D/Generation HD

D/Generation operates from an isometric point of view consisting of a series of floors, each dotted with various maze-like rooms. The aim of the game is to get through each room, eliminating hostile bioweapon creatures, avoiding or disabling security measures, and rescuing as many trapped people in the area. During the first floor, the player will acquire a laser gun that holds unlimited ammunition and which can be used to kill bioweapons and trigger switches; it also possesses the ability to bounce off walls and use teleporters. Alongside the main weapon, the player can also find a limited number of grenades, bombs and other gadgets that can help in dealing with security measures and bioweapons.

On each floor, the player's aim is to reach a gravity lift that will take them to the next floor, with the exception of the final floor, and must navigate a maze of interconnected rooms. Each room features a mixture of doors, security measures, and, in most cases, bioweapons. To get through a room, the player must navigate through doors triggered by switches, watch out for security measures (such as turrets and mobile laser fences), and deal with any hostile bioweapons in the room; in some cases, having to eliminate all and sealing any open air duct vents on the wall, in order to proceed further. On most floors, some doors will not open without finding a security key to unlock them.

D/Generation's takes place in an alternate future in which greater advancements of technology in the 20th century culminated in a nuclear war in Asia that led the United Nations (UN) to ban the research and creation of atomic and biological weapons. In June 2021, a courier (the player) receives a job to deliver an emergency package from Paris to a biomedical research facility in Singapore, owned by bio-research company Genoq, at the request of its top researcher, Dr. Jean-Paul Derrida. Upon arriving on the 80th floor of the facility's skyscraper, the courier finds the building in a state of chaos following a major accident, and encounters a survivor who reveals that the building's upper levels are swarming with bioweapons.

Determined to find Derrida, the courier works to make their way through each floor, rescuing as many people as possible, while dealing with security measures and three classes of bioweapons: A/Generation, a red blob that can absorb its target; B/Generation, blue cylindrical column that can merge into the floor and crush its target; and C/Generation, capable of resembling humans and objects in order to ambush its targets. Along the way, the courier learns more about the situation, and discovers that Genoq secretly was conducting illegal bioweapon projects without the UN's knowledge, using its work in biomedicines to cover up its research. Eventually the courier meets a survivor who has learned Genoq intends to bomb the building to cover up the disaster, knowing the truth would ruin the company.

D/Generation was originally developed for the 128K Apple IIe (utilizing Double-Hi-Res mode) under the name D-Generation. An early preliminary version for that platform exists and is dated 1989. According to the Prince of Persia journals by Jordan Mechner, the game was completed in 1990 but the MS-DOS version from 1991 appears to be the first public release. While the original Apple II version was fully playable and well polished, it was never completed nor publicly released.

Electronic Gaming Monthly gave the Amiga CD32 version a 7.25 out of 10. They criticized that the Amiga CD32 controller does not work well with the game's isometric perspective, but praised the combination of action and puzzles, describing the game as both addictive and challenging.

In 1994, PC Gamer US named D/Generation the 32nd best computer game ever. The editors wrote that its "clever mix of puzzle-solving and arcade action hooked nearly everyone who did get a chance to try it out". That same year, PC Gamer UK named it the 44th best computer game of all time, calling it the "best game of its type on the PC". In 1998, PC Gamer US declared it the 38th best computer game ever released, and the editors wrote that its "gameplay is still as fresh and inviting as the day it was first released".