Hedgehog Hammer is a sub-game in Sonic Adventure located aboard the Egg Carrier, designed like a traditional whack-a-mole game. This sub-game is exclusive to Amy Rose.
After escaping from the prison room, Amy will come across a room with a single platform surrounded by 8 holes, and jumping onto the platform will start the sub-game. Using her Piko Piko Hammer, Amy must hit the mole-like heads that pop up from the holes and score as many points as she can in the allotted time. Three different types of heads will pop up, each being worth different points:
In Adventure mode, Amy is required to beat Eggman's high score of 2,000 points in order to escape the room, with the Warrior Feather being awarded as a prize for doing so. After the Egg Carrier crashes into the ocean, Amy can return to the room and win the Long Hammer by scoring 3,000 points.
In order to win Emblems in this sub-game, the player must play this sub-game in Trial mode. The first Emblem is awarded by beating the initial high score, and the second one is awarded by beating the previous score. It is recommended to set a low-enough high score to make the second Emblem easier to achieve.