol present on that line.

Reference Data

Symbol	Weight	Probability	3-Match Payout	2-Match Payout	Variance Class
🍒 Cherry	25	25.0%	2×	1×	Low
🍋 Lemon	20	20.0%	3×	1×	Low
🍊 Orange	18	18.0%	4×	1.5×	Low-Med
🍇 Grape	14	14.0%	6×	2×	Medium
🔔 Bell	10	10.0%	10×	3×	Medium
⭐ Star	5	5.0%	20×	5×	High
💎 Diamond	4	4.0%	40×	8×	High
7️⃣ Seven	3	3.0%	75×	10×	Very High
🃏 Wild	1	1.0%	Substitutes any symbol		Jackpot
Paylines: Row 1 (top), Row 2 (middle), Row 3 (bottom), Diagonal ↘, Diagonal ↗
Total Weight Sum		100	Theoretical RTP: ~94% (varies with bet pattern)
Hit Frequency: ~28% of spins produce a payout across 5 paylines

Frequently Asked Questions

A uniform random picker gives each of 9 symbols equal probability (~11.1%). The weighted system assigns cherry a 25% chance and seven a 3% chance. This creates a realistic payout curve: frequent small wins maintain engagement while rare jackpots create the variance profile that defines slot volatility. Without weighting, the RTP would be far too generous or the payouts would need to be artificially low.

The configured weight table and payout multipliers target approximately 94% RTP. However, due to variance, you need roughly 10,000+ spins before observed RTP converges to the theoretical value. In short sessions (under 100 spins), actual returns can range from 50% to 200% - this is normal statistical fluctuation, not a bug.

The 3×3 grid produces 5 lines: top row (positions 0,1,2), middle row (3,4,5), bottom row (6,7,8), diagonal top-left to bottom-right (0,4,8), and diagonal bottom-left to top-right (6,4,2). Each line checks for 3-of-a-kind first (highest payout), then 2-of-a-kind from left. Wild symbols substitute for any other symbol. Multiple paylines can win simultaneously on a single spin.

No. Bet size is a linear multiplier on payout amount only. The RNG weights are constant regardless of wager. A 1-credit bet on a 3× cherry match pays 6 credits. A 10-credit bet on the same match pays 60 credits. The probability of that cherry match is always 1.5625% (0.25³) for a single payline.

Slot variance (standard deviation of returns) is high relative to the edge. With a 6% house edge but a payout multiplier up to 75×, individual sessions exhibit wild swings. This is by design - it makes the game feel winnable in the short term. The law of large numbers only guarantees convergence over thousands of trials. Your stats panel tracks this convergence in real time.

Yes. The wild has a 1% probability per cell (weight 1 out of 100). On a 3×3 grid with 9 independent draws, the chance of at least one wild appearing per spin is approximately 1 − (0.99)⁹ ≈ 8.6%. When a wild lands on a payline, it adopts the identity of whichever symbol produces the highest payout for that line.