...the greyscale looks really cool...

That's monochrome :p

Thanks though.

Builderboy should write a tutorial on physics for calc games.

I thought he did already?

He might have, and I just missed it.

I kinda did, but the physics for this sand wouldn't be covered in it, as it is just pseudo-physics, a simple algorithm that really has no basis in real fluid dynamics

Do you have a link to your physics tutorial? Would you be willing to write one for fluid dynamics?

Here is the link: Note its not completely finished I really should start writing some more lessons

http://ourl.ca/4279/79303

As for the fluid dynamics, of course it isn't completely far away from realistic physics, it isn't exactly very realistic either.  Pressure is ignored completely, as is illustrated in the diagram below.  In real world physics, the water line would be even, but the physics I implemented would leave the water at levels similar to the diagram.  Then again, while it may not be realistic when it comes into the actual equations and things like viscosity and pressure, it does present a very nice and quick method for on calc simulation There might even be some other sets of rules that are equally simple and result in better fluid movement.

On the subject of physics, I just had an idea for physics for sand in your game.  Here would be the rules, with lower rule numbers being higher priority:
1) If block below is empty, move down
2) If block below is fluid, swap fluid and this block
3) If block to the right/left and down is empty, move to that position

Maybe instead of a fluid dynamics, I could write about the power of pixel based physics for simulating large physical elements

Some just were

Lost the entire physics engine to some sort of data corruption. It was in need of a complete overhaul anyway.