Microsoft used its press conference at this year’s E3 gaming expo to show off the gaming capabilities of the HoloLens, its augmented-reality headset. The HoloLens is essentially a head-mounted PC running Windows 10: Its combination of sensors, spatial-sound projection, and a front lens work together to overlay holograms on the surrounding environment. In terms of early apps, Microsoft has shown off a Mars simulator, a 3-D modeling application, and now, at E3, a new version of Minecraft, the popular world-building game. Although the Minecraft demonstration audibly impressed the E3 audience, some pundits have raised questions about the HoloLens’ narrow field of view, and how that could affect not only the development of apps, or the device’s marketing as a whole. Check out the latest augmented reality jobs. In any case, it’s increasingly clear why Microsoft paid $2.5 billion for Mojang Studios, the developer behind Minecraft: It needed a killer app for its revolutionary new technology. The fact that the game continues to generate tons of revenue on traditional gaming platforms almost certainly contributed to the decision. But for the third-party developers who’ll be needed to transform the HoloLens into a hit, the emphasis on 3-D Minecraft raises an interesting question: Is this hardware primarily a gaming platform, a productivity platform, or—like the old-fashioned PC—some combination of both? If Microsoft emphasizes the HoloLens’ gaming aspects, the device will end up in direct competition with Oculus Rift and other VR headsets scheduled to arrive on the market over the next year. If it chooses instead to market the headset as a productivity tool, it’ll end up competing against PCs, tablets, smartphones, and pretty much every other device capable of sending an email or displaying a schedule (not to mention playing games). That conundrum may compel certain developers to take a “wait and see” attitude toward the technology. But others may be tempted to plunge in anyway—in which case, they may want to read up on all the new factors that will come into play when building HoloLens apps.