Game devs looking to enhance "engagement" (read: monetization) for their mobile titles now have an ally in Amazon. The Bezos-backed company has just made plug-ins available free to Kindle Fire developers using the popular Unity game engine. Now those devs will have access to APIs for In-Game purchasing and GameCircle which, in the latter case, allows for the addition of Achievements, as well as the ability to Whispersync across devices. So, what does this mean for you, the
