Good coop games on Steam Sale to play with the gf?

The We Were Here series consists of four co-op puzzle games, but I doubt it works with splitscreen. The idea is that the two players are split up into two different areas and have to cooperate to solve the puzzles. So one player will see an image on a wall that corresponds to a code the other player has to put in, that kind of thing. So the whole concept doesn't work for co-op.

Plate Up is probably a little more frantic than what you're looking for but I'll mention it. You're running a restaurant and have to cook and serve food. The gimmick is that it's a roguelike, each day you can buy new items to add to your restaurant. Every three days, you pick a new "card" that changes how your restaurant works; so you can add a new dish, make customers more impatient, that kind of thing.