RYNO Motors' single-wheeled electric scooter is self-balancing, has a turning radius of zero when stopped, & only takes up about as much space as a folding bicycle -- so it's conceivable that commuters could bring one onto a train.
Except for the rings of Saturn, the Ring Nebula is probably the most famous celestial band. via NASA (photo: Credit: Composite Image Data - Subaru Telescope (NAOJ), Hubble Legacy Archive; Processing and additional imaging - Robert Gendler)
Drawing of a mouth - side view - draw a straight line to see the angle/slant nose to chin; also look for negative space to get the form of the mouth. So helpful because I want to learn how to draw faces from the side as well as I do from the front!