I liked the idea!
I liked the idea of switching ammo types and defeating enemies by matching the correct ammo type, but I think creating certain places in the map for the player to change ammo type is not a good approach to the mechanic. I think, being able to change ammo on certain beat intervals of the music or even by key press or powerups on the way would be a better implementation.
Apart from those, the visuals are great and I think you have an overall interesting approach to the theme and geometry limitations. I enjoyed the game!
Good job!