Thank you very much. I actually thought about changing colors over time or over spawned elements. i had one version where those energy-echos slowly turned orange. but that wasn't the solution as it made everything more confusing. maybe some more distinct random colors would have helped.
The wheels (as well as all the other inputs) are completely physics-based so yes, gravity pulls slightly on them. the have a definable resistance. the was a small problem with higher distance where the wheels started jumping around, so i went with the lower resistance.