Diagnose. Find the flaw in someone else's proof.
A tutor that explains everything is a tutor that prevents you from thinking. This one does the opposite: it presents you with proofs that are almost right — proofs that look correct, sound plausible, and end at the intended conclusion — but that quietly cheat at one specific step. Your job is to find the step, name the rule it violates, and explain how a real proof would have made the move legally.
Not a chatbot
You are not asking the tutor to explain. You are diagnosing its work. The asymmetry matters: you are the active agent.
Errors are designed
Every flaw maps to a real, named failure mode — petitio principii, anachronistic dependency, unjustified existence, eyeball-equality, wrong common notion.
Wrong looks right
The figures and proofs are deliberately convincing. If they did not feel correct, the exercise would be useless — and so would the muscle it builds.
Five near-cases.
Canonical diagnosis
The rule that was violated