Tandem control

Each player controls 3 paddles moving in tandem in FoozPong.

Tandem control is a video game control mechanic where two or more characters are tied to a single input causing them all to move in the same manner. This was common in early sports video games before it was possible for the hardware to handle separate AIs for all the non-human-controlled teammates. Tandem control has similarities to follow behavior.

History

Shortly after Pong was released, four-player variants, like Pong Doubles, were made which featured two paddles on either side, each controlled by a human player. One could conceive of increasing the number of players to six with three paddles on either side or even more, but trying to crowd even four people in front of a small cabinet was uncomfortable, it wasn't practical to try and fit any more. Being limited to only one on-screen character per player greatly restricted the creativity of game designers and made sports games with a realistic number of players unworkable. Four tennis players would be cramped, but doable, but 22 soccer players would be impossible.

Today, developers would simply assign an artificial intelligence to each non-human-controlled character, but this wasn't possible at the time. AIs did exist, and some were even complex enough to defeat amateur players at chess and checkers, but they were also extremely slow and resource intensive, so there would be no way a fast-action game could handle multiple AI-controlled characters. So, game designers needed a different approach if they wanted to solve this problem.

No doubt there were plenty of instances of Pong Doubles being played in four-player mode by only two humans, with each player manipulating both dials on their side of the cabinet to control both paddles. However, anyone who has ever tried this know that it's surprisingly difficult to control two completely independent on-screen paddles while also tracking a ball. This would become exponentially more difficult as additional dials were added, not to mention that each dial requires an additional appendage.

Game designers eventually realized that, while controlling two paddles independently with two dials is quite difficult, controlling two paddles in tandem with a single dial is much easier. In fact, they figured this out pretty quickly; Super Soccer has each player controlling three on-screen paddles which move in tandem, and it came out only a year after Pong. With this new control mechanic, game developers were able to give the illusion of entire teams of players all working in harmony, all from a single player's input.

While tandem controls are still used occasionally in games, once it became possible for a player's teammates to be controlled with AI, most games switched away from tandem control. By the late 1980s, very few games were still using the mechanic, and, those that were, were coming up with unique ways of handling it, like the horizontal inverse tandem controls used in Binary Land.

Usage

Tandem control appears to have been born out of the desire to have a team of characters on the screen while still only requiring a single player to control them all, and, at this, it's quite effective. When comparing a game which supports both tandem and single character controls like Home Run, most players tend to favor the multiple characters from the tandem control. Tandem controls do take some getting used to however.

Implementing tandem control starts out fairly simple, but can become more complex. An easy way to think of tandem control is to picture one character as the "real" character which is controlled by the player, and all the others as "clones." Since the game will already have routines for displaying the player's character at a specific location on the screen, adding more characters is usually as simple as calling the routine multiple times with each clone being drawn offset from the real character with a constant x and y coordinate offset. Adding collision detection isn't much harder, you just have to add a collider to each clone and adjust it's position as well. If the characters can attack, the programmer needs to perform the attack for each one, whether that be swinging a sword or firing a projectile.

whose position on the screen is fixed to the real character by applying This forces them to always be in lockstep with the real character. Collision detection with projectiles is typically applied to these characters, and, depending on how the game implements wall collision, they may or may not be affected. For example, in the game Volleyball!, the six-player team moves in tandem, and, if any one player were to go out of bounds, all players are prevented from moving. However, in the FoozPong game mode of Video Olympics, when a paddle would be forced up off the screen, it simply wraps around to the bottom of the screen.

Although tandem control was largely forgotten in sports games once CPUs became powerful enough to use AI for the other characters, it continued to see use in a variety of different genres. Various scrolling shooters include support ships which fly in tandem with the player's ship like with Galaga and Tiger-Heli, and it also shows up with interesting variants in puzzle video games like with Binary Land and Baba Is You, and strategy games like Bokosuka Wars.

Examples

Screenshot	Title	Notes
	Avalanche	With a single dial, the player moves all of their shields in tandem.
	Binary Land	This game takes a unique approach to the mechanic. The player still uses only one controller which moves one penguin as expected, but the left and right directions for the second penguin are inverted.
	Bokosuka Wars	This is what happens when you apply tandem control to a real-time military strategy game.
	Combat	In several of the plane game modes, players control multiple planes which move in tandem.
	Galaga	If one of your fighter ships are captured, and you destroy the command ship that took it, you will control two fighters in tandem.
	Home Run	Some of the game modes have multiple players moving in tandem as the fielding team.
	Video Olympics	Many different game modes feature tandem controls.
	Volleyball!	The player moves all six members of their team in tandem.
	Wrath of the Black Manta	The ninjitsu art of the shadow creates a second character that moves in tandem.