I really like it! The whole one person has a sword and one person has a shield is rather over done in my opinion, but you actually pulled it off quite well.
While it isn't clear within the gameplay that the green goblins are for the sword and the red for the shield, especially considering the designs of the knights, you've definitely made some fascinating gameplay which I have drawn some inspiration from to use in my own projects.
The choice of font doesn't really work. You've got a very Nordic font when the game is about knights.
It would also be a good idea to give the knights and the castle some visual representation of remaining health.
Overall, fantastic minigame. I do feel like this may work better with some sort of rhythm game element, but great submission!