Ok, I'm going to add the option to free up some CPU by removing the stars in the background. (Also, this could be because all of the collisions/camera movement are made by me (TIC-80 doesn't have them built-in like other game engines) and they have some bugs.
EDIT: You can now press A to toggle stars. It doesn't seem to be reducing lag to much though, maybe I'll try something else in a while.