I found a new way to create a filled square with pen! How this works is it starts with a high pen size in the centre of the square, then works its way to the corners, changing its pen size by -1 for every pixel it moves. This is repeated for each corner to create a square! Since the pen is drawing over itself multiple times, the transparency starts to become less defined, which is why it only looks transparent with the transparency set to 99. Also, it's only slow because I deliberately didn't make the custom blocks run without refresh, just to show you how it works.
