Thank you I'm glad you liked it!
And yeah I need to do more testing to find a good balance for all the player stats, as well as making sure the upgrade/downgrade system doesn't break anything else haha, and yes I wanted to add a sprite "blink" when you get hit or hit an enemy to address that issue but sadly couldn't finish it in time, for the bug where pressing space doesn't start the game I don't know what causes it, I think it has something to do with Unity interacting with the website, it happened to me too and I couldn't find a fix for it.
again thanks for playing and I'm glad you enjoyed it!