He created LambdaMOO during his 13-1/2 years as a member of the research staff at Xerox PARC, from 1983 to 1996, where he worked in the areas of programming language design and implementation, programming environments, and online collaboration systems. Curtis left Xerox in 1997 to become a principal architect and co-founder of PlaceWare, a web-conferencing company that was acquired by Microsoft in 2003. Outside of work, Curtis is now the sole proprietor of Pavel's Puzzles (http://www.pavelspuzzles.com), a website selling mechanical puzzles, mostly designed by him.