@danijoo: Unity's "Java Script" is not actually Java Script, it's their own implementation that has significant syntax differences (classes, type declarations, etc.), so I would be surprised if Kotlin JS would work out-of-box. Also, Unity's Java Script is compiled to Mono, so there's no code delivery benefits from using it vs C#. There's some third party libraries for binding actual JavaScript VMs (spikermonkey), but it looks like there's much less activity in that area compared to Lua Unity bindings, where there's several competing libraries/approaches