Update: I've emailed for support on the issue in my original comment below, but had no response. I've therefore dropped my rating (sadly) to one star. Very interesting game for people who work a lot with colour. Unfortunately most of the (numerous) ads don't fit themselves to the screen properly on my S21 Ultra so cannot be closed ('X' button presumably off the edge of the screen). I have to close the entire app and restart it to play another game 😕