R0J0hound - thank you. I will give this a try, although I am not sure if it's what I think I need... Would it work in the case of a plugin like scirra's Physics - ie, is behinstProto.tick called before the rest of the plugin script models the world and, if so, how do I measure the end of the world's calculations? I guess I am struggling to visualise the relationship between the plugin script, the tick function and the c2.runtime (and, as I type, perhaps I need to dissect how that plugin's use of processing time is measured for the debugger). Cheers.