How to Draw on Any Website
This extension lets you draw on any website you're on, picking the line color and thickness, and then taking a screenshot of what you've drawn. You can also draw freehand, holding Shift as you click to make a straight, Circle, Rectangle, or line with a thickness of your choosing. Once you're done drawing, you can see what you've done and how you've done it, so you can adjust and improve your skills.
When you take a screenshot, you can see the area you've drawn on, so you can adjust your drawing to fit that area. You can also use manipulate its thickness to make your drawing more or less visible.