Completing Batman: Arkam Asylum was bittersweet, as Rocksteady really delivered on their promise of the best Batman game ever, but thankfully there’s reason to keep exploring the island even after the credits roll. The easter eggs. From Harvey Dent’s half-ravaged cell to  Ra’s Al Ghul’s toe-tagged body,  the game is filled with winks to fans of the comic, no surprise considering it was penned by the writer behind Batman: The Animated Series.

“There are surprises around every turn,” said writer Paul Dini in an interview with USA Today’s Game Hunters. “That is the magic of playing the game. You can play the game straight through and ignore all that and then you can go back on another go-round and just look for surprises, Easter eggs and hidden clues. In some cases, you have to be as good a detective as Batman is in order to move onto certain levels because there are some forensics for you to unravel at certain points.”

Though the Joker is getting all the attention in the game’s marketing materials, the Riddler proves an equally worthy foe for the world’s greatest detective. With more than 240 challenges scattered about the asylum’s grounds, it’s the game within the game. One that I’m more than happy to play.