Inventory2/player/CameraController.cs

public partial class CameraController : Node
{
	[Export] public Camera3D Camera { get; set; } // Will be `null` for remote players.
	[Export] public Vector2 MouseSensitivity { get; set; } = new(0.2f, 0.2f); // Degrees per pixel.
	[Export] public float PitchMinimum { get; set; } = -85;
	[Export] public float PitchMaximum { get; set; } =  85;

	public Transform3D DefaultTransform { get; private set; }

	public float CurrentPitch { get; set; }
	public float CurrentYaw { get; set; }

	public static bool IsMouseCaptured
		=> Input.MouseMode == Input.MouseModeEnum.Captured;

	Player _player;
	public override void _Ready()
	{
		_player = GetParent<Player>();

		if (_player.IsLocal) {
			DefaultTransform = Camera.Transform;
		} else {
			Camera.QueueFree();
			Camera = null;
		}
	}

	public override void _Input(InputEvent @event)
	{
		if (!_player.IsLocal) return;
		if (IsMouseCaptured && @event.IsActionPressed("ui_cancel")) {
			// When escape is pressed, release the mouse.
			Input.MouseMode = Input.MouseModeEnum.Visible;
			GetViewport().SetInputAsHandled();
		}
	}

	public override void _UnhandledInput(InputEvent @event)
	{
		if (!_player.IsLocal) return;
		switch (@event) {
			case InputEventMouseButton { ButtonIndex: MouseButton.Left, Pressed: true } when !IsMouseCaptured:
				// When left mouse button is pressed, capture the mouse.
				Input.MouseMode = Input.MouseModeEnum.Captured;
				GetViewport().SetInputAsHandled();
				break;
			case InputEventMouseMotion motion when IsMouseCaptured:
				ApplyRotation(-motion.Relative * MouseSensitivity);
				break;
		}
	}

	void ApplyRotation(Vector2 delta)
	{
		delta *= Tau / 360; // degrees to radians
		CurrentYaw   += delta.X;
		CurrentPitch += delta.Y;
		CurrentPitch = Clamp(CurrentPitch, DegToRad(PitchMinimum), DegToRad(PitchMaximum));
	}
}