When Microsoft started taking pre-orders for its HoloLens developer headset, it teased a digital storytelling app named Actiongram. But what is it, exactly, and how does it work? The folks in Redmond are finally ready to explain. In a detailed blog post, Microsoft has revealed that Actiongram is all about letting you create short, effects-laden mixed-reality videos without having to know a thing about 3D graphics. You just have to pick characters and props, place them in the world, and tell your tale. It's not particularly elaborate, but it shows how augmented reality apps can simplify this kind of creativity -- a video that would take days of compositing work could be wrapped up in an afternoon.