War Machine

Type "PLINKERTYPLONKERTY" on the title screen (in caps) and then press the Space bar
This will enable the cheat mode and will allow you to use the cursor keys 
to jump to the adjacent rooms. 
Also, if you press F10 it takes you to the final battle with the Alien Queen.

Typing "GOODBYEBACKDROPS" followed by enter 
will kill the backdrop graphics for a more 8-bit feel.