Light bulbs are a recurring item within the series, appearing in Submachines 2, 5 and 7. Although variants appear in most of the games, only a few can be picked up and used.
Submachine 2: The Lighthouse[]
The player finds the light bulb in a strange box on the second floor. After inputting the code and pressing the button, the light bulb can be collected. The light bulb is a projector bulb used in the basement.
Submachine 5: The Root[]
The light bulb is found in the metal box room (cipher plate: 1,2) and is used to light an area within the ancient room (cipher plate: 2,1).
Submachine 7: The Core[]
In Submachine 7: The Core, the light bulb is found in one of the force field projectors in the sanctuary. It can only be picked up once the projector is switched off using the key-card.
It is used in the basement of Liz's ship where the bulb is missing.
Although not an item the player picks up, a similar bulb is broken by the player to remove the second force field in the sanctuary.