+You can also use the cursor keys to move around the grid squares and
+lines. Pressing the return key when over a grid line will draw or
+clear its edge, as above. Pressing the return key when over a dot will
+pick up an arrow, to be dropped the nest time the return key is
+pressed; this can also be used to move existing arrows around, removing
+them by dropping them on a dot or another arrow.
+