State Weaver

State Weaver is a simple, hands-on editor for finite state machines. You place states on a canvas, mark one as the start, draw arrows between them, and label each arrow with the input symbol that triggers it. Then you hand the machine a sequence of inputs and run it — the currently active state lights up and the machine steps from one state to the next along whichever transition matches each symbol, so an abstract diagram becomes something you can actually watch execute.

It's meant to make the idea click rather than to be an exhaustive tool: build a machine that accepts strings ending in a certain pattern, mark accepting states, feed in a test string, and see at the end whether the machine landed in an accepting state or not. Stepping through one input at a time makes it easy to follow exactly why a machine accepts or rejects, and a small set of example machines gives you something to explore and tweak before building your own from scratch.

The app is a focused multi-screen tool — a canvas editor for laying out states and transitions, a run panel for feeding input and watching it step through, and a small library of saved machines stored locally on the device. No account, no ads, no connection needed; everything you build stays on your phone.