One spark. A growing chain reaction. How far can you take it?

Fissionary is a particle-reaction sandbox about experimentation, upgrades, and spectacular chain reactions.

Choose your starting particles, ignite your experiment, and watch your build come alive. Collect the matter it produces, research new possibilities, and discover how different combinations behave.

More growth means more to manage. Heat, cold, and accumulating residue can turn a promising experiment into a catastrophe.

Experiment your way

• Discover eight particle types, each with its own role in your reaction.
• Choose your build and reaction controls to explore different combinations.
• Collect matter and buy upgrades that change how your experiments develop.
• Unlock matter vacuums to help with collection.
• Watch neon particles, electrical arcs, and reaction effects bring your chamber to life.