Logo & the turtle

Logo is a programming language created in 1967 at BBN by Wally Feurzeig, Cynthia Solomon, and Seymour Papert, designed from the start for children. Its most famous feature is the turtle: first a robot that crawled across paper trailing a pen, later a triangle on a screen.

You program the turtle with commands it understands from a first-person point of view — FORWARD 100, RIGHT 90, REPEAT 4 [FORWARD 100 RIGHT 90]. Because you can imagine being the turtle, geometry becomes something you do with your body before you do it with algebra. Papert called this body-syntonic reasoning.

Logo descends from Lisp and inherits its list processing and clean recursion — which is how a child drawing a spiral quietly meets one of the deepest ideas in computing. The modern descendants you've probably met include Scratch and the turtle module in Python.