My main issue is the cross-prototype calls in the power creep like this:
PowerCreep.prototype.moveTo = register.wrapFn(function(firstArg, secondArg, opts) {
if(!this.room) {
return C.ERR_BUSY;
}
return globals.Creep.prototype.moveTo.call(this, firstArg, secondArg, opts);
});
It looks innocuous but there's a problem here; It goes against expectations (and general OOP). Creep.prototype.moveTo is expected to only be called on creeps. Therefore any overrides, any internal behavior of moveTo, expects this to be an instance of a Creep, or a class derived from one. A PowerCreep is neither, it's an entirely separate class abusing the scope of a Creep method. There are several methods and properties like this, that could be written once and reused, but the only common base is RoomObject which for obvious reasons is too abstract for this.
I understand why a PowerCreep can't simply be a child class of Creep, too many differences. But If you find yourself writing calls like this it's time to consider writing a shared based class.
This would allow for things like hits, carry, moveTo, my, owner, etc and any other methods or properties identical between the two to be written once and reused across as many types of actors as you want.
I'm a strong proponent for having a shared base class. Due to the way prototype inheritance works, adding such a prototype to the engine would not cause any breaking changes to existing player code.