Okay, this is an idea I have had based on the powder game, which is similar to this. It would be an element called:
BALL
What it is is a small ball, that can roll and bounce.
HOWEVER: It is not a 'moving solid'. This is because you would be able to set it's ctype and it would take on the colours an properties of that element, including powders. For example a ball with ACID ctype would be pink and would slowly eat through whatever it touches. A URAN ball would gain heat under pressure. A GRAV ball would float around. Some elements, like life and stkm, cannot be set as the ctype.
I think this would be great for many things, like cannons, and machines, like slot machines.
You could make rollercoasters and stuff.
Lastly, stkm should be able to 'connect' to it and roll around in it, like Zorbing balls.
Even if you think this is stupid, and you don't like, please do not hate.
It is not a moving solid, in the sense that it can represent liquids and powders, even gases. It simply represents whatever element it is in a compacted bouncy form.
*Sigh* That is the game I got the idea from... I prefer powdertoy because it is way cooler and has more features.
I knew you got the idea from that game, that's why I posted that.
Still, it wouldn't be as nasty to code as moving solids would it?
Oh, I thought it would be easier. This idea is dead then?