For five years I coached First Lego League teams. These were 5th - 8th grade kids who were interested in Lego robots, but sometimes had a hard time sitting still, or focusing on tasks for extended periods of time. For three months, teams of up to 10 kids would work on a building a Lego robot to do the FLL challenge tasks, put together a science project based on the challenge theme, and generally work to assemble themselves into a functioning team. It's a lot to ask from kids, but in addition to what they learned, I'd reward their hard work with a pizza party at the end of the season.
I started gathering brain teasers, both as a way to break up sessions of intense work, and as a fun thing to during the pizza party. After five years, I had accumulated pages and pages of riddles and brain teasers. They were great puzzles, and I wanted to share the collection with others.