Hello, I was wondering why I always get an error message when using the script for MsPhysics. Here's the script

Triggered when simulation starts

onStart {

Have the desired velocity as 5 m/s

@des_vel = 5
}

Triggered every time the world updates

onUpdate {

Compute the force to apply

timestep = simulation.update_timestep # (in seconds)
force = this.mass / timestep # (in Newtons)

Get current velocity

cur_vel = this.get_velocity

leftx() returns a value ranging from -1.0 to 1.0, depending on the state

of A and D keys or the horizontal position of the left joystick.

fx = (leftx() * @des_vel - cur_vel.x) * force

lefty() returns a value ranging from -1.0 to 1.0, depending on the state

of W and S keys or the vertical position of the left joystick.

fy = (lefty() * @des_vel - cur_vel.y) * force

Apply force on this body.

this.add_force(fx, fy, 0)
}

Not sure what I'm doing wrong.

Thanks