I'm pretty much a total beginner with 6502 assembly.
After watching David M's Planet X3 series, I was puzzled by his tile editor. In particular, with the feature to rotate the tile horizontally and vertically (essentially, is behaves like a torus). I've been playing around with writing a routine to do just that. Horizontal rotation is the easy part, we traverse an 8-byte array and use ROR and ROL for each byte, something like:
I can get a similar behavior for vertical rotation. Conceptually, I get it. Y = $1000, $1000 = $1001, $1001 = $1002, ... , $1007 = Y. But what's an efficient way to implement this?