In general, **controllers** are devices, components, or software modules that manage, direct, or regulate the operation of another system or process. They take input (often from sensors or user commands), compare it to a desired setpoint or expected behavior, and then send output signals to make adjustments that achieve or maintain the target conditions. Controllers are commonly found in engineering (e.g., in control systems), computing (e.g., in software architecture like model‑view‑controller), and hardware devices (e.g., game controllers).