Trips to Ikea typically take the crown as the best way to test the strength of a relationship. We know, however, that a day shopping for Swedish furniture has nothing on the crucible of friendship that is Mario Kart. The adorable racing game brings out the brutal competitor in everyone. This week, Nintendo dropped Mario Kart Tour onto iOS, which means mobile users can now red shell all of their relationships into smoking heaps of rubble from the convenience of their smartphones. The game hasn't received the glowing reception you might expect off the bat thanks to some initial server issues that prevented some players (including me) from racing, and the fact that unlocking the full breadth of game features will require a $5 monthly subscription fee.