I think the lightning / thunder timing mechanic is honestly pretty creative - that's a great way to incorporate the theme. I also like the MS Paint style graphics at the intro to the game lol. Biggest issue was definitely the lag - it could be that I have a slower computer, but the game was extremely laggy for me, so any way to optimize it would be nice. Also, I think have the UI be more custom built, rather than the standard assets (like give them a unique look with some images, making it look less just like plain text on the screen and the default Godot sliders) would go a long way to adding identity to the game. Overall, though, nice work - keep it up!