Irrational Games' 'Insider' page on their website reveals a bunch of features that ended up being cut from BioShock.

Among these, the most significant feature to get the axe was an entire pressure system that required you to adjust the atmospheric pressure for each room, switching the setting between low, medium or high.

The system would have visually changed every area depending on the pressure, with added fog, light and rendering effects. It would have also altered the behaviour of enemies, reducing a Splicer's perception in low pressure rooms, for instance.

Irrational chose to get rid of the pressure mechanic as it would have tripled the amount of work for the art team and made it impossible to control the mood for each room.

“Most importantly — and this is the issue that put the nail in the system’s coffin — was that we never found a good way to clearly convey the effect of pressure through audiovisual changes," states BioShock's Technical Director Chris Kline.

Turns out the code was solid though, because portions of it were used to create the fog and lighting effects in the Arcadia section, where you have to kill off the trees.

There were also going to be little men operating the machinery behind those Pipe-Mania style mini-games, the idea being that you're connecting the pipes to feed Adam to the mutated creatures trapped inside the contraption. Now that's just plain weird.

We've also learnt that an insect-based ecology and helpful Nav-Bot to aid you in getting around Rapture were also considered for inclusion in BioShock, but ultimately binned.

We have to say, we'd particularly like to see the little machine gremlins make an appearance in BioShock 2. Pretty please?

Be sure to check out the list in full on Irrational's site.