I have around 100 to 200 particles in my game. Then I have 5 to 20 regions (circle-shape) which should count the particles which enter them and add some force to them, so they change their direction.
My idea was now to keep a list of all particles and every region should check the whole list every frame, whether a particle is inside it. For this I calculate the distance between the particle and the central point of the region and check weather its <= the radius of the region.
Is this the most efficient way to do it? Or should every particle have a list of all regions and check whether they are in one of it? Or a totally different approach?
I would like this application to be able to run also on older mobile devices like an iPhone 4S.