The animal on the cover of AngularJS is a thornback cowfish (Ostraciidae). This fish of many names—thornback, thornback cow, backspine cowfish, shortspined cowfish, blue-spotted cowfish—is usually found on rocky reefs or sandy slopes in a tangle of sponge and weeds in the Western Indo-Pacific region. They feed primarily on worms and other invertebrates.
These boxfish can grow up to 15 centimeters long and anywhere between 3 to 50 centimeters wide. Members of the boxfish family are recognizable by the hexagonal pattern on their skin. Their bodies are shaped like a boxy triangle from which their fins, tail, eyes, and mouth protrude, allowing them to swim with a rowing motion. As they age, their shapes change from more rounded to more square-shaped, and their brighter colors dim.
The thornback cowfish protects itself by secreting cationic surfactants through their skin, which is triggered by stress. The toxins, usually secreted in the form of a mucus, dissolve into the environment and irritate fish in the surrounding area.
The cover image is from Johnson’s Natural History. The cover font is Adobe ITC Garamond. The text font is Adobe Minion Pro; the heading font is Adobe Myriad Condensed; and the code font is Dalton Maag’s Ubuntu Mono.