Commander Keen in Invasion of the Vorticons is a three-part episodic side-scrolling platform video game developed by Ideas from the Deep (a precursor to id Software) and published by Apogee Software in 1990 for MS-DOS. It is the first set of episodes of the Commander Keen series. The game follows the titular Commander Keen, an eight-year-old child genius, as he retrieves the stolen parts of his spaceship from the cities of Mars, prevents a recently arrived alien mothership from destroying landmarks on Earth, and hunts down the leader of the aliens, the Grand Intellect, on the alien home planet. The three episodes feature Keen running, jumping, and shooting through various levels while opposed by aliens, robots, and other hazards.
In September 1990, John Carmack, while working at programming studio Softdisk, developed a way to implement side-scrolling video games on personal computers (PCs), which at the time was the province of dedicated home video game consoles. Carmack and his coworkers John Romero and Tom Hall, along with Jay Wilbur and Lane Roathe, developed a demo of a PC version of Super Mario Bros. 3, but failed to convince Nintendo to invest in a PC port of their game. Soon afterwards, however, they were approached by Scott Miller of Apogee Software to develop an original game to be published through the Apogee shareware model. Hall designed the three-part game, John Carmack and Romero programmed it, Wilbur managed the team, and artist Adrian Carmack helped later in development. The team worked continuously for almost three months on the game, working late into the night at the office at Softdisk and taking their work computers to John Carmack's home to continue developing it.
Released by Apogee on December 14, 1990, the trilogy of episodes was an immediate success; Apogee, whose monthly sales had been around US$7,000, made US$30,000 on Commander Keen alone in the first two weeks and US$60,000 per month by June, while the first royalty check convinced the development team, then known as Ideas from the Deep, to quit their jobs at Softdisk. The team founded id Software shortly thereafter and went on to produce another four episodes of the Commander Keen series over the next year. The trilogy was lauded by reviewers due to the graphical achievement and humorous style, and id Software went on to develop other successful games, including Wolfenstein 3D (1992) and Doom (1993). The Vorticons trilogy has been released as part of several collections by id and Apogee since its first release, and has been sold for modern computers through Steam since 2007.
Gameplay
The three episodes of Commander Keen in Invasion of the Vorticons make up one side-scrolling platform video game: most of the game features the player-controlled Commander Keen viewed from the side while moving on a two-dimensional plane. Keen can move left and right and can jump; after finding a pogo stick in the first episode, he can also bounce continuously and jump higher than he can normally with the correct timing. The levels are composed of platforms on which Keen can stand, and some platforms allow Keen to jump up through them from below. The second episode introduces moving platforms as well as switches that extend bridges over gaps in the floor. Once entered, the only way to exit a level is to reach the end, and the player cannot save and return to the middle of a level. In between levels, Keen travels on a two-dimensional map, viewed from above; from the map the player can enter levels by moving Keen to the entrance or save their progress in the game. Some levels are optional and can be bypassed, while others are secret and can only be reached by following specific procedures.
Each of the three episodes contain a different set of enemies in their levels, which Keen must kill or avoid. The first episode includes Martians, the second largely uses robots, and the third more species of aliens. All three episodes also include Vorticons, large blue canine-like aliens. Levels can also include hazards like electricity or spikes. Touching a hazard or most enemies causes Keen to lose a life, and the game is ended if all of Keen's lives are lost. After finding a raygun in the first episode, Keen can shoot at enemies using ammunition found throughout the game; different enemies take differing numbers of shots to kill, or in some cases are immune. Some enemies can also be stunned if they are jumped on, such as the one-eyed Yorps, which block Keen's path but do not harm him. Keen can find food items throughout the levels which grant points, with an extra life awarded every 20,000 points. There are also colored keycards that grant access to locked parts of levels, and in the third episode on rare occasions an ankh, which gives Keen temporary invulnerability.
Plot
The game is broken up into three episodes: "Marooned on Mars", "The Earth Explodes", and "Keen Must Die!". In the first episode, eight-year-old child genius Billy Blaze builds a spaceship and puts on his older brother's football helmet to become Commander Keen. One night while his parents are out of the house, he flies to Mars to explore, but while away from the ship the Vorticons steal four vital components and hide them in Martian cities. Keen journeys through Martian cities and outposts to find the components, despite the efforts of Martians and robots to stop him. After securing the final component, which is guarded by a Vorticon, Keen returns to Earth—discovering a Vorticon mothership in orbit—and beats his parents home, who discover that he now has a pet Yorp.
In the second episode, the Vorticon mothership has locked its X-14 Tantalus Ray cannons on eight of Earth's landmarks, and Keen journeys to the ship to find and deactivate each of the cannons. Keen does so by fighting more varied enemies and hazards and a Vorticon at each cannon's control. At the end of the episode, he discovers that the Vorticons are being mind-controlled by the mysterious Grand Intellect, who is actually behind the attack on Earth.
In the third episode, Keen journeys to the Vorticon homeworld of Vorticon VI to find the Grand Intellect. He travels through Vorticon cities and outposts to gain access to the Grand Intellect's lair, fighting mostly against the Vorticons themselves. Upon reaching the lair, he discovers that the Grand Intellect is actually his school rival Mortimer McMire, whose IQ is "a single point higher" than Keen's. Keen defeats Mortimer and his "Mangling Machine" and frees the Vorticons; the Vorticon king and "the other Vorticons you haven't slaughtered" then award him a medal for saving them.
