To build an IR receiver that triggers a relay for a light in a game, consider using pre-built IR receiver modules and their corresponding transmitters, which are widely available online. These modules can simplify the process for those with limited electronics knowledge. The design requires the IR receiver to detect signals from an IR gun, activating a relay to turn on the light until it is manually reset. Additional resources and images can be found through a simple Google search for "IR receiver module." This approach provides a practical solution for integrating IR technology into your game design.