The game, called "The Catcher'', was developed for robotic rehabilitation in combination with single Degree of Freedom (DoF) robots. The game is then used to perform the difficulty balancing experiments using Evolutionary Algorithm (EA) and other EA to optimize the coefficients of the objective function of the first EA. The objective of the player in "The Catcher'' is to control the squirrel (game character) towards falling hazelnuts (target object). The player should direct the character to collect as many objects as possible during a therapy session. The character only moves in the horizontal axis of the screen - corresponding to the flexion of the wrist (palmarflexion) or wrist extension (dorsiflexion).