Walk around the caverns and collect the 10 letters in the word 'INVINCIBLE' in that order. Each letter picked up leads to a breakout sub-game. Once all letters are collected, a door opens in the first screen. Walk through it to exit the caverns and win the game.
Translation: "Congratulations! Hereby you've become The Invincible! Back Space".
Once in-game, enter the following in emulator monitor: G 2E50