Demo - Automaton (experimental)

Watch an automaton read a word

This automaton decides whether a binary number is divisible by 3. Its state is the remainder so far: reading a bit doubles the number and adds the bit. It is declared once with fromGraph, then both run and drawn. Type a word and the walk grows as you type; edit it and the playhead stays at the same position. Below, you play the automaton yourself: each answer is a choice, a wrong one takes a detour, and changing an earlier answer cuts off the old future.

Now you be the automaton

Same word. At each bit, pick the state the automaton moves to. Scrub back to an earlier question and pick differently: everything after it is replayed from your new answer. The link in the address bar holds the word and your answers, so it replays this exact walk.