Catchy and fun
Really gives a lot of energy and psyches one up. Very appropriate for a first boss theme, as one would expect the first boss to be the first 'serious' battle, yet simple and relaxing enough to have fun in.
I'd know, since I played the game and it was exactly the feeling it gave me which prompted me to just finish the rest of the game.
You have great talent. Keep up the good job. :)