As someone who has 4 copies of the game(one for my big, and little bro, grandma and me), as play multi-cart play all the time, here is how it works: CO-OP: all 4-players are placed in the same room, and are required to complete the area in a set time limit with everyone having linked HP, so if P1 takes damage, P2, P3, and P4 take damage, and that goes for everyone, their objective is to get to the final room and kill the boss, everyone does damage to the same boss. VERSUS: 4-players are put on the same floor, sometimes same room sometimes different, and are forced to go around and kill enemies, which will spawn more in the room they died in until 3 of the players die and leave one standing, unless all of them make it too the boss and kill the boss on their ends, causing a TIE! (Enemies will not spawn in the room where they are killed for another player unless the player leaves and comes back.)