Press the green flag. Move the mouse around. Move the slider around.
I wondered how this would look with more particles, but that was impossible with clones because of the 300 clone limit. So, I did away with the clones all together and stored all the data in lists. Now you can have as many particles as you like, it'll just get laggy if you have too much. I also made the particles point directly away from the mouse when they spawn. I made the radius vary, and the color vary based on the radius. The pen size increases relative to the distance from the mouse pointer. Particles are deleted if they touch the edge, get too far away from the mouse pointer, or if there are more particles than are allowed by the variable. Also, a huge round of applause to alistic, as he came up with the awesome fundamental concept.