Commander Keen: Invasion of the Vorticons is a PC platformer classic.
Commander Keen: Invasion of the Vorticons game was originally released online as shareware, and did not use the traditional retail model. It consisted of 3 episodes, of which the first was shareware. If you registered, you got the other two episodes. Supposedly, below was what Apogee sent you in the mail when you registered – a disk, and an instructions/hint sheet. I can’t confirm that as I believe I downloaded the 2nd and 3rd episodes back in the day.
This game was followed by: Commander Keen: Keen Dreams; Commander Keen in Goodbye, Galaxy!; and Commander Keen in Aliens Ate My Baby Sitter! In 2001, a game titled Commander Keen was released for the Gameboy Color, which was the final release in the series.
If you haven’t played it, Commander Keen is a great platform game designed by Tom Hall and powered by id Software tech, back when the IBM PC was thought to be too slow to do good platform games. You play a kid genius who assembles a “bean with bacon megarocket” out of tin cans and blasts off into space to fight the evil Vorticons. It used to be underrated, but appears to have found the notoriety it so richly deserves.
There apparently was a packaged release of this at some point, perhaps a later repackaging, but I don’t have it. If this one really came direct from Apogee, it’s hard for me to treat it as any less than completely legit, but that doesn’t mean I wouldn’t pick up a packaged copy if it came my way.