It's cel-shaded graphics. In video games, this is used to both give a game a more fantasy/otherworldly feeling as well as help present visual information in a more easily recognizable style. For example, it helps you notice your bike coming at you from far off sooner and helps makes enemy shapes more distinct. This can most obviously be seen in games like Borderlands and the most recent Legend of Zelda.
Very cool and unique. Just don't understand how this game takes place in a post-apocalyptic scenario some how has perfectly working super advanced hoverbikes. Cool none-the-less.
