Game Closure is a startup that helps game developers in building HTML5-based games. Recently, they turned down acquisition offers from both Facebook and Zynga, which would be a risky move. Of course, Game Closure was also raising $12 million dollars at the time, which they are announcing today. The investment was led by Highland Capital Partners, with participation from SV Angel, Yuri Milner, Joi Ito, Charles River Ventures, Benchmark Capital, Greylock Partners, and General Catalyst Partners.