Hammer's Input/Output system is an incredibly versatile tool that is very simple to use and understand. Each entity class has a multitude of different inputs and outputs that can be activated with simple trigger entities. Trigger_once entities fire outputs once while trigger_multiple entities trigger some things as many times as you want. Filters are powerful tools that let you control exactly which events are triggered by which entities. Now that you know how to harness the power of the input/output system, let's have some fun with cameras and track trains!