
Beat the clock per round (same timer)
Beat the clock per round (any time remaining gets added to the next round but the difficulty increases or there's less base time in successive rounds)
Final round, you're given all but one digit and several (all but one?) operations so you have to identify the missing digit, operator and potentially the sequence to follow.
( , Tue 29 Aug 2023, 7:38, Reply)

In the NYT version the difficulty definitely ramped up as you went through it. I'm not sure that's the case here.
( , Tue 29 Aug 2023, 10:11, Reply)

For increasing the challenge, I always though a timer starting from your first move would be a good addition. You would challenge yourself to do the math in your head before clicking through the game.
( , Tue 29 Aug 2023, 13:45, Reply)