I didn't understand at first that I was supposed to shoot the big computer mainframe and not the drones, but once I figured that out it was pretty fun. Some of the patterns those drones made were quite difficult to navigate, and I died after getting the final boss to about half HP.
The bosses' designs were cool, and I liked the drones' lasers a lot too. They looked dangerous!
Since you intended for the drones to be immune to the player's attacks, it might have been nice to indicate that in some way. Perhaps a force field flashes when they're hit to show it's being blocked? I'm not sure.