Games must engage players by keeping them in the game flow. Tobetter define the game difficulty according to the player, GeneticAlgorithms can be used. One of the interesting characteristics ofGenetic Algorithm is that it is a non-deterministic algorithm. For theplayer’s vision, it means that enemies are unpredictable. By notknowing which NPCs he will face, the gameplay turns moreinteresting. Another amusing factor for gaming is its adaptability,causing NPCs to slowly struggle to find a way to beat the player. Thesetwo characteristics make Genetic Algorithms good tools to makegames more entertaining. This paper aims to demonstrate thisadaptation capability in the Survival Shooter, developed by Unityenterprise and modified by the author for the algorithmimplementation. As result, it shows that players could stay in the gameflow while playing against genetically modified enemies.