Unity Input System (new)

Read input through Unity's Input System package (com.unity.inputsystem, 1.x) —
action-based, device-agnostic, rebindable. Targets Unity 6.3 LTS. This is the modern
replacement for the legacy Input.GetAxis/Input.GetKey Input Manager.

When to use

• Use when setting up movement/jump/fire input, defining an .inputactions asset with
  action maps and control schemes, wiring a PlayerInput component, reading a Vector2
  stick/WASD value, or handling gamepad + keyboard + touch from one set of actions.
• Use when Packages/manifest.json contains com.unity.inputsystem or the project has an
  *.inputactions asset.

When not to use: rebindable-control architecture across engines → input-systems
(this skill is the Unity-specific API). Moving the character once you have the input vector
→ unity-physics / unity-csharp-scripting.

Core workflow

1. Check Active Input Handling (Project Settings → Player). The package only receives
   input when this is Input System Package (New) or Both. Both is required if any old
   Input.GetAxis code remains.
2. Create an .inputactions asset. Add an action map (e.g. Gameplay), add actions
   (Move = Value/Vector2, Jump = Button, Fire = Button), and bind them to controls and
   composite bindings (WASD = 2D Vector composite).
3. Choose how to read it:
   • PlayerInput component (designer-friendly) — drop it on the player, point it at the
     asset, pick a Behavior (Send Messages / Broadcast / Invoke Unity Events / Invoke C#
     Events). Best for single/local-coop players.
   • Direct in code (InputActionReference / InputActionAsset) — most control; you
     Enable() actions and read them. Best for systems and tools.
4. Enable the actions/maps you read. PlayerInput enables its default map automatically;
   actions you reference yourself must be .Enable()d (and disabled on teardown).
5. Switch action maps for context (gameplay ↔ UI/menu) instead of guarding every handler.
6. Verify with the Input Debugger (Window → Analysis → Input Debugger) to confirm devices
   and that actions fire.

Patterns

1. PlayerInput with "Send Messages" (handlers on the same GameObject)

using UnityEngine;
using UnityEngine.InputSystem;

// PlayerInput (Behavior = Send Messages) calls On<ActionName>(InputValue) by name.
public class PlayerInputReceiver : MonoBehaviour
{
    private Vector2 _move;

    private void OnMove(InputValue value) => _move = value.Get<Vector2>();   // Move action
    private void OnJump(InputValue value) { if (value.isPressed) Jump(); }   // Button action

    private void Update() { /* drive movement from _move */ }
    private void Jump() { }
}

2. Reading an action directly in code (polling a value)

using UnityEngine;
using UnityEngine.InputSystem;

public class DirectMover : MonoBehaviour
{
    [SerializeField] private InputActionReference moveAction;  // assign the Move action

    private void OnEnable()  => moveAction.action.Enable();    // REQUIRED or it reads zero
    private void OnDisable() => moveAction.action.Disable();

    private void Update()
    {
        Vector2 move = moveAction.action.ReadValue<Vector2>(); // continuous value
        transform.Translate(new Vector3(move.x, 0, move.y) * (5f * Time.deltaTime));
    }
}

3. Event callbacks + switching action maps (gameplay ↔ UI)

[SerializeField] private InputActionAsset actions;

private void OnEnable()
{
    actions.FindAction("Gameplay/Fire").performed += OnFire;  // edge event: fires once
    actions.FindActionMap("Gameplay").Enable();
}
private void OnDisable() => actions.FindAction("Gameplay/Fire").performed -= OnFire;

private void OnFire(InputAction.CallbackContext ctx) => Shoot();  // ctx.ReadValue<T>() if needed

private void OpenPauseMenu()                       // change context, don't sprinkle if-checks
{
    actions.FindActionMap("Gameplay").Disable();
    actions.FindActionMap("UI").Enable();
}
private void Shoot() { }

Pitfalls

• No input at all → either Active Input Handling is still Input Manager (Old), or you
  forgot to Enable() the action/map. PlayerInput auto-enables; raw InputActions do not.
• InvalidOperationException about the old input backend → some script still calls
  Input.GetAxis/Input.GetKey while Active Input Handling is New. Port it or set Both.
• Buttons read as 0 with ReadValue → button presses are edge events; use the
  performed callback (or WasPressedThisFrame()), not per-frame ReadValue for triggers.
• Send Messages handlers never fire → the receiving script must be on the same
  GameObject as the PlayerInput; Broadcast Messages reaches children too.
• Leaking subscriptions → unsubscribe (-=) in OnDisable; re-subscribing in OnEnable
  without unsubscribing doubles up handlers.
• Touch/gamepad not detected → enable the matching control scheme and confirm the device
  in the Input Debugger; the Vector2 composite needs all four bindings set.

References

• For interactive control rebinding (PerformInteractiveRebinding), saving/loading
  bindings as JSON, and local multiplayer with PlayerInputManager, read
  references/rebinding.md.
• Primary docs: Unity Manual "Input System"
  (https://docs.unity3d.com/Manual/com.unity.inputsystem.html).

Related skills

• input-systems — engine-agnostic input architecture (rebinding, buffering, multi-device).
• unity-csharp-scripting — the MonoBehaviour these handlers live in.
• unity-physics — applying the input vector to a Rigidbody.