Dr. Zappo

Dr. Zappo is a Hacksaw Gaming slot set for release on September 29, 2026, running a 5-reel, 4-row grid with 14 active paylines. The theoretical RTP is 96.31% at its default tier, volatility is medium, and the win cap is 10,000x the bet. This review is based on the game’s finished demo build and Hacksaw Gaming’s own listing ahead of launch, and will be updated once it goes live at operators.

The setting is Electric City, a cartoonish mad-scientist world built around Dr. Zappo and his sidekick Mr. Brain, mid-experiment on a beast that turns out to be the source of the game’s core mechanic: eyeball symbols that land on the bottom row and shoot straight up or diagonally across the grid.

Wild Eyeballs

Every eyeball symbol shoots in one of three directions, straight up, diagonally left, or diagonally right, and any paying symbol it passes through transforms into a Wild. Some of those Wilds carry a multiplier, ranging from 2x up to 200x, and multiple multiplier Wilds connecting in the same win stack their values together. Energy Fields sit at the edges of the grid, and an eyeball that strikes one bounces back into play, continuing to transform symbols or add to existing Wild multipliers rather than simply leaving the grid.

Free Spins and Buy Bonus

Landing 3 or more Scatter symbols triggers the free spins bonus. Four Buy Bonus tiers sit in the purchase menu: BonusHunt FeatureSpins at 3x the bet makes every spin 5 times more likely to trigger a bonus naturally, ZigZag Zappo FeatureSpins at 100x guarantees at least 2 Eyeball symbols land on the activated spin, Eyeconic at 50x buys 10 free spins with an increased chance of Eyeball symbols, and No-Brainer at 200x buys 10 free spins in which eyeballs shoot in two directions at once instead of one.

Dr. Zappo Review

Dr. Zappo turns a fairly simple payline format into something genuinely mechanical through the eyeball-shooting system, since the direction each eyeball fires and whether it bounces off an Energy Field both matter to how much of the grid ends up converted to Wilds on a given spin. Stacking multiple multiplier Wilds in one win is where the real upside sits, and the Energy Fields’ bounce-back behavior means a single eyeball landing in the right spot can end up transforming considerably more of the grid than its starting position alone would suggest. The four-tier Buy Bonus menu gives players a genuinely useful range of options rather than one flat price, from BonusHunt’s cheap odds nudge up to No-Brainer’s guaranteed two-direction shooting, which is clearly the strongest of the four given it doubles the eyeball mechanic’s reach for the entire round. Medium volatility at a 10,000x cap is a reasonable pairing for a mechanic built on stacking multipliers rather than one single huge trigger, and the cartoonish mad-scientist presentation, complete with Mr. Brain as comic relief, keeps Dr. Zappo feeling lighthearted even as the eyeball mechanic does some genuinely intricate work underneath it. Electric City itself adds a bit of personality most eyeball-and-lab slots skip entirely, giving the whole release a clearer identity than its mechanics alone would carry.