Nice game! I love to gather the enemies to one side of the screen by slapping them, and then do the normal attack, stun locking all of them until they die. This strats won't work for the boss tho.
Thanks for playing! I'm happy you found the "slap" ability fun to use, it's one of my favorites too! If I expand the game later, I've got ideas for making the slap ability key to a more complicated boss battle. :D