Now I was able to test it, it was just a matter of pressing enter as you said, I played the webgl version.
Your game is really good, seriously, it's great. It's awesome that is your first finished game.
The gameplay it's pretty simple, but that's expected for the scope of a game jam. What I really liked was the effort put on the details. Good SFX, nice animations, enemy life meter for feedback, camera shake for added game feel. Everything combined make it look really polished, even being so simple at the end.
You said in comment before that you not an artist. However, the animations, specially the player attacking (with anticipation, nice) were very good.
The only thing I wish was different is that I would like to be able to walk while attacking, but I can see an argument for the other way, is just my preference to feel that I have more control over the character.