Complex sentence: The game's first demo build was released on February 7,2011, and development continued until December 1,2015, when the mod's development team announced it would cease further development of "Project M".
Split into simpler sentences: The game's first demo build was released on February 7,2011, and development lasted until December 1,2015. On December 1,2015, the mod's development team announced it would cease further development of "Project M".