Once you acquire the ship, get in the ship and hold one finger in the touch screen (not on the directional pad). Tap elsewhere on the screen 23 times to begin the classic 15 puzzle game, which you can play for prizes.
Secret area
Area
How to unlock
Earthgift Shrine
Defeat Lich in the Cavern of Earth.
Hellfire Chasm
Defeat Marilith in the Mount Gulg.
Labyrinth of Time
Defeat Lich, Marilith, Kraken, and Tiamat. Visit Chaos Shrine to unlock.