The Atari 2600 was designed, almost exclusively, to play Combat. It has the ability to animate only 3 sprites: player 1, player 2 and "ball". There are many hacks to get around this, but we're talking about the pre-release period of the Atari Video Computer System, AKA VCS, the Atari 2600.
The only other game in mind for the system was Pong, which actually come out for the system in the form of Video Olympics, and it was created by one of the 2600's TIA chip designers, Joe Decuir. That chip literally synced up the processor with the television's refresh rate, and had each scan line drawn out of processing exactly when the electron beam was moving over the proper position on screen. The 2600 has no frame buffer. Essentially, when it's in the CPU, it's drawn on the screen. The machine only had 1024 bits, not bytes, of RAM.
But that's neither here nor there. For more info on the fascinating hardware that was the Atari 2600, read Racing the Beam by Ian Bogost and Nick Montefort. https://mitpress.mit.edu/books/racing-beam
Video Olympics could be considered to be the 100-in-1 of Pong games, with dozens of variants on the Pong theme. Combat takes the same sort of approach, with lots of game modes, but the actual gameplay was based on another arcade game. Rather than just recreating the arcade game, however, Combat expands on the theme, as Video Olympics did.
Combat is, to my mind, the only game on the 2600 that really holds up to this day. It's still fun, despite it's graphical limitations. For its day, it was the Super Mario Brothers of the Atari: that cart you could always turn to for fun.
It's elegant in its simplicity, extremely deep in its variations on a theme, and even offers a few asymmetrical playing options: one player can be given a different set of planes from the other.
Combat is the Go of computer games. Oh, and all the graphics are drawn in 1's and 0's. Same for the numbers on screen: big binary sprite maps. Here, look! http://benfry.com/distellamap/150dpi/combat-illus-150dpi.png