Thanks for playing! Right now the prestige points are based on gold earned in total, but in the next patch I reworked it a bit and made it a bit more clear how to earn prestige points.
With the graphics: yeah on web in general it is a bit more laggy, but I also tried to improve it with the next patch. I think it comes mostly of the various sprites. I tried to compress them now, which should improve performance, but you must tell me in the end if it runs better or not :D