Nightmare mode - Successfully complete the game on the Hard difficulty to unlock Nightmare difficulty. In Nightmare mode, any enemy that is destroyed will shoot a blue ring in your direction.
Play as Plissken (lizard) - Successfully complete the game on the Normal difficulty to unlock Plissken (lizard).
Play as Tsugu-Min (robot) - Successfully complete the game on the Easy difficulty to unlock Tsugu-Min (robot).
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