"Euclid's 'Elements' Redux" is an open textbook on mathematical logic and geometry for use in grades 7-12 and in undergraduate college courses on proof writing. It is a new edition of the most successful textbook of all time, "The Elements", compiled by Euclid around 300 BC. It contains several hundred exercises as well as a partial answer key. Although it is a copyrighted work, it is licensed under the Creative Commons Attribution-ShareAlike 4.0 International License. Download it for free at: http://starrhorse.com/euclid/