void Entity::InfInfCollisionResponse(Entity &a, const Ray &na, Entity &b) {
// If both elements are standing still or both are moving, move them away
// from each other. Otherwise, move the moving one.
void Entity::InfInfCollisionResponse(Entity &a, const Ray &na, Entity &b) {
// If both elements are standing still or both are moving, move them away
// from each other. Otherwise, move the moving one.