Or does c# reflection work differently from java?
Looks great by the way.
If you want to support complete reflection across the board it greatly swells compile size, but I have made it so you can be selective about what supports reflection, in order to avoid code bloat.
How much do the threads actually work yet? How slow are they?
Real threading would have to use ES6 yield/generators to translate an entire thread into a spawn loop so that async/await blocks can be emulated.