Rotations are easy when its multiples of 90 degrees; 90,180,270,360. Treat them like they’re a complex number like [x+yi]*i=[-y,xi] so rotating by 90 degrees and 180 is i squared [-1]! So [-3,2] rot90 is [-2,-3].
Reflection about the y=x line is change places. [x.y]=[y,x].
So [-2.-3] reflected about the y=x line is [-2.-3]=[-3.-2],
Compile a list of these transform is best practice technique in this area.
