@maxoakland they were working within very tight constraints, I think it's amazing how much people have been able to wring out of the 64. And, I suspect one could come up with alternatives...I mean flipping bytes isn't computationally intensive, so you could do it yourself on the CPU, but I guess it'd need copies since the VIC is reading sprite memory directly, so you can't update it in place, at least not without glitches (I'm guessing, I have no idea what I'm talking about).