Sonic the Hedgehog Pocket Adventure
In August 1999, SNK announced that they were collaborating with Sega to develop a "Sonic the Hedgehog" game for their Neo Geo Pocket Color handheld system. The game was developed by SNK, with supervision from Yuji Naka and Sonic Team at Sega. This marked the first time Sega was directly involved in the development of a "Sonic" game for a non-Sega platform. The team planned for "Sonic Pocket Adventure" to be a return to the classic 2D gameplay style found in the "Sonic" games on the Sega Genesis. In particular, many game design and visual elements are borrowed from "Sonic 2". The game's background music tracks are also 8-bit renditions of music from "Sonic 3". "Sonic Pocket Adventure" was released first in North America on December 4, 1999. SNK released a system bundle with the game included for the holiday season. The game was released in Japan two weeks later, and in Europe in February 2000.
Sonic the Hedgehog 2
For Sonic's 20th anniversary, Sega released "Sonic Generations", which remade aspects of various past games from the franchise. The PlayStation 3, Xbox 360, and PC versions contained a remade "Chemical Plant" level. It also contained a remake of the final boss fight, the Death Egg Robot, as the Classic Era boss of the game. Separately, the Nintendo 3DS version of the game contained a remake of the "Casino Night" level. A "Casino Night" themed pinball minigame was made available for download as a pre-order bonus for the console versions at GameStop. Remade versions of Chemical Plant and Oil Ocean also appear in the 2017 game "Sonic Mania".