Tamagotchi by Namco.
Why are these touchscreen-tickling titles familiar, you ask? Three of the four have been proving their mettle on other mobile platforms. GeoDefense Swarm and Tamagotchi are currently available in the iOS App Store; Age of Zombies is available in both the Android Market and iOS App Store; and Bullet Asylum has been in the works for some time -- we were treated to a video preview last summer, which you'll find below. No word yet on release dates, but the foursome's mere presence on Microsoft's site makes us think that we won't have to wait all that long before initiating the download sequence.