It is a solid idea for a puzzle game.
I really like how you interpreted the idea of "loop" for this game.
I do think however, that getting the ball back to the start should be something explained in the game itself, and not just the Itch.io page
I'm unsure if there are only 2 levels or if there is some kind of bug. But I was only able to play the first 2 levels, the other 4 seemed to be locked with no explanation.
I do like that there is a star in level 2. Because otherwise, you can sort of just do the same thing to do the loop in each level. I think that some levels should be unlocked once you have a specific amount of stars so that you have to actually play the level.
I do think that while the building mechanics are impressive, there are some issues with them.
1. Sometimes the simulation can be different for no reason. Sometimes when I hit the simulation button, the balls go one way, and when I hit it again, without making any changes, they go somewhere else, which can make it hard to create a path for them.
2. You have a limit on the objects you can use, which is great. However, picking up an object that has already been placed and then putting it back down, uses one of your object uses for that object, which seems rather unfair and seems also like a bug.
3. Clicking reset does not reset the amount of objects you have for the level, so the only real way to reset is to go back to the main menu and then go back to the level.
All three of these bugs together make the game a little bit annoying as the balls can act differently each time, and you only have one shot to test your idea, because trying to fit it will cause the game to bug out and give you less items.
I suppose you could place every object first and then be able to move them around, because the game doesn't stop you from doing anything once you reach 0 or the negatives, just that it won't let you place more new objects. But this seems unnecessary and unintentional.
Also, there being 3 levels on the main menu, but 6 levels when you beat a level is confusing and it should have the same number of levels in both menus to make it more understandable.
The music is very relaxing and nice and fits the atmosphere of the game well, however, it does not appear that it loops, or at least loops correctly, which is sad.
I also enjoy the models for the game. Sure, they are pretty simple, but they give a nice look to the game that I very much enjoy.
Overall, it is a solid base for a game, however, doesn't have enough levels to really establish itself and some pretty big bugs which hurt its enjoyability.