I liked this game overall- so much of it worked well! The spritework was great and expressive, and the music was catchy and felt very GameBoy. I also really liked using nose smoke to indicate when the dragon was recharging its flame.
One friction point I ran into was that using rocks to kill knights was difficult, not just because of the timing, but because their pathing appears to be entirely random. In cases where I had less fire breaths than there were knights, I was just waiting for some of the knights to overlap or for them to walk under an area where I could crush them. For most levels generated this worked okay, but in others, it resulted in enough waiting think that I felt inclined to just restart, which was a bit of a shame. If the knights had the ability to 'pursue' the dragon, even for a short time, this might make them more threatening and allow the player to guide them under rocks easier.
Also, I did run into a case where I spawned into a level without any knights and couldn't find any way to progress to the next level.
That said, these were just nitpicks, and since it is a very arcade-y experience, the only thing lost by those issues were high scores, not game progression, so they weren't super big deals. Overall, really great entry!