Ready to run project is in ReadyProgram folder.

Demonstration at:

https://www.youtube.com/watch?v=qKFfr3srl_w

Description:

There are 7 different materials: air, stone, water, sand, smoke, acid and indestructable, floating variant of stone.

Brush can have 1-20 size(pixels) and has a shape of a rectangle.

You can select materials and increment/decrement brush size by clicking with left mouse.

You can place particles on the canvas by clicking/holding left mouse.

Screen size is 1024x768 and simulation is done with a grid of rectangles 4x4.