Dealt with it, it was an issue with old g*dot version refusing to regrab focus onto game iframe.
Now you can grab focus with mouse and it will once again accept keyboard inputs.
Viewing post in To Slay the Dragon [combat demo] jam comments
Great! Got it working. The first time through, I broke the combat system by flailing and pressing too many buttons at the first set of attacks. I tried to reproduce it but I wasn't able to. I tried again and got the hang of the battle system. I feel like there's a lot of depth there that could be explored in a proper tutorial. Loving the aesthetic and audio so far, keep it up!