Oh, so you want particles?
You need only two objects for that too (Sprite, Particle)
Sprite - Platform is moving >>>
- Particle | set position to (Sprite.X, Sprite.Y)
- Particle | set rate to 35
- Particle | set angle to Sprite.Platform.MovingAngle + 180 degrees
Else >>>
- Particle | set rate to 0
When is moving, the particle is set to the Sprite position, and the rate is set to normal. Also, the angle is set to the opposite of the Sprite moving angle.
When isn't moving, the particle rate is set to zero, and it doesn't appear.
LINK: https://www.dropbox.com/s/ajc71c4lg8ec9ze/help.capx?dl=0