User talk:Ptrah x

Hello, I'm David Eppstein. I wanted to let you know that I undid one or more of your recent contributions to Tesseract because it did not appear constructive. If you would like to experiment, please use the sandbox. If you think I made a mistake, or if you have any questions, you can leave me a message on my talk page. Thanks. —David Eppstein (talk) 05:27, 17 July 2015 (UTC)