Thank you! I can't take any credit for the performance though since I just used an existing engine (https://love2d.org/), which has an Emscripten based web exporter readily available (https://github.com/Davidobot/love.js). The actual game part is written in Fennel (https://fennel-lang.org/), which is then compiled to Lua and executed by LÖVE.
This was my first time using LÖVE but I can definitely recommend it for making 2D games, easy to learn and allows for very fast prototyping!