Mounting a door sweep on the front of your robot like
http://www.homedepot.com/p/Frost-Kin...SB36/202525375 should let you push around litter and still clear the scoring platforms
Edit: Mcmaster has brush strips in up to 10 inch heights but 3 inches should be plenty
http://www.mcmaster.com/#74405t4/=vwsld9