Yes, but when you write in a high-level language like javascript without taking advantage of all of the high-level features like webgl (which are provided by th

Yes, but when you write in a high-level language like javascript without taking advantage of all of the high-level features like webgl (which are provided by the implementation and assumed to be fast), performance suffers. In this case, Notch is writing code that doesn't necessitate the overhead of using JS. It could easily be rewritten as C and probably run faster that way. Not that it isn't interesting, of course.