You Win!
I played this for far to long, over an hour. Tried mapping the area out which helped some but I think it just made me spend more time in the long run. If you get to the giant tanks you are basically on the way to winning the game so keep at it. I am afraid players will stop playing before uncovering the better upgrades.
Since there is so unforgiving steps, it might be a valid option to just give the player a mini map.
Some bugs, the game stutters a lot at first movement but not after that. If you die at a position where you can use oxygen tank you can still use it after you suffocate but then you are locked there. Same with dying in general, there is a lot of reloading the page due to this.
Nice entry, and the one I've spent the most time in so far.