Yeah, it's definitely worth noting that the Japanese spend a much greater amount of time away from home than you probably see in any other country. A heavy public transportation system, incredibly-dense population centers, 6-day school week, near-slavish work hours...definitely a fertile ground for handheld dominance. In fact, you could probably argue that the Japanese are just so damn tired when they get home from all this walking, working, studying, and subway riding that casual games at home just fit the situation better. It's still not a great sign to see a game like this sell so spectacularly when others fail when Nintendo (corporate) only gives a damn about the Japanese market.