use a webcam and color tracking to use a piece of paper (cut to your preferred size) and something like a colored sharpie with the cap on or a pencil with a colored tip. ive found posca markers work great. make sure to choose a color that stands out. follow setup instructions once you start it, and it should work! Keep in mind this tool is pretty bad for accuracy, and you shouldnt use it in place of a tablet. rather, its more of a fun toy and can be used to confuse your friends.

EDIT: this is the link that works now im pretty sure

https://drive.google.com/file/d/1zWD4ItHX3aNkUQ_GU4rRAxcdQg-oAsad/view?usp=sharing