[originally from svn r9801]
<li>each row and column contains the same number of black and white
squares.</ul>
<p>
-Left-click in an empty square to turn it black it out, or right-click
-to turn it white. Click again in an already-filled square to cycle it
-between black and white and empty; middle-click to reset any square to
-empty.
+Left-click in an empty square to turn it black, or right-click to turn
+it white. Click again in an already-filled square to cycle it between
+black and white and empty; middle-click to reset any square to empty.