Activating this trainer:

Press F1 at main menu.

Listen for 'Trainer Activated'.

Press desired hotkey. All hotkeys can be changed on the trainer.

Trainer Options:

NumPad1: God Mode

NumPad2: Unlimited Lives

NumPad3: Add Bomb

NumPad4: Freeze Timer

NumPad5: End Timer

NumPad6: Change Score By 500

NumPad7: Kill All Enemies

NumPad8: Activate Gatling Mode

NumPad9: Unlock Hard Mode

NumPad0: Unlock All Colors

NumPad/: Unlock Retro Sound

Notes:

Kill All Enemies: Press hotkey to kill all enemies on the screen (including boss enemies).

Unlock Hard Mode / Colors / Retro Sound: On main menu press hotkey to unlock stuff.