A biofeedback game is one in which the player is connected to the computer through some device reading the pulse, breathing rate or other sign of life of the player, which device is then used to influence the game, turning the player into a joystick, as it were. The input can serve any use the programmer wants, ie. to make the on-screen character run faster, sweat more; to cause a storm in the game, hyperventilate, etc. The possibilities are mind-boggling, yet the number of games is few, for a number of reasons: first, the apparatus needed to measure the player's signals will be complicated, clunky and more costly than the game itself. Second, other than "teach yourself how to relax" games, what other games need this kind of hard to measure and, often, frustratingly hard to produce signal, that could be so cheaply and easily replaced with mouseclicks? Thirdly, if a game really did ask the player to hyperventilate, someone could get hurt; a full-blown hyperventilation attack, though not fatal, feels like a near-death experience.
So, the genre is pretty much restricted to "teach yourself how to relax"
games. Although "biofeedback" is not properly a genre; the game itself could be
arcade, adventure, RPG, visual novel, even simulation, depending on how the body
signals are used. In practice, though, "adventure" is the most compatible genre,
and the puzzles will mostly be "how do I get my heartbeat rate down/up".