Again, limited time to get anything done tonight, but I decided to plough ahead anyway and tackle the Mask mode (if you recall, the Mask mode is similar to Deluxe Paint stencils, allowing you to "lock" tiles to prevent them being drawn over).
I'd already created the necessary cursor graphics a couple of days ago, so I started off by displaying the current tileset, overlaid with the mask information (essentially, you left-click a tile you want to add to the mask, and right-click to remove it - tiles affected by the mask are highlighted by a special "X" shaped cursor).
This was fairly painless to implement, and so I delved into the Pen mode function and added the code to make the Mask actually take effect. Despite the code only taking a matter of 10 minutes to add, the tool is both amazingly powerful and immensely useful. Time was my enemy (I hate having to cut my code time short, particularly when I'm on a roll), so tomorrow's first task is to apply the mask to all of the other drawing tools.
