public static Pose TurnLeft(Pose startPose, Gear gear, float turnAngle, float unit)
        {
            if (gear == Gear.Backward)
            {
                turnAngle = -turnAngle;
            }

            float phi    = turnAngle / 2;
            float sinPhi = (float)Math.Sin(phi);
            float L      = 2 * sinPhi * unit;
            float x      = L * (float)Math.Cos(phi);
            float y      = L * sinPhi;

            Vector2 pos = new Vector2(x, y);

            pos = Vector2.Transform(pos, Matrix.CreateRotationZ(startPose.Orientation));

            if (Debug != null)
            {
                float rotatedTheta = startPose.Orientation + (float)Math.PI / 2;
                float xCenter      = startPose.X + unit * (float)Math.Cos(rotatedTheta);
                float yCenter      = startPose.Y + unit * (float)Math.Sin(rotatedTheta);
                Debug.DrawArc(new Vector2(xCenter, yCenter), unit, startPose.Orientation - (float)Math.PI / 2, startPose.Orientation + turnAngle - (float)Math.PI / 2, gear == Gear.Forward ? forwardColor : backwardColor);
            }

            return(new Pose(pos + startPose.Position, startPose.Orientation + turnAngle));
        }