Contour

Contour is a geometric topology thinking training tool designed for students, working professionals, and those who want to practice focused thinking during spare moments, all interested in geometry and graphical reasoning. Features include: real-time generation of an unlimited number of one-stroke drawings (no pre-set levels); branching point filtering to avoid mindless drawing; automatic completion of straight lines (you only need to select at the forks); undoable errors with concise text feedback; and a daily challenge for easy comparison of time and records. The fun lies in predicting which path will lead to a dead end and how to minimize backtracking, rather than scoring or leaderboards. It features a Bauhaus-style hard-edged color block interface and has no login, ads, or in-app purchases.