There are 4 types of balls: Normal (gray), infected (red), recovered (green) and dead (cross). First, there are only normal balls and one infected one. When he touches a normal ball, that ball gets infected too. The light blue zone is the quarantine: Infected balls can't get out of it and normal and recovered balls can't get in it. There's a certain chance an infected ball will die. If an infected ball goes into the hospital, he recovers. Also recovered can turn normal.
100% by @xzscratcher and @yzscratcher !
