[colin9876]

Try this, even with all the interface taken out the physics engine goes painfully slow after > 30 grains of sand! Just tap the mouse to add sand!
Proves we need the SDL.dll

So if its not done on colours - how does it do it? I doubt that there is an array storing the properties of every pixel. Can you have to substances Exactly the same colour that do different things? Remember (100,100,100) doesnt look much different than (108,100,100) etc but it would be enough to recognise it as a different element