The whole lab in one video: picking a track, writing a derivation line by line, reading the ✓/× verdicts, Unstuck hints, the English ⇄ FOL section, and the optional AI tutor.
The checker works fully without any key (✓/×, the reasons, Unstuck). A key adds an AI tutor that knows everything on your board: a plain-English explanation under every step, the Ask box, Explain next step, and AI study notes in the PDF. It uses NVIDIA’s free API under your own account.
Stored only in this browser. Sent to this site’s relay for each question and passed straight to NVIDIA — never saved on the server, never logged.
Export as PDF
A clean study sheet of this derivation: the statements, every step with its rule and the law written out, and the checker’s notes. Your browser’s print window opens — choose Save as PDF.