I'll be honest, like most of you, I'm getting fed up with open world games. I've reached the point of vomiting, especially seeing open world games filled to the brim with the same stuff. And that's why I can safely say to you that Tunic is not one of them. So yes, it's partially open world, but just like a classic Zelda game world. Let me explain…
You are a fox and you slay your enemies with a sword.
Tunic's world seems like an open world at first. A beached fox gets up, writes something in languages you don't understand, and you try to find your way by trial and error. The things I have explained so far may sound like any open world game, but with the lack of equipment and the overpowering enemies, you say "Yes, this is not the place" and move towards the path that it forcibly directs you. (Link's Awakening?)
Along with these, you start to see how the game is inspired by Zelda as a design. For example, when I first started the game, there were places that I could not understand how to go. When I cleared a dungeon and at the end of the zone, the game took me out in a place like behind a wall in the Overworld, I realized that there are also secret passages where the camera angle of the game does not show. After learning this, I started pushing our poor fox to every coastal corner place I saw.
As you can see, the game encourages you to explore its map abundantly, and you get it in return by strengthening your fox or finding hidden paths. With some special materials you will find around (I won't tell you what they are, discover it), you can increase your fox's health, durability, the amount of health that potions can complete, or you can also come up with disposable useful things such as gold and bombs. The secret paths you find can lead to a place you have never been to before or turn into a shortcut. These come in handy too, because in addition to being Zelda-inspired, the Tunic also has a lot of Metroidvania elements. The regions you visit offer things that you will want to return to again and again. But as you explore the little game, you realize that Tunic's colorful, low-polygon art design is purely to trap the player, just like a sneaky fox...
As I said, Tunic starts out as one of the cutest games in the world, let me draw a little picture for you. Now imagine, as a fluffy fox you land on a colorful island and the first weapon you get in the game is a straight stick. You see a couple of slime-like creatures around, they die in two or three hits with your stick. Then you enter a dungeon, you see the huge creature with a sword in its hand. After you barely pass with your stick, a boss appears in front of you. Because Tunic doesn't have any difficulty settings, just like a Souls game, it just says "Go ahead". Although the boss fights of the game are not as much as From Software productions, they are definitely compelling and memorable.
But if at the end of the day what you're looking for is an "unprecedented game", unfortunately, Tunic is not that game. It doesn't do anything the gameplay-inspired Zeldas or Souls don't. I can't say that it offers such a wonderful thing as a story either. But as someone who likes the "journey" feeling of Zelda games in particular, Tunic satisfies this feeling very well. Especially their music and world seem to accompany me for a while. I still have a hard time believing that this game was made by a single person.