Thanks for your comment! You can actually deselect using the Escape key on PC, or by tapping anywhere outside the buttons on mobile (word "target" is only safe bet though, almost every part of the screen is a button, some of them invisible). And yeah, I agree about the lack of indication for which button you've already pressed.
Going into negative coins is okay; the game only ends once you hit -10.
You might be right about the decimal penalty (it's currently fixed at 3 coins). I was just worried that without it, players could rack up a high score by multiplying and then dividing roughly toward the loop's start, since enough divides push you toward values between 0 and 1, you'd end up pretty close to 2. Maybe it’s still a valid strat if you square some big numbers for free (with tokens), then divide your way back toward the loop’s start.