Big Bang Boom Slot Review
A graffiti-covered brick wall at night, torn flyers pinned along one side and a pink neon sign humming above the reels. That’s Big Bang Boom, and it’s a stranger slot than its street-art swagger suggests: the reels begin as a cramped 4×4 grid on which almost nothing pays, because the game is quietly waiting for its own bombs to knock the wall down. NetEnt have made a slot whose opening minutes are deliberately worse than they look.
It runs at 96.07% RTP with a 29% hit frequency, pays across 256 to 10,000 bet ways and caps wins at 4,300x the bet, with stakes from 0.25 to 100 per spin. The expanding-grid idea puts it in conversation with NetEnt’s own Riches of Midgard: Land and Expand, though the demolition is closer in spirit to Gonzos Quest and its tumbling stones. Seven different bomb types might be invention or clutter.
The Base Game: Expanding Reels and Bet Ways
Every spin starts small. The play area is four reels by four rows, with further positions covered over and waiting. A position gets uncovered when a symbol vertically adjacent to it becomes part of a win, or when a bomb blast reaches it. In the main game the reels can expand to four reels and ten rows; get that far and the free spins round fires.
Wins pay left to right. Matching symbols in any position on three or more adjacent reels, from the leftmost reel onwards, makes a bet way win. Extra instances of the symbol on the same reels create more winning ways, and only the longest combination per symbol is paid.
The way the count works is worth an example. Four Crowns landing as three, two, one and two across reels one to four make twelve winning bet ways: 3 x 2 x 1 x 2, multiplying the symbol counts on each reel. That arithmetic is what stretches 256 ways at the start of a spin to 10,000 once the grid is fully open.
The Avalanche feature is part of the package too: winning symbols go and new ones drop in, which is what keeps a single spin turning into a chain of wins and uncovering more of the wall. It’s the engine behind everything else the game does.
The paytable is small, and the values are multiples of the total bet:
- Crown: 0.40x for three, 1x for four
- Heart: 0.28x for three, 0.60x for four
- Butterfly: 0.20x for three, 0.40x for four
- Smiley: 0.20x for three, 0.40x for four
- A / Q: 0.12x for three, 0.20x for four
- K / J: 0.08x for three, 0.16x for four
Symbol payouts are dynamic, changing with the selected bet value. With a grid this small and pays this flat, the base game isn’t where the money is. It’s where the demolition happens.
Super Bombs: Seven Ways to Demolish a Grid
Seven bomb types is a lot, and they’re the whole character of the game. Four of them can land during spins in the main game and in free spins:
- Vertical Bomb: explodes up and down, removing symbols above and below its position
- Horizontal Bomb: explodes left and right along its row
- Diagonal Bomb: removes symbols at the corners of its position
- Plus-pattern Bomb: explodes in a cross, clearing top, bottom, left and right
Three more are situational. The Persistent Bomb appears only in free spins, blasts everything adjacent to it, then stays on the reels to explode again on every following spin until the round ends. The Omni-directional Bomb takes out all adjacent symbols at once.
The Cluster Bomb behaves differently by mode. In the main game it randomly uncovers three to five covered positions; in free spins it explodes three to five random positions not already holding a bomb.
Free Spins
Open up the full play area in the main game and the round begins: six free spins. Inside them, the grid can go wider still, reaching eight reels by ten rows. Only x1-value Prizes, the four directional bombs and the Persistent Bomb can land on the reels during spins.
The Treasure Prize feature carries the rest. Uncovering new positions during the round turns up Prizes with larger values, different types of bombs, and additional free spins on top of the standard fare.
Treasure Prizes
Treasure Prizes are found whenever new positions are uncovered, in the main game or in free spins. The six bomb types all count as Treasure Prizes, and two more show up only in free spins:
- Large Prize: worth 16, 32 or 64 times the bet
- Extra Free Spin: one additional spin
Prizes that land stay put until the round ends. The multiplier ladder is where the game’s real arithmetic lives: every time a bomb explosion covers a position holding a Prize, that Prize’s value doubles, stepping through x2, x4, x8 and onwards up to a maximum of x2048. A Prize doubled eleven times is a big number sitting on a small grid.
When the round finishes, everything on the board pays out at once. Retriggers arrive through the Extra Free Spin Prize, so a round can keep feeding itself while bombs keep working the board.
Buy Feature
Free spins can be bought at any time, and both options start the round immediately without a base game spin:
- 6 Free Spins: 75 times the bet
- 6 Free Spins with a Persistent Bomb: 150 times the bet, with the bomb placed randomly on the reels at the start of the round
The doubled price for a guaranteed Persistent Bomb is the interesting choice. A bomb that fires on every spin of a six-spin round, doubling every Prize it touches, is doing a lot of work for that extra 75x.
Our Honest Verdict
Overall Rating: 7.7/10
Playing Big Bang Boom means spending a while in a 4×4 room before anyone lets you out. Most of a session is quiet: thin pays, positions slowly coming uncovered, the odd bomb clearing a corner of the wall. The one reason to sit through that is the finish, when the round ends and everything on the board pays at once.
The doubling ladder is the best thing here by a distance. Prizes sticking to the reels while bombs keep multiplying them gives the free spins round a build few games match, and the Persistent Bomb firing every single spin is the detail that makes the round worth reaching.
Its weakness is the opening act. The base game pays so little that it can feel like a queue, and seven bomb types is more vocabulary than the game needs to say what it’s saying. This one’s for players who enjoy a slow build and a payoff that arrives all at once; anyone after steady action in the main game will find the wall stays up too long. It rewards patience beautifully, but only if you bring your own.
Big Bang Boom FAQs
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What is the RTP of Big Bang Boom?
96.07%. -
How does the free spins round trigger in Big Bang Boom?
Fully expanding the play area to four reels and ten rows in the main game awards six free spins. You can also buy the round outright through the Buy Feature. -
What does the Persistent Bomb do in Big Bang Boom?
It appears only in free spins. It explodes along with all symbols adjacent to its position and then stays on the reels, exploding again once on each following spin until free spins end. -
How do Prize multipliers work in Big Bang Boom free spins?
Prizes that land stay until the end of the round. Each time a bomb explosion covers a position holding a Prize, that Prize’s value is multiplied by 2, up to a maximum of x2048. At the end, you win the sum of all Prize values multiplied by the bet. -
How many bomb types does Big Bang Boom have?
Seven: Vertical, Horizontal, Diagonal, Plus-pattern, Omni-directional, Cluster and Persistent. The first four can land during spins in the main game and free spins, the Persistent Bomb appears only in free spins, and the Omni-directional and Cluster Bombs appear in the Treasure Prize feature. -
How much does the Buy Feature cost in Big Bang Boom?
75 times the bet for 6 free spins, or 150 times the bet for 6 free spins with a Persistent Bomb placed randomly on the reels at the start of the round. -
Can free spins retrigger in Big Bang Boom?
Yes. The Extra Free Spin is a Treasure Prize found only in free spins and awards one additional spin. -
What is the hit frequency of Big Bang Boom?
29%.
