Thanks for playing! :D
I see what you mean, thanks for mentioning it. It's because itch thinks when you press esc you want to exit the game. But it's also the options menu. I could probably prevent this next time by doing what you said. For now if you press esc again (that opens the options menu) and then click continue the mouse does get locked in the screen again.
In godot it is Input.set_mouse_mode(Input.MOUSE_MODE_CAPTURED). I do use this when the game gets loaded for the first time and when you click on continue in the options menu. But should also use this when you click the game screen again. Good to know for next time! Thank you!