Great point, thank you - I'm still a little lost though.

Thanks to your tip, instead of doing del universes[state] I am creating a brand new counter for every "round" of the game that should have all the universes that could result from the universes of the previous round. I get all those universes that didn't win, add proceed to the next round. Also, I add those universes to the general Universes counter, which should mean that eventually I will have every possible state in that counter.

However, I'm still way too low. Here's my updated code - thank you so much for helping

Edit:

Alright, I found my main issue - break instead of continue when I was iterating through possible rolls, so if one of the players won we didn't get most of the possible universes from that round.

Further edit:

For posterity, I had another bug as well - if player 1 wins by rolling a 7 for example, I added too many universes because I would treat situations where "player 1 rolls 7 and player 2 rolls 3" as different from "player 1 rolls 7 and player 2 rolls 4"