If you have a pointed question feel free to ask here
It seems like the main menu UI doesn't function on all possible window layouts with smaller ones making the confirm button too small. That button also doesn't match the theme of the game, so feels a bit out of place. Same with the gameplay. If I expand / de-expand the game, I am finding that some of the UI can either get too big, too small, or in the wrong place. I'd start by solving that issue. For this reason I can find on my big screen monitor the player health becomes really small and in the corner, making it harder to read during gameplay. You could consider putting the health on the player sprite to make it super obvious.