* layer where it should be drawn and a texture.
* The coordinate system used here is a virtual one. It would be a bad idea to
* populate whole levels with particles. So we're using a virtual rectangle
* layer where it should be drawn and a texture.
* The coordinate system used here is a virtual one. It would be a bad idea to
* populate whole levels with particles. So we're using a virtual rectangle
* (virtual_width, virtual_height). We're using modulo on the particle
* coordinates, so when a particle leaves left, it'll reenter at the right
* side.
* (virtual_width, virtual_height). We're using modulo on the particle
* coordinates, so when a particle leaves left, it'll reenter at the right
* side.