Zarfdog: Total noob here, but while playing Alien Breed (not Tower Assault) I search and search, but eventually i run out of keys and I get trapped and can't progress. Am I missing something? Or do I have to get lucky and open the perfect set of doors? Or is there another trick of which I'm not aware?

I am really digging the old school vibe of the DOS version, but I'm frustrated that I can't even get to level 2! Any help is appreciated. Thanks in advance.

Bolch76: Yes, in this game you CAN run out of keys and get stuck. There are many dead-ends and locked rooms which don't contain any worthwhile item. The game strongly encourages you to play the levels multiple times and find the optimal route.
Also, I stronlgy advise you to buy a map at an Intex terminal as soon as you can afford it.

Bolch76: Intex terminals are blue screen-like things, you can find one on level 1 near the beginning in a little alcove, as soon as you go through the two locked hangar doors. Approach it and press "Backspace" to activate.

Zarfdog: This has helped me a LOT! The game is pretty cool, actually, and this has helped enjoy it even more. This is why I love GOG, for people like you. Thanks again!

Blakes7: I don't get why the backspace key wasn't mentioned in the manual. It is a very important key to know to progress through the game. Not sure how to enter a level code either even when using the intex terminal.