RedPen
GitHub

Snap your algebra.
Get it back marked.

RedPen finds the first line where your work breaks and circles it on your own page, like a teacher's red pen. It never writes the answer.

A handwritten notebook page returned with a tick on line 1, a red circle on line 2 and the handwritten note 'distribute to every term'
What comes back: your own page, marked at the first slip.

Try a sample

Sample pages are written with real human pen strokes (Google MathWriting). Their results are replays of a real model run, so they open instantly. Your own photo runs live.

How it decides

  1. Find linesClassical computer vision finds each written line on the photo.
  2. ReadA vision model copies each numbered line exactly — mistakes included.
  3. VerifyA symbolic maths engine (SymPy) checks every line against the one before. The model never decides what is right.
  4. MarkYour photo comes back with ticks, a circle on the first slip and a short hint in handwriting.