Hey, When writing games in other (imperative) languages, I like to separate the game logic from the rendering. For this I use something similar to the observer pattern. With rendering I mean anything only related to how objects are drawn to the screen. Animation state for example. On my journey of exploring game programming with haskell (and FRP), I wonder what a good way of archiving something similar would be. If the rendering has no internal state, one can just write a function draw :: GameLogicState -> IO () But when the rendering of an object has an internal state (e.g. animation frame) than this is not possible. Now I could write a Wire/Signal (whatever FRP implementation I use) that translates to a RenderingState: render :: Signal GameLogicState RenderingState draw :: RenderingState -> IO () which is fine, except when my game is made of many objects. Than I need to associate the state of one object in GameLogicState with a sub-signal in render. That could be done by giving every object an ID and letting GameLogicState contain a map from IDs to ObjectLogicState. I fear that when I really have a lot of objects, assembling and decomposing the map could become a major bottleneck. So I am wondering: Is there (or can someone think of) a different pattern by which this could be archived? Or asked different: How would you do it? Thanks! Nathan