Big Bang Boom

NetEnt's Big Bang Boom pairs a high-volatility 4,300x ceiling with a grid that grows as you play: a base-game spin opens on four reels of four symbols and expands upward and downward as covered rows are revealed, pushing the number of ways to win from 256 up toward a maximum of 10,000.

That expansion is why base-game wins stay narrow — three rows of covered positions wait above the starting grid and three more below it, opening only when a winning symbol touches them vertically or a bomb blast reaches them directly, so every hit lands as three or four of a kind rather than anything longer.

Bomb symbols replace the usual wild in Big Bang Boom, and seven kinds appear across the game. Several clear along a single line running through their own square: one wipes up and down, another left and right, another the four diagonal corners, and a fourth all four sides at once. Two more work on a wider or more random footprint — one detonates everything adjacent to it regardless of direction, and another opens up a handful of covered spots at random during the base game, switching to setting off a handful of random unclaimed spots once free spins start. The last bomb variety is locked to the free spins round alone; once it lands it keeps re-detonating on every following spin until that round finishes. A bomb blast or a completed win both set off the Avalanche mechanic, clearing the reels involved and letting new symbols drop into the space before checking again for further hits.

On the paytable, four card ranks from J to A form the low end, worth 0.16x to 0.2x the bet for a four-symbol combination. Four character icons sit above them for the premium tier — crown, heart, smiley face and butterfly, in yellow, purple, blue and green respectively — paying 0.4x to 1x for the same four-of-a-kind result.

Free spins arrive once the reels reach their full ten-position height, handing out six spins on a 4x10 grid that can widen out to 8x10 with extra reels joining either flank. Landing spots during the round are restricted to flat-value prizes and bomb symbols; any prize that lands stays locked in place, and each bomb blast that touches a locked prize doubles it, up to a 2,048x limit, with every locked value totalled once the spins are gone. A Treasure Prize can also turn up whenever a covered spot opens, in the base game or the bonus alike, sometimes worth a fixed 16x, 32x or 64x, or one extra spin, when it happens during free spins.

Skipping ahead to the feature costs 75x the stake for a standard set of six free spins, or 150x for six spins that begin with the free-spins-only bomb already sitting on the reels. Big Bang Boom carries a 96.07% RTP at its richest setting (four lower alternatives run down to 88.10%), high volatility, a 4,300x maximum win, and a betting range of 0.25 to 100 per spin; NetEnt released it on 19 September 2023.