Prey was originally going to let players fly through Talos 1

We recently spoke with Prey lead system designer Seth Shain about the Gloo Cannon, the "amorphous semi-solid fluid-firing" weapon that enables players to freeze enemies and, more importantly, build platforms that enable access to locations on the Talos 1 space station that would otherwise be out of reach. Its presence in the game made life interesting for the artists, Shain said: They "hate it because they want every square inch of the station to be beautiful, and if the player can get somewhere high up, then they feel they need to make it look good." That's an understandable frustration. But it could've been worse. 

"There was another power that we cut because we just couldn't make it work or make it fun, it didn't hit our quality bar. It was a power that would directly allow you to fly around the space [station]," he explained. "That one just amplified that problem. [The artists] were really happy when they cut that, you're mostly constrained to the walls with the Gloo gun." 

Free flight is a tricky business for any game, and this isn't the first Bethesda game it's been cut from. Players could levitate and fly in Morrowind (and you actually had to, in order to reach some areas), but the power was removed from subsequent Elder Scrolls games because of changes in the way the games handle interior and exterior spaces. That wouldn't have been an issue in Prey, since you're stuck inside a space station, but it's interesting that even under those more favorable conditions Arkane decided that it just wasn't working the way it wanted.   

Shain also revealed in the interview that the weapon was originally called the Goo Gun, but as it evolved and changed during the game's development the team decided, "Let's just put an 'L' in there and then it's the Gloo Cannon." And thus was history made. Read the whole thing right here.