Hey! Thanks for wanting to check out the game. We don't fully understand why, but hardware acceleration causes that extreme lag. There is a Windows download that has no issues in the downloads as an alternative.
Until we solve this issue you can also toggle Hardware Acceleration on Firefox by going Settings -> General -> Performance and unticking the two boxes there. Then re-enable it when you're done.
I couldn't recreate the chrome bug so hopefully that is also caused by this issue
Just pushed an update hopefully the web version is working properly now.