Show HN: Penmentor – Claude marks up your handwritten math like a teacher

A maths mentor at the tip of your pen. Press a key during you activity by hand: Claude, Gemini or GPT marks your activity on the
screen akin a instructor alongside coloured pens, gives you hints alternatively of answers, and shows the idea as a 3Blue1Brown-style animation.

_{Handwriting in xournal++ → one key → the stumble is marked on the leaf → box the integral → an interactive manim animation. (video; for a repeatable record the pen is scripted and the model's answer is a fixed example.)}

I study calculus alongside a pen tablet in xournal++. I kept screenshotting my activity into Claude and study lengthy answers back, whenever what I wanted was a instructor looking complete my shoulder: circle the mistake, tick what's right, nudge me toward the next step, and show me why. penmentor is that, one key away, on my own Claude subscription.

• Hints, not answers. A ladder from a nudge to naming the method to a faint shade of the next line: you do the thinking, which is what makes it stick.
• Feedback on your own work. The archetypal genuine error circled anywhere you made it, accurate lines ticked, afterward lines that inherit the error underlined. The marks remain during you keep writing; Esc clears them.
• Practice that makes you recall. Questions on your key steps (answer by typing or by writing), find-the-error drills, "which method fits?".
• See it. Box what you desire to comprehend and get an interactive animation made alongside 3Blue1Brown's own manim: drag the bounds, retype a value, observe Riemann sums near in.
• Whole leaf aware. A small xournal++ plugin shares the leaf you are on, not fair what fits on screen.

penmentor runs on the AI command-line delegate you already use, on that subscription. Pick the example in Settings; its prefix says which delegate answers:

Settings lists the agents you have installed. How all one is run and what it sees: the guide.

git copy https://github.com/AbdullahAlhariri/penmentor ~/src/penmentor ~/src/penmentor/bin/penmentor --selftest

Linux on X11 (best alongside i3), alongside one of those agents logged in (claude, codex or agy), affirmative rofi, slop, xdotool and PyQt6. Bind bin/penmentor to a key (example). Setup, keys and how it works: the guide.

MIT