BlackBerry 10 is still months and months away, but the first devices are nearly finished and the time to build apps is now — and to that end, RIM has just informed developers that the new operating system will target two screen resolutions. We'd previously heard that RIM is building just two types of BlackBerry 10 device to start, and today we know how many pixels they'll use. While the very first device will have a 1280 x 768 screen, a la the BlackBerry 10 Dev Alpha, subsequent phones will differ. Full touchscreen devices will have a 1280 x 720 resolution (aka 720p, the popular 16:9 aspect ratio), and devices with the traditional portrait QWERTY keyboard will also have a traditional square screen at 720 x 720. If you've built apps for 1280 x 768 already, RIM suggests you letterbox at that resolution, removing the top and bottom 24 rows of pixels, or simply adjust for each resolution individually. Considering that we're now expecting up to six BlackBerry 10 devices, developers will be happy to know what to do to keep those apps compatible.