KEEN 6

The sixth Commander Keen, from 1992, closes the second trilogy and is the last entry id Software completed under the name. Keen mattered enormously to the company's history. The smooth horizontal scrolling technique John Carmack developed for it was the first demonstration that a PC could compete with consoles at platforming — until then the prevailing assumption was that the hardware simply could not manage it, and the assumption had been reasonable.

What you play is a polished EGA platformer. You run, jump, use a pogo stick for the heights an ordinary jump cannot reach, and carry a ray gun that freezes enemies in place rather than removing them, which turns disabled foes into platforms and hazards of their own. Levels are exploratory mazes rather than left-to-right sprints, rewarding players who check every corner, and the difficulty is judged carefully. The cartoon humour that ran through the series from the beginning is fully intact.

This entry took a different route to market than its siblings, going into conventional retail rather than shareware distribution. In the practice of the time that made a considerable difference — shareware episodes copied freely between friends and bulletin boards reached far more people than boxed software did. As a result, fewer players know this one, despite it being among the most technically and structurally mature things the series produced. For anyone tracing how id Software travelled from platformers to Wolfenstein and Doom, Keen is required reading: this is where the company learned to optimise.