System Mania is a management game where the player must flip switches, turn cranks and press buttons to fix machines. Each one of the 90 levels is a different machine, with an array of controls scattered around the screen. Using the mouse cursor, the player must interact with the ones that have a red warning light on. When fixed, the controls often throw bonus medals that must be quickly collected, before falling to the bottom of the screen.
Switches and buttons only require one mouse click to be fixed. Wheels and cranks need to be turned around a couple of times to turn off the light. Cords have to be pulled by their handle. Sliders need to be dragged to a red indicator. Strings have to be plucked. Hourglasses need to be turned upside-down to move the sand to the other compartment. Some buttons have doors that open and close over them all the time, requiring precise timing to be pressed. Dials have to be turn to the number indicated in the red light. Gear sticks need to be placed on the correct position, also indicated by a number in the red light. The keypads have a numerical sequence displayed besides the red lights that must be typed in. The piano has a number assigned for each key, and the display shows the numbers of a tune that must be played. The TV has a joystick and a button, and the objective is to move a targeting cross over a square to destroy it.
Each interaction gives a small amount of money that can be spent on power-ups, in a shop between levels. They appear as three yellow buttons on the screen, that help by slowing the game speed and changing other gameplay parameters. Random events occur to provide additional challenges, where the lights turn off, darkening the screen with the exception of a halo around the cursor, and steam clouds cover the screen making everything more difficult to read.