ColProof-M is a tool for students to learn to accomplish a geometrical proof. The students can add propositions to their proof per Drag & Drop and choose reasons for a proposition. An interactive illustration implemented with Cinderella helps to follow the reasons. According to the didactic Design Pattern FEEDBACK ON DEMAND the students are able to let ColProof-M check their solution for mistakes automatically. If they don’t know how to go on with their solution the students can get hints, like it’s written in the Pattern HINT ON DEMAND.