site: reviews — Böker Cable Knife, Wyrm Math, Corelle Vitrelle Dinnerware (graduate from finds)

2026-07-11 01:57:30 -04:00
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+---
+name: "Wyrm Math"
+subtitle: "An open-source algebra engine where illegal moves have no square to drop into"
+date: 2026-07-11
+category: learning
+tags: [math, education, open-source]
+link: "https://github.com/dicroce/wyrm_math"
+linkText: "github.com"
+description: "A gesture-based algebra app for iOS and Android built on an MIT-licensed 'conditionally sound' engine — you drag terms across an equation, and invalid moves simply have nowhere to land. Free browser demo; the $4.99 app is how the open-source project sustains itself."
+source: "Hacker News — Show HN"
+fromFind: wyrm-math
+---
+
+![The Wyrm Math interface showing x² − 5x + 6 = 0 with draggable handles under each term and a "Quadratic formula" suggestion pill](./hero.png)
+
+> Drag a term across the equals sign and it either lands or it doesn't — Wyrm Math never lets you commit an illegal algebraic move, because the interface simply has nowhere to put it.
+
+Wyrm Math is built on wyrm-math, an open-source (MIT-licensed) symbolic algebra engine from developer Tony Di Croce, built around one invariant: legal moves are possible, illegal moves are impossible. Equations aren't checked after the fact — they're only ever transformed by rewrite rules, so every state you can reach is sound by construction. That's a different model than the "type an answer, get flagged wrong" tools most algebra software uses: instead of catching the mistake, Wyrm Math makes the mistake impossible to make in the first place.
+
+The mechanism is that the engine enumerates every legal move available for the equation on screen — drag a term across the equals sign, tap an exponent to expand it, pull a shared factor out of two terms — and hands the interface a gesture anchor (a handle and a valid drop target) for each one. There's no illegal target to drop on, so a move you can't legally make just has nowhere to go. Around 25 built-in rules cover linear equations, combining like terms, distribution, fractions, exponent laws, sign-aware inequalities, and quadratics (x² = 9 branches cleanly into x = 3 or x = -3, with both live as navigable states).
+
+"Conditionally sound" is what keeps the engine from being too rigid to be useful: moves that are only valid under a condition — dividing by b requires b ≠ 0 — or that can introduce extraneous solutions — squaring both sides — aren't forbidden outright. Their conditions become visible "Assumptions" that travel alongside the equation through the derivation instead of silently invalidating your work.
+
+The engine is free and MIT-licensed — pure TypeScript, zero dependencies, no DOM, so it can run in a browser, in Node, or inside a native app shell. What actually ships is Wyrm Math, a $4.99 one-time-purchase app confirmed live on both the App Store and Google Play (no subscription, no ads, no tracking), plus a free browser demo at the project's GitHub Pages site if you want to try the dragging before buying. It's a solo/indie project and scopes itself accordingly: coverage tops out around algebra I/II territory rather than a full curriculum, and a "Solution Search" feature visible in the app is still marked beta.