use of undefined type

I'm developing a tool that will help game programmers to develop games in Haskell. To create a game object, the programmer must call the function *object* as follows: object name_of_object position_of_object speed_of_object I would like also to add another param to this function, which type would be anyone defined by the programmer. Unfortunately, as Haskell does not allow things like: type Game = (Name,Position,Speed,t) where t is an undefined type, I'm forced to add "t" to the left side of the type synonym (type Game t = ...). But this is realling doing a mess in my code, since I have to pass this "t" all around. That's why I ask if anyone knows another idea to solve this problem... Thanks a lot, -- Andre W