I tried to buy Armor III and it disappeared off the list without taking any money, but without installing either. Now I can't buy it, and I think I'll need it..
The Crux is a great example of idiocy in level design. Half the time I can't get OUT of the air room after finishing it, which is really just crap considering how hard the room itself is.
You don't take damage from barrels. Plant them inside explosions and you can run around as effectively a bomb, slaughtering everything as long as you have a supply of barrels..