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Ludum Dare is a 48 and 72 hour game making competition globally hosted twice a year publicly on the internet for anyone to participate. The 48 hour version is strictly for solo participants, while the 72 hour version is relaxed bit with more time and no restraints on team size and source code usage.

The 48 and 72 hour game jam: http://ludumdare.com/compo/. Theme: Shapeshift