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The Sega Saturn had among its many fine titles 'Virtual On,' a fighting game with giant robots and a unique control mechanism. Two four-way joysticks each with a trigger and a thumb button were referred to as Twin Sticks, and this controller was made available in a home version. As with all non-standard game controllers, the Twin Sticks didn't sell as well as the manufacturer intended, and so Sega took a bath on the cost.
However, unlike other custom controllers the Twin Sticks are completely compatible with all other Saturn games that permit digital control. That's because Sega thoughtfully used the same double-74153 encoder chip for both the Twin Sticks and the standard controller. Saturn software is unable to distinguish which type of controller is connected. So applying the principles of custom controller construction you've learned by reading the rest of the