well, the card contents are all user-contributed (via the card creation thing), along with the core ‘what cards beat what’.
the main gameplay is trying to work out which of the cards in your hand is most likely to be objectively superior than whatever card your opponent plays - with the aim being to play the one that will end up being objectively superior at the end - and the question of ‘which card is objectively superior’ is, once again, answered by the users. Of course, if an answer to that question hasn’t already been established, it’s supposed to be decided democratically, via ‘finding someone else to convince that your card is the best one’.
I will admit that the version of this game ultimately produced certainly wasn’t the original vision for it. I initially envisioned some sort of room code system, with the game being a 3+ player game where two players would be in a 1v1 with the other players deciding the outcome (a la Quiplash), but with the extra curveball-shaped minefield of precedent thrown in. But, due to a combination of time constraints and having no idea what I’m doing with web dev stuff, I had to nix that and reduce the scope to the mostly-clientside version of Committy you experienced.