: Not as many as you think! Marathon didn't have much of a technological edge
: over Doom, which was released first; the most glaring feature is the
: ability to look up and down. ;) At any rate it was not the first game to
: have texture-mapped polygons by far. Even Bungie's own Pathways Into
: Darkness did that before M1.
: If you gave Marathon credit for the first to have secondary fire on every
: gun, though, I don't think anyone could argue with you. ;)
FWIW Whatever You Please employed a modern map-making technique of having the end and the beginning of the level very near to each other, seperated only by a height difference. Not to mention the multiple, semi-intertwined pathways you can use to complete the level.
The M2 engine did manage to incorporate ambient sound into levels. I can't remember for sure whether or not this was ground-breaking, but something tells me that it was.