∇ Z←Face mirror Z [1] ⍝ [2] ⍝⍝ mirror Z horizontally (Face=2 or 5), vertically (Face=1) or not at all. [3] ⍝ [4] →(Face=3 4 6 1)/0 0 0,1+↑⎕LC ◊ Z←⌽Z ◊ →0 [5] Z←⊖Z ∇