Use arrow keys to move your pen, use the plus and the minus sign to make your pen bigger. The pen will start 3 seconds after start. HAVE FUN!
this came from my own mind. I used the pen add-on to make this project. After growing past 25 (pen size), the scratch Cat will lock to 100% (normal sprite size). (This also works when going past -12!) To go to mouse pointer, hold the A key and move your mouse!