Algodoo

Your "Clear Tracers" button does not work. Use the following or fix it some other way.

in console:
scene.my.pens := []

in tracer onSpawn:
scene.my.pens = scene.my.pens ++ [entityID]

in button onClick:
ra := [];
n := string.length(scene.my.pens);
scene.my.xFor(0, n-1, (i)=>{
thispen := scene.entitybyID(scene.my.pens(i));
newpen := Scene.cloneEntityTo(thispen, thispen.pos);
scene.removeEntity(thispen);
ra = ra ++ [newpen.entityID];
});
scene.my.pens = ra;

Save and then open the scene for the changes to take effect.