Load up a game in single player and see if any levels have arrows over them- if so, replay those levels. Also make sure you have all three relics (compass, wheel, telescope). If not, replay the necessary level to obtain the relic. If you were missing any relics, be sure to play the Dock and Pirate Ship levels. Then fight the Wizard again, but play through Wizard Castle Interior level and go into the final door (skipping the first three doors) rather than going to the Final Battle level. If all this is done, you should get credit for properly beating the game.
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