Clash of Clans is an online multiplayer game in which players form communities called clans, train troops, and attack other players to earn resources. There are four currencies or resources in the game.[3] Gold and elixir can be used to build and upgrade defenses and traps that protect the player's village from other players' attacks and to build and upgrade buildings. Elixir and dark elixir are also used to train and upgrade troops and spells. Gems are the premium currency.[3] Attacks are rated on a three-star scale and have a maximum timed length of three minutes.[3]