Many weapons contain slots for the insertion of "upgrade cores"; depending on the core, upgrades can affect a weapon's rate of fire, clip size, damage, or other mechanics. Random items and loot, such as new (and more powerful) weapons and upgrade cores, drop at random intervals and when enemies are defeated. The class of a drop differs by rarity, ranging from "stock" to "legendary" class. Unwanted items can be converted into metal, which is then used to re-roll a weapon's statistics. Aiming is accomplished by targeting a blue laser in the direction a player wishes to shoot. Players can "dash and melee", knocking down many enemies at once to give themselves more space. When a player accumulates enough experience, they "level up" and can spend points on three active and three passive abilities, chosen from several options on a trio of skill trees. Each ability has a cooldown timer, requiring players to use them strategically. Points may be switched from one skill tree to another at any time. When a player dies, their experience multiplier is reset. When Alienation story mode is completed, the player unlocks missions with bounty-like assignments and quests with special items as rewards. The player unlocks more difficult enemies, more powerful weapons, and the ability to complete difficult, procedurally-generated, levels set in the alien's space craft. Two types of "keys" are unlocked at the end of the game. UFO keys are used for "loot runs", and ark keys are used for player-vs-player fights. Development and release Alienation was developed by Finnish video game company Housemarque and published by Sony Interactive Entertainment. It was released on April 26, 2016 exclusively for the PlayStation 4. The game, first hinted at in January 2014, was announced at the 2014 Sony Gamescom conference. In a question-and-answer article on the PlayStation Blog in April 2014, Mikael Haveri of Housemarque said that they are inspired for many of their games by other games. Haveri cited Dark Souls and Demon's Souls as examples, saying that they "take a concept [the developers] like and try and improve it or put a twist on it". According to Haveri, Alienation would have content (such as better explosion mechanics) which players had not seen before. He noted the chance of references to other Housemarque games, similar to how the incorporation of Resogun ships into Dead Nation. In April 2015 the developers released details about Alienation gameplay, saying