Make it so that when particles fall off the screen that they appear on the opposite side that they fell off of.
Example 1: Some sand falls off the bottom side of the screen. It appears on the top of the screen and continues to fall.
Example 2: You use a fan to push some sand off the right side of the screen. The sand appears on the left side of the screen.
If your not sure what I mean go to http://dan-ball.jp/en/javagame/dust/ Use erase tool to erase the walls on all of the sides of the screen. Then press the thing that says SIDE-OFF until it says SIDE-LOOP. Put some sand or another particle in the level and that's what I mean.
This would be a new button on the menu that would toggle between the way it is now and the looping thing.
It would mess up a lot of saves, but it is a cool idea, so there should be an option to turn looping on/off... Actually, gol particles already loop, so it is possible.
I like the fact that in Dan-Ball's Powder Game, the water is made of particles while the walls are like Powder Toy's walls, and plus it would make all liquids more realistic.