Thank you!
Stunning them should work, though. The simple enemies need 3 stuns, the knights need 4, and the Beast needs 20 per life. Just to be sure: Did you time your stun attacks with their attacks? When enemies try to hit you and you "attack" during your block when their weapon connects with your shield, it should do the stun. If you see the flashing light, you've successfully stunned them for 1 damage (and you can then bash them to push them into walls for more damage). Otherwise it doesn't do any damage.
If you did stun them with light, then I don't know what sort of random bug occurred and I'm sorry for that :( If you didn't stun them that way, then that's on me for not explaining the mechanics properly, so I'm sorry for that as well :D it's all part of the jam experience lol. Anyway, I'm glad you enjoyed it!