Folsom Prison slot is a follow-up release by NoLimit City, where most positions on the grid are 'behind bars' at the start of each spin. This slot game has a 4-6-6-6-4 grid with 16 to 46,664 win ways, and different symbols are unlocked by landing wilds, scatters, xSplit, or xWays symbols on adjacent positions. Players can enjoy the atmosphere and soundtrack of the game, which is entirely different from its predecessor, SQ.

The regular symbols include 5 inmate premium symbols, two wild symbols - the regular wilds and cockroach nest wilds - that substitute pay symbols to complete wins. The innovation of this game is the Cockroach feature, where the starting position of the cockroach nest always turns wild, and cockroaches walk around to add multipliers to random positions. The multipliers can be x1, x2, x3, or x10. Cockroaches also open locked positions, and the multiplier values they award increases by +1 if they split.

The bonus rounds in Folsom Prison are called 'Walk the Line Bonus' and 'The Chair Bonus' rounds. 'Walk the Line Bonus' triggers after landing three scatters in view, and it awards eight free spins. The default grid is 2-4-4-4-2. For every spin, the game awards a minimum of one cockroach nest wild unleashed. Players get upgraded to the 'Chair' tier once they land a single scatter, where they get a chance to purchase more free spins. 'The Chair Bonus' triggers with four scatters in view, and players receive eight free spins on a 4-4-4-4-4 grid. The game awards three minimum cockroach nest wilds per spin.

Players can access the Bonus Buy feature by clicking on the yellow star on the left side of the screen, but it is only available outside the UK. In the Bonus Buy feature, players can buy 'Walk the Line' for 68x their stake with 96.36% RTP and 'The Chair' for 1,500x their stake with 96.31% RTP. There are also three lucky draw random options that players can choose from, with prices ranging from 82x to 784x depending on the feature odds.

Overall, Folsom Prison is an enjoyable and innovative slot game where players can unlock positions in the grid by landing symbols. The games' mechanics and features are easy to understand, and the atmosphere of the game is fantastic. The game's innovative Cockroach feature provides an exciting gaming experience with excellent winning possibilities. With two bonus rounds available, players can enjoy eight free spins and a 4-4-4-4-4 default grid in 'The Chair' bonus round, and a minimum of one cockroach nest wild per spin in 'Walk the Line' bonus round.