Apparently according to the comments you are supposed to throw the magnet at a pipe and the pipe is supposed to suck it up. But I was not able to get the pipe to do that for some reason. I did try to throw the magnet in to the pipe a few times and then I got frustrated and gave up. This was on the very first level. Apparently you can click on a button that says "Back to Hub" when you pause the game before you even have seen the hub for the first time. So when I gave up on unlocking the door on the tutorial level, I clicked on the button named Back to Hub (which took me to the hub level) to see if I could enter any levels and I couldn't throw the magnet to enter any other level. How do you aim a magnet so that it sucked up by a pipe? do you need to increase particle field sucking up effect?
Edit: after a few trys and reading a few comments, I realized I needed to change the polarity of the magnet but throwing a magnet into a pipe still feels a bit clunky. And if you manage to throw the magnet into a pipe you didn't intend to throw it into in the hub world there doesn't seem to be any way to get it back.
Also, what does the reset button actually reset programmatically? because I got stuck on this level
and when I pressed the reset button the reset button pressing animation played but the scene wasn't reloaded for some reason and if I wanted to re-attempt the level it seems that I would have to exit to the hub and deal with the clunky hub world design and then go back it the level to try again. (At least I thought that was what I had to do but after opening and closing the game a few times I managed to see the reset level function actually work)
Also, after opening and closing the game a few times I realized that your game starts from level zero each time. Maybe you could implement a function to save the game progress when you quit or something similar.