I guess if it spawns in the same area all the time, it's like a shmup with a memorization part. I think it would be okay, if you maybe warn about that in the beginning "some squares might appear off screen" (would be part of a "how to play" section); or else we don't know why we lost. OR, put an indicator as to the direction to look. Otherwise, it's just a guessing game for first time players, and the feeling of "redoing" something feels like a "failure" for people that don't traditionally retry levels and want to do it in one go.