This is a fantastic simulation! My high-school students in Hong Kong LOVE it for its mad behaviour when you change the parameters violently and I love it because it makes the relationship of kinetic theory to the Gas Laws so clear.
Would it be difficult to modify it so that one can control the volume also and, preferably, have a temperature control rather than a velocity control? This would make it more accessible to the students. Ideally, I would like four controls corresponding to p, V, n and T with radio buttons to select which one is going to be controlled by the student and which one is allowed to vary as a result of that change.