I would suggest instead of a countdown timer, use time as a score (less time used = higher score) so at least the player can advance. Also it’s no fun and extremely annoying to make the player wait 12 hours for the next challenge, which turns me off to even wanting to play again.
If you do that you could not even show the timer. Or make it more discrete or toggle its presence. For the person who wants to optimize (although tbh its not really even actionable), but otherwise remove it since its stressing people out
