Welcome to the forum! Making a platform behavior that uses the physics plugin is no easy task, but it can be done with some trial and error (to get the effect you're after). I suggest you experiment with adjusting the example capxs for physics that are bundled with c2; group filtering is achieved by setting enable/disable collisions in the physics behavior. I haven't checked to see if there's a tutorial for using physics to make a platform behavior, but if you're going to use the physics then you need to be fully familiar with how the plugin works (and its limitations) first. If you tag using @ - ie @colludium or whoever then they'll get a notification.