Five reels, four rows. Matching symbols on adjacent reels from the left pay in every combination — up to 1,024 ways.
Brass pistons slam down onto reels 2–4 and nudge to fill the whole reel as one colossal wild. Every piston carries a dial — ×2, ×3 or ×5 — and when several land together their dials multiply: ×3 and ×5 pay ×15.
Every piston feeds the boiler +1 PSI on the gauge above the reels. At 12 PSI the boiler blows: an OVERDRIVE respin fires with pistons on all three middle reels at a combined ×8 — then the gauge vents to zero. Pressure carries over from spin to spin.
Three golden gears (reels 1, 3, 5) award 8 free spins where pistons lock in place for the rest of the feature. A piston landing on an occupied reel upgrades its dial:
Three locked pistons at full upgrade pay ×12 × ×12 × ×12 on every way. Three more gears add 3 spins.
Fire the boiler instantly for 63.4× your bet, priced from the measured value of the feature rather than rounded to a marketing number.
RTP 96.33%, certified over 2,000,000 sequential base spins (the pressure gauge persists between spins, so the base game is simulated as one continuous session) plus 120,000 simulated features. Hit rate 58.3%. Free spins land about once in 156 spins and pay ≈61× bet per feature; the boiler blows about once in 89 spins. High volatility. Wins are capped at 2,500× the total bet. Every symbol is drawn with a cryptographically secure RNG. Demo build — engine, math, art and sound built end-to-end by Zynzio.
Open the throttle: 8 Overdrive free spins with locking pistons and dial upgrades to ×12.
Costs 63.4× your bet · 96.2% RTP on purchase · cost scales with your bet