I, Cyborg is a shooter set in a partial 3-D environment viewed in a behind the player perspective. Somewhat presented in the same manner as the unreleased Dark Tower, the player moves a big cyborg throughout several levels, seeking revenge after being wrongfully imprisoned and either avoiding or destroying everything in its way.
As the player moves throughout an Area, at various times a trap will be triggered, releasing an enemy (or a set of them) from the top or side areas of the screen, which will then attack the cyborg. Enemies either come out in a set number, while others will keep on reappearing indefinitely until the player moves forward a certain amount until the trap deactivates itself. Enemies can also shoot or ram into the cyborg, causing damage, which is denoted by a number on the cyborg's back. The cyborg starts each area or phase with 10 health units, which a collision with an enemy or its weapon will drop the cyborg's health down by one, except for an encounter with Decapitators, which will instantly end the game upon contact. Meanwhile the cyborg can counterattack with an acid mist weapon that can be aimed in three directions.
Each Area (except for the final one) is comprised of four Phases, plus an end of Area boss, which the player is granted a special weapon that can only be used against that boss in particular (the player's regular weapon's firing range will not reach any of the bosses). Keycodes are awarded to the player after defeating each Area so they can just skip to that level, rather than starting each game over from the beginning. The codes are unique to each game and were released by creator FURY once all copies of I, Cyborg sold out (during its initial run; see Trivia).