According to Energyblast, "Built with the WebAssembly/GO language and JavaScript https://energyjp.itch.io/energy-webmugen This is not a download, rather me wanting to show off what I did. A fully playable Mugen inside your browser. I would like your thoughts and bug reports in the appropriate itch.io thread. The goal was to provide an easy to mod UI for people to host their mugen builds on a website."