Add or remove k dots puzzles
What I call "add or remove k dots puzzles," are puzzles in which some invalid equation is shown, and the goal is to make the equation valid by removing some constant number of dots, k. I have seen exactly two possible moves in such puzzles. I have yet to see a puzzle use both moves. The first type of move I've seen, converts a 1 into the factorial symbol ! by removing a single dot. I have found two puzzles using this move, which you can find here. The second type of move I've seen, converts a 1 into the imaginary unit i, by removing two dots. I have found one puzzle using this move, which you can see here. The last ! in this puzzle could start as a 1, and the instructions could instead be "add or remove 5 dots," so that the puzzle would use both types of moves. Doing so would make the puzzle more challenging, and in my opinion, more interesting.