The N64 controller featured a novel — and ultimately unique — three-pronged design. The idea was to put the right type of input — directional pad or analog stick — under your thumb at the right time, although this wasn’t immediately obvious to all first-time users. You’d hold either the leftmost or center prong in your left hand, and your right hand always held the rightmost prong. When you were using the analog stick, you’d naturally find your index finger positioned over a trigger button, often used for primary actions. With your right hand, you had easy access to the other action buttons (B and A) as well as four C buttons, often used to control the virtual camera in 3D games. The top edge of the controller had a shoulder button on either side, although these tended to be used less often than in prior systems.
In addition to its distinct layout, the N64 controller had something else up its sleeve: an expansion slot of its own. Each of the four controllers plugged into the N64 could hold a proprietary expansion device of one sort or another, something unlike any of the other consoles of its generation. Subsequent consoles such as the Dreamcast and Xbox would explore this idea further, but no other console from Nintendo leaned on the idea as much as the N64.
Several different “paks” were released over the course of the console’s lifetime, adding support for saving game data (the Controller Pak), force feedback (the Rumble Pak), and even interoperability with Game Boy and Game Boy Color games (the Transfer Pak).