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.