Algodoo

{cos(cos(sim.time * 2) * 1.2500000) * 4}

Put this into the "size" part in the tracers script menu

The "sim.time * 2" is the speed, to quicken the scaling make this higher, to slow it, make it smaller.

The "*1.2500000" is for the smallest/largest the tracer will scale to. This value works best when slightly above 1, but will still work for any other values

The "*4" is the maximum size the tracer will go to.

Any questions just post a comment!