Game controllers, with some exceptions, have mostly standardized around a certain form-factor: two analog sticks, four face buttons in a diamond shape, four shoulder buttons, Start, Select, and a directional pad. But of course that hasn’t always been the case - analog sticks weren’t standard until the Playstation 2 came out in 2000, and shoulder buttons were introduced with the Super Nintendo in 1990, which also added more face buttons than systems had had before.
But the real basis for the modern controller, if you ask me, is the original Nintendo Entertainment System. The controller was simple by modern standards, with only a few buttons, but its main innovation was the directional pad, usually just called the D-pad. This is the cross-shaped pad on the left side of the controller used for selecting different directions. Before this, most directional input on video games was done with joysticks, which were tall and required larger movements to trigger. In contrast, the D-pad made the controller smaller and more accurate. You could hold the controller in your hand and just use both your thumbs to control it, instead of having to hold the base of the joystick, or have it braced on a table to use.
Nintendo’s engineer Gunpei Yokoi originally designed the D-Pad for use in a handheld Donkey Kong game in 1982, replacing the individual directional buttons used on earlier handhelds. It proved so popular that there has hardly been a video game system without a D-Pad since.
Now, the D-Pad isn’t just for video games. Nearly every DVD and Blu-Ray player has a D-Pad of some sort or another, most smartphones had them until touchscreens became ubiquitous, and even a lot of cars now have D-Pads on their steering wheels. And even though most games are primarily controlled through analog sticks now, you’ll still see a D-Pad on every Xbox or Playstation controller.