by R-90-2 » Wed Oct 7, '15, 5:28 pm
Phalanx for the x68000/SNES/GBA had its secret bonus levels, which were notable because some of the powerups were real while others were bonus-zone only enemies that would try to kill you.
The original DOOM had one secret level per episode.
Even more modern games have full secret levels, like how Dark Souls has the Great Hollow and Ash Lake, which are accessed by finding a secret exit to a secret room in Blighttown.
Probably one of the most fiendish secret levels would have to be in Bungie's Marathon Infinity. In the Marathon Trilogy, much of the story and backstory content is delivered through terminals of various relevance. In one terminal on the first level of the game, as well as on one terminal of the last level, the content seems to consist entirely of trash text, but this text is actually hex strings. If you combine the hex strings from the first terminal with the hex strings of the second one in the same text file, and then unzip it twice, it becomes the map file for the secret level, "Hats off to Eight Nineteen".
Do not say: How is it that former times were better than these? For it is not out of wisdom that you ask about this. Ecclesiastes 7:10