Thanks for playing and leaving feedback! :D
There is an audio options menu if you press Escape whilst the game is active (no other menu open) but on Itch.io that never works so nicely because it takes you out of full-screen as well. I agree though that I should add one to the main menu next time!
I reaaaaally really recommend Godot, especially for 2D games. It's quite easy to pick up, once you understand the node system it's really easy to experiment with it, and there are more and more tutorials for it all the time. I find it makes 2D games much easier than Unity and it has way better UI options than gamemaker, and it comes with a lot of features that I find really helpful. And being open-source is a great plus.