This is supposed to be the case in the levels before the ones where you program these keywords yourself.
The idea is that you make the "not" keyword without using this keyword (by reading and changing the bits one by one) and then you can start using it. Seems like I should make that clearer in the tutorials and manual 😅 or maybe I'll make them red and cause an error instead to show that these levels aren't supposed to be trivial.
But I do notice on the screenshot that the way the rectangles/UI is drawn is weird, thanks for showing me. I have a fix planned for that.
The AppImage file is to run the game on Linux, you don't need it.