Hmm, Gaussian elimination over GF(2). Let's go! ...Some time later... This is quite hard! I think thinking about this puzzle as Gaussian elimination is not he

Hmm, Gaussian elimination over GF(2). Let's go! ...Some time later... This is quite hard! I think thinking about this puzzle as Gaussian elimination is not helpful! I think the controls would work better if you dragged the row/column onto the one want to change.