Bubble Bobble Revolution Cheats

To access the final ten levels, you have to collect 9 letters. To get these, kill at least 4 enemies in one Super Bubble, and collect the key icon that is dropped. Then, carry on until the boss of that zone (levels ending in 0) and kill it. Instead of dropping a giant gem, it will leave a letter. Pick up nine of these (one per boss) to ultimately finish the game.