The framerate is consistent, even when the screen gets filled to the brim with flying bat - balls or Minotaur bots (as you may have gathered, enemy design leaves a lot to be desired). (rotorob.com)
This is followed by a hoppy frog who swings from his tongue, a kangaroo with mad hops, a badger who has claws that let him climb walls, and a sort of flying bat thing with a beak that can do damage. (kitsuga.com)
The wake of small flying bats shows multiple vortices when traced, suggesting that their flight is based on somewhat different principles than that of birds. (science.sciencemag.org)