Penmentor - AI math mentor that marks up your handwritten work
Show HN: Penmentor – Claude marks up your handwritten math like a teacher
Penmentor turns your pen tablet into a personal math tutor. While you work by hand in xournal++, press a key and Claude, Gemini, or GPT reviews your page like a teacher with colored pens — circling the first real mistake, ticking correct lines, and underlining steps that inherit an error. Instead of handing over answers, it climbs a hint ladder from a nudge to naming the technique to a faint ghost of the next line. Box any expression and get an interactive 3Blue1Brown-style manim animation you can tweak. It runs on your existing Claude Code, Codex, or Antigravity subscription and is open source under MIT.
What I wanted was a teacher looking over my shoulder: circle the mistake, tick what's right, nudge me toward the next step, and show me why.