In the Mario Kart series, players compete in go-kart races, controlling one of a selection of characters from the Mario video game series. One of the features of the series is the use of various power-up items obtained by driving into orbs laid out on the course. These power-ups include mushrooms to give players a speed boost, Koopa Shells to be thrown at opponents, and banana peels that can be laid on the track as hazards. The type of weapon received from an item box is random and often influenced by the player's position in the race.For example, players lagging far behind may receive more powerful items while the leader will only receive small defensive items. This gameplay mechanic–called "rubber banding"– allows other players or computers a realistic chance to catch up to the lead player no matter how far ahead they are. Also in the series, there are special boosts at the start of the race known as a rocket start, which will give racers an early lead when the signal light turns green. This technique upgrades to a Double Dash!! in Mario Kart: Double Dash!!, in which both members of the team use the kart to get a bigger advantage at the start of the race.