30-Second Flipped Grayscale Expression Warm-Up Sketch

Done as part of a practice session with poses of 30 seconds in length. My current goal is: Improve my understanding of the forces of my facial muscles, in terms of my facial anatomy. This is my latest flipped grayscale multicolor expression warm-up sketch. As you can see, I'm going for my forces and movement of my facial muscles, of my facial anatomy, just to keep my pens and pencils moving. What do ya think?