"Cheer the [F = ma] up!" — Newton's second law stepping in where the swear word should be, with an arrow pointing up because force has a direction. A wholesome physics pun. For Newton fans, secondary-school physics teachers, anyone who has been told to perk up by someone who could really stand to learn what a vector is. Vector design (literally), monochrome and bold. Looks just as good on the back of a hoodie as it does on the front of a t-shirt.