This is a boilded down version of my Serum system (example). It's a 2D particle system and there's no GLSL involved! Feel free to play around and be inspired. Always credit me when sharing results. Non-commercial use only, contact me otherwise.
In this tutorial we create a component which can detect when objects are on top of each other (colliding). This works for any 2D input with alpha. You could also render a 3D scene and use it there, it just works on the u v axis though.