Clusters instead of paylines
Reactoonz drops its little alien symbols onto a square grid and pays for touching groups of the same type rather than for lines. When a cluster pays it is removed, the symbols above fall down and new ones drop in from the top, and the grid is evaluated again. A single spin can therefore resolve through many stages.
That cascading structure is the engine of the whole game. Nothing is settled until the grid stops producing clusters, so the difference between a dead spin and a large one is how long the chain keeps going. Pairs of matching symbols also charge meters during a spin, which is how the game's features are fed.
Quantum Leap and the Gargantoon
As clusters resolve, the Quantum Leap mechanic injects wilds into the grid mid-cascade, each with its own effect on the symbols around it. Some clear positions, some transform neighbours into matching symbols, and all of them can start clusters that would not otherwise have formed, extending the chain and compounding the result of one spin.
Filling the game's meter brings out the Gargantoon, an oversized wild that occupies a block of the grid and then splits into smaller wilds as the cascade continues. It is the game's top feature and the route to its largest outcomes, but it requires sustaining a long chain rather than simply landing a symbol.
How it actually plays session to session
Reactoonz is high-variance despite its cheerful presentation. Many spins die on the first evaluation with nothing, and the game's returns depend on the minority of spins where wilds keep arriving and the cascade refuses to stop. The gap between a typical spin and a good one is unusually wide.
It is also busy, which can obscure that. Animations reward near-misses and partial charges as though progress were being made, so tracking actual spend matters more here than in a simpler slot. Play'n GO released it in 2017, and its sequels keep the grid and cascade structure while changing the feature layer.