Sound Test
At the title screen, highlight Options, hold Up (now highlighting Start) and press Start. The sound test is a bit confusing to use since there is no text. Press Up/Down to toggle between Music (upper) and SFX (lower), press Left/Right to choose a track, and press Start to play it.
Alternate Ending
On Level 9, When the stage's sole enemy appears press DOWN and you will enter a secret tunnel. Blast the incubator and the computer to view a different ending.
Passwords
Effect Password
Bird Mode (press A, B, and Select to deactivate/activate bird mode) DLVTRKBBRD
Easy Level 02 DVYLWKVYDG
Easy Level 03 GRYLWKWVYC
Easy Level 04 DRYLSRWVYL
Easy Level 05 GVZLSRSQYY
Easy Level 06 DVZLBVSQYZ
Easy Level 07 GRZLBVBQYY
Easy Level 08 DRZLBVBQYZ
Easy Level 09 GVYNBVBQPK
Infinite Energy DLVTRKBNRG
Infinite Lives DLVTRKBLVS
Level Skip (press A, B, and Select then left or right) DLVTRKBLVL
Unlimited Ammo DLVTRKBWPS
Medium Difficulty Passwords
Effect Password
Level 2 QVYLWKVYYC
Level 3 TRYLWKWVYY
Level 4 QRYLSRWVPT
Level 5 TRZLSRSQPS
Level 6 QVZLBVSQVN
Level 7 TRZLBVBQVL
Level 8 QRZLBVBQVN
Level 9 TVYNBVBQQD
Hard Difficulty Passwords
Effect Password
Level 2 DLTLWKVYYC
Level 3 GNYLWKWVPP
Level 4 DNYLSRWVPT
Level 5 GLZLSRSVPW
Level 6 DLZLBVSVVB
Level 7 GNZLBVBQVL
Level 8 DNZLBVBQVN
Level 9 GLYNBVBQQD
Graphics: Rubén Ángel Gómez, Sergio Palacios, Julio Moruno
Music, Sound: Alberto José González Pedraza
Design: Rubén Ángel Gómez
QA Manager: Carol Caracciolo
Producer: Michael Archer
QA Supervisors: Jeff Rosa, Dale Taylor, Brian Regan, Matthew Canonico
QA Lead Analysts: Jim Craddock, Mike Patterson
Project Leads: Jeremy Pope, Jennifer Walka
Game Testers: Jordi J. Galcerán, César Gilabert, Alberto Moreno