Doom II

Doom II was not dramatically different from its predecessor. There were no major technological developments, graphical improvements, or substantial gameplay changes. Instead, the development team took advantage of advances in computer hardware since the release of the original game that allowed them to do more with their game engine by making much larger and more intricate levels. The game still consists of the player navigating large nonlinear levels.

Each level is infested with demons that can be killed with a variety of weapons that can be picked up throughout the game. Levels are completed by finding an exit, whether it be a switch or a teleporter; the goal is simply to advance to the next area. As with its predecessor, Doom II's levels can be completed in a straightforward fashion. However, because the levels are nonlinear, players can wander off the beaten path, and those who do are often rewarded with bonuses like health pickups and more powerful weapons.

Immediately following the events in Doom, the player once again assumes the role of Doomguy. After defeating the Spider Mastermind, the marine finds a portal to Earth opened by demons. After returning to Earth, the marine finds that it has also been invaded by the demons, who have killed billions of people.

The humans who survived the attack have developed a plan to build massive spaceships which will carry the remaining survivors into space. Unfortunately, Earth's only ground spaceport has been taken over by the demons, who placed a barrier over it, preventing any ships from leaving. The marine battles hordes of demons and is able to deactivate the force field, allowing the remaining humans to escape. Once all the survivors have escaped Earth, the marine is the only human left on the planet.

Most of the levels were designed by Sandy Petersen, with American McGee playing a significant role as well.

The final level, Icon of Sin, contains an easter egg where two of the artists put the severed head of John Romero as the sprite hidden behind the icon on the wall which must be damaged by rocket splash damage three times to win the game. Romero, while playing the level to work on its sound effects, accidentally stumbled upon this in-joke of himself. After realising what his co-workers had done, Romero himself answered by recording his voice saying "To win the game, you must kill me, John Romero", putting it through various filters to distort it, then reverse the recording to create the "demonic chant" spoken by the head upon spotting the player. The photo that was scanned for the "John Romero's head"-sprite was from a Businessweek photo shot in 1994.

The reception of Doom II was positive, with reviewers saying it refined everything that made the original Doom good. The game was reviewed in 1995 in Dragon #216 by David "Zeb" Cook in the "Eye of the Monitor" column, who stated that, "if mindless but intense carnage is what you want, you'll get your money's worth. It's just not a must-have, keep-on-the-hard-drive-forever game. If you need to have more Doom, get this."

Writer/game designer Chris Crawford used the level "Barrels O' Fun" to illustrate a point about death in video games, explaining he chose the level as his example because it is "one of the most complex and sophisticated challenges in one of the very best games of the 1990s".

In 2022, John Romero created a new level called "One Humanity" for the game to raise money for the Ukrainian Red Cross, and the United Nations Central Emergency Response Fund following the outbreak of the 2022 Russian invasion of Ukraine. By March 2022, the new level had raised more than $29,000.