As far as the Lego adder, it introduces a very tricky question, of what constitutes an implementation or instantiation of an abstract machine or algorithm. This is an issue which has been of some dispute among philosophers. One approach is to see if you can create a map between the physical system and the abstract system, where the algorithmic complexity of the map is small compared to the complexity of the system. Unfortunately this does not give an absolute answer, because of ambiguity in numerical measures of algorithmic complexity.