GUI or not GUI?

I’m currently making a game called “TIRED” where the main mechanic is energy. So, before staring making the levels I came up with a big question: GUI or not GUI, that is the question

The point is this: I wanted to make this role playing game as immersive as possible, where you feel to be the character, not to play as him, something like undertale. And so, I thought that a graphic user interface isn’t the best for making you feel to be Hlu, but I have to show in some way the nergy that is left to you, for making you understand whenever do something and whenever stay still for recharge your energy. So, first I tried, because you can’t say that you dislike something if you didn’t try it out, but the result were really bad, as I expected,, so after thinking I came up with this idea: the screen will get darker when you lose energy, so the player will know that he is running out of energies when the screen gets darker, it also fits perfectly the story of the game that I can’t tell you.