Really cool premise! The idea of meshing a tower defense and a bullet hell is definitely unique. The pixel art and overall polished aesthetic are excellent, and the whole thing looks like it would be right at home on a game boy color. I did have significant trouble figuring out where to place the buildings. The fact that the grid squares were flashing led me away from the 'H' symbols where the buildings actually needed to be placed. But if you work on a tutorial system and build onto the game with multiple levels/kaijus, this could be truly excellent!