Wyrm Math is a gesture-based algebra app for iOS and Android (with a browser demo) built on an open-source engine the author calls “conditionally sound” — instead of letting you make a move and then flagging the error, the interface simply won’t let an invalid step land. You drag terms across the equation, and if a move would break the algebra, there’s nowhere to drop it. The result is a workspace where the usual trial-and-error of solving equations gets replaced by a constrained set of moves that are always legal.