Hey! Thanks so much for playing! It appears that a bug is present where the attack indicator is not always triggered, and since I was in a rush to finish the game art, I completely forgot to draw some kind of indicator on the sprite itself :(
Regarding the restart, pressing the "R" key should work. I checked with a friend and from what I saw, it can happen that the focus on the game window is lost and so the action doesn't trigger.
Thanks again for playing, really appreciate it :)