Use the mouse to trace your reflection in your computer's monitor - but you won't be able to actually view your drawing until you press enter. If you think you've done well enough, or awfully enough, you can save it as a .BMP file.
This game automatically adjusts to the current size of your monitor, but is set to work on displays that are a maximum of 3840 x 2160 - wow! It's possible to play on a screen resolution higher than that (and congratulations on your incredible wealth if you do) but you'll be stuck drawing in a 3840 x 2160 box in the top left corner.
Just a funny idea I had a week ago, possibly while scrolling through Netflix. The idea of tracing your reflection or drawing something that you can't actually see until you're finished isn't new, but I think trying to make out your features in your monitor and having to use your mouse to draw brings something different to the table. It can really test your depth perception and memory (especially if you move out of place!).
I realize you could get the same effect and produce a more accurate pic by creating a black screen in a program like Paint and then using a white brush, but to let you in on a little secret I don't think accurate portraits are what make this a fun idea to me.
Source is included, in case hundreds of years into the future someone needs to adjust the maximum drawing area. You'll need Multimedia Fusion 2/Clickteam Fusion 2.5 to open it.
An example of what kind of results you may expect is uploaded as an attachment!