Why I built Rex: a whiteboard with a tutor on it

Chatbots made answers free. That broke studying, not fixed it.

The problem I kept seeing

A student pastes a problem into a chatbot. They read the answer. They nod. By morning it is gone. I watched this for months before I built anything. The answer was never the hard part. The hard part is the step where your own thinking breaks. Nothing in a chat window looks for that step. It just hands you the next answer.

What Rex is

Rex is a study whiteboard for iPhone, iPad and Mac. You put a subject on an infinite board: notes, PDFs, your own handwriting, interactive charts, 3D science scenes. A tutor walks the material with you, out loud.

The tutor has one rule: it does not hand you answers. It asks you to try a step first. It finds the step where your attempt went wrong. Then it makes you redo that step. Like a good human tutor, it cares about your thinking, not your answer.

The parts students actually keep using

• Boards that become flashcards. Anything on a board can become a deck. The schedule is spaced repetition. Exam week? It becomes a quiz.
• The Rexer. A board becomes a narrated lecture. Two hosts, your notes, recall questions in the gaps. Your commute becomes revision.
• A solver that shows its working. Exact algebra and calculus, line by line, on your device. It works with no connection.
• Voice, on device. Talk through a problem hands-free. Your speech never leaves the phone.
• A chart library. Sixty-plus interactive widgets. Build them, publish them, remix them.

Try a chart without installing anything

A few of them now run in your browser. Watch what a 3×3 matrix does to space. Build a cross product step by step. Or drill Russian cases with the Case Compass. No account. No install. :)

Free to start

Every tool is on every plan. The free plan is a real plan, not a trial. A generous daily tutor allowance. No card. No timer. Paid plans add capacity. They never lock features. No ads. No tracking.

Rex is on the App Store: Rex: Study Smarter.