By way of IGN Microsoft has announced Halo: Spartan Strike for "Windows devices and Steam PC", a followup to the top-down twin-stick shooter Halo: Spartan Assault.
The new title is due as soon as December 12th 2014, and you can find out a little more in a 9 minute gameplay video with commentary from 343 Industries producer Fred LaPorte. Somewhat oddly, there's no word on whether the game will show up on Xbox platforms, but then, the original took a while to make its way over as well.