“Op Art” is a category — or kind — of art. I did it in high school. It takes a fair amount of imagination and exactitude. Usually it it makes sole use of black and white, with imaginative high contrast images. Not the case here. Yes, I understand the simple take on the concept. Not a bunch of controls, easy to use. But Sylwester, you must have ...some! Line quality, background choices, axes choices, resolution…At least an expectation that one would get more than one size of square, line, or color. Can’t remember what I paid for it, but the function and UI are abysmal. On the app description, the term “kill time” is emphasized. Look at the art samples and see if this is how you would make an impression on someone you like. Lettibg them know how you 'kill time.' Maybe his first try at an app. I was hoping for a bit more. Maybe it’s free by now. Cheers.