El Poder Oscuro is an action adventure game heavily influenced by Mazinger Z. The game sees a player piloting a large mech called X-R-2 trying to escape the titular "dark power", a black wave that creeps into each screen over time from left to right. As the game progresses, the player will have to find ways to open paths for the X-R-2 mech by deploying a detachable ship that has the ability to fly or to jump out of the ship itself to access narrow pathways on foot. The game is over when the human character is killed or the "dark power" catches up with him.
The game is structured like a navigation puzzle, where the different abilities of the three characters are used to unlock paths for each other, but there is a run-based component to it as well, with the game often presenting inescapable pitfalls that will get a character stuck without exit until it is consumed by the dark power. Eventually, the goal of the game is to figure out the sequence of actions to take (and avoid) in order to bring the X-R-2 mech to the rightmost end of the map, where it will acquire a beam weapon to destroy the dark power and complete the game.