Basically you can change the color with the letter the color starts with, only the ones in the rainbow except pink (I). Then you change the size with M and L (More/Less), and D puts the pen down and U is up. The change the directions with the arrow keys, and E will erase everything, and lastly space resets the pen to the original page. P.S. In the beginning you have to press S (Slow and detailed) or F (Fast and rigid). You can only change it in the beginning. I think that's it, just experiment in case I missed something.
Hiya peeps! I have a new account, check it out if you want! @PoppleSeeds Thanks to EEKings for the sprite, and a tutorial by someone for actually teaching me pen. Feel free to advertise, and please leave your thoughts in the chat.