A fun and unique concept, but here's a couple notes.
1) It's possible to skip the trigger in the fourth level that makes the purple things follow you. If you shoot the ball just under the first blue orb on top of its little ledge, you can hit the orb behind it and teleport to it, making the purple things not follow you through the entire level. I mean, I appreciated it because it was stressful enough as is, but I doubt that was intentional. I did it by accident my first time, but then preceded to do it every run thereafter. (Maybe instead of an "on touch" trigger, have a "on stop touch", or just have it be "if(player.x > some_value)")
2) Please let me retract the orb sooner. If I know a shot is going to miss it can be painful to have to wait for it to bounce a few times before retracting. Also, consider binding retract to a different button.
3) You might want to vary the purple things' speed based on where the player is. Imagine it speeding up if it's too far behind and slowing down as it gets closer to camera view. That might make it so the threat is ever-present rather than having the option to speed past it (although, again, the game's pretty stressful as is so idk).