Coderetreat is a structured activity designed to help software developers practice improving their skills on the fundamentals of application engineering and testing.

The activity is a facilitated event of a small group of developer participants. The basic structure is something like this:

• Find a partner to pair-program with
• For 45 minutes, attempt to use TDD to implement Conway's Game of Life simulation
• When time's up, delete your code
• Have a brief retrospective as a group
• Find another pair and attempt the problem again (often with a constraint added by the facilitator)

For more information on the Game of Life, check out it's Wikipedia page.