So, you assign a value to that state, and then you solve the depth limited subgame using those values at the leaf nodes. It turns out that this does not work in imperfect-information games. I can give you a really simple example of why. This is a game that I called Rock-Paper-Scissors+, is exactly like rock-paper-scissors, except if either player throws, what is it? Scissors? Yes. If other player throws scissors, then the winner gets two points, and the loser loses two points. That's just to break the symmetry of the game.