Sonic Lost World is a 2013 action-adventure platform game developed by Sonic Team. It is part of the Sonic the Hedgehog series, and was released in October 2013 for the Wii U and Nintendo 3DS in PAL regions by Nintendo and by Sega in North America and Japan. A port for Microsoft Windows was later released in November 2015. Lost World focuses on the efforts of Sonic the Hedgehog to stop the Deadly Six, an alien tribe that serves as the game's main antagonists, as they seek to siphon energy from the Lost Hex, the game's setting. Sonic and his long-time sidekick Tails must team up with Doctor Eggman, normally their enemy, to stop the Deadly Six, leading to conflicts among the three parties. While the gameplay is typical of the Sonic series in some ways, it adds parkour mechanics and features largely cylindrical level design with an emphasis on alternate pathways. The game also features the Wisp creatures from Sonic Colors as power-ups. The game began development shortly after the 2010 release of Sonic Colors. It was designed to be streamlined and fluid in movement and design, using tube-like level design and a simple, bright color scheme. The game received mixed reviews upon release; its controls and the Deadly Six were frequently criticized, but its visuals and audio were seen positively. Downloadable content was released both alongside and after the game's release, adding features such as additional levels and a new type of Wisp power.