Properly spelled D/Generation, this was an early puzzle/arcade PC Video Game published by Mindscape in 1991.
The story is: it is The Future, some guy named Derrida down at the Genoq corporation ordered a very important package, and you're the delivery guy. You arrive with your Jet Pack on the 80th floor just to discover that the building's security system has turned on its inhabitants, and the building is flooded with biological weapons through the ventilation system. There are four kinds of them, called the A/Generation, B/Generation, C/Generation, and D/Generation, each more powerful and dangerous than the last. Your task: get the package to Derrida, while rescuing survivors and sealing all the air vents. And all you get to do it is a laser gun and a laser-gun proof suit. When you finally think you've gotten the package to Derrida, things take a sudden turn for the surreal.
Need more example tropes for this game.