I've been playing this game for about eight years now and have loved it since I first downloaded it. Recently I learned it's impossible to obtain certain units after a collab is over, that has to be the dumbest mechanic I've ever heard. A GAME ABOUT COLLECTING AND USING UNITS DOESN'T LET YOU HAVE ALL OF THEM UNLESS YOU PLAY THROUGH EVERY *TIMED* COLLABORATION EVENT. I will continue playing because I enjoy the gameplay but this really needs to be fixed somehow.