Nope, no errors.
However, I've narrowed the issue down to the CRT shader. Disabling that makes the game work. It' odd, though, I've never had problems with shaders before (in Godot or anywhere else), and it displays fine in the editor. Anyway, I was able to play the game now... You should probably have dropped that countdown, it just adds to the frustration of a game over having to wait so long before you can try again, with such a difficult game. I'd probably had the patience to try a little harder if it wasn't for that :P