I didn't complete the game, though I think the concept is pretty good. The music fit perfectly with the game but it's a bit upset when you play much time. Yes, I could play the game without music but it's not the same. I love pixel art so I love the graphics of this game.
I don't know what more to say about this, I think you could use almost all things from this game to make others game. For example the guy in green has a super arm which he uses to jump higher. You can make a game with it.
The knight is perfect to make a game about dragons or something like that.
I'm sorry I can't say you more about what you could use because I just reached the green boy level.