Couldn't start the wave, the button didn't do anything. As a project for a beginner to study the unit, it will do. I recommend to deal with the layers of sorting sprites, so that the placed buildings are not on top of the character. Another tip - to make pixel art more pleasing, all objects should be on the same approximately pixel scale. You have large pixels on the background, and small ones on the hero, because he himself is small. Either more of it, or replace the sprite. Good luck.