You know, not every game at this year's Gamescom is an international best-seller. Some games are made with a more local audience in mind, and few are as German as this one.
It's called Landwirtschafts-Simulator 3D, and puts you in control of... tractors. Just chugging around a farm. Doing farm stuff. We're not doing much farm stuff here, since we had no idea what we were doing, but from the Germans we saw playing it later, there's farm stuff to do. Ploughing, harvesting, the works.
While this 3DS version is new, the series itself is actually a long-running and mildly successful one on the PC, with an English-language version called Farming Simulator (that you can buy/try on Steam).