This game is cool because it presents an interesting dichotomy: do you keep upgrading so that you can kill the dragon faster later or do you just wait for the dragon to die now? It's like a tug of war between the player and game.
The only thing I found lacking in this game is an absence of a lose condition.
Otherwise, it's fun - I myself am a sucker for clickers.
I found the sketchy art charming and vibrant, just like the narrative. Good for them.
The music is good enough.