I've been writing an archetype-based ecs (entity-component-system) library for picotron and i put it up on github!

https://github.com/snowkittykira/picobloc

It keeps component values in picotron userdata so that for simple cases like velocity / acceleration, you can use userdata operations to make it very fast! As a result it is probably slightly harder to use than the other ecs libraries available for picotron right now (which use tables to represent entities), but should allow some pretty good optimizations.

you can see the example from the readme running here:

https://www.lexaloffle.com/bbs/?tid=141824

and my plink cart also uses it, though it doesn't really need the optimization:

https://www.lexaloffle.com/bbs/?tid=141789