I'm no good when it comes to constructive criticism, especially when it comes to video games, but I'll give it a shot anyways;
First off, massive step up from the MVP. Our robot hero has a much better visual appeal, and the magnet has a lot more character attached to it. Each level presents a new challenge for the player, where they make use of their environment in different ways every time.
Every time I completed a level, I always got frustrated at myself for not realizing that I should have won the level in that particular method. I am no game design expert, but I think that putting the player in a spot where they have no-one to blame but themselves is really effective in terms of engagement and motivation.
One point I could make is that sometimes, the player has solved the puzzle, but has to apply their platforming skills to win the level. This merge of genres may hinder motivation of some players.
Another thing is that a lot of the times, I found myself restarting levels a lot for say, falling in pits too deep to get out. Unless this is intended, this could be changed in some way to remove the fatality of small mistakes. Whenever it is intended, add spikes so the process is quicker.
I also suggest some minor UI improvements, like for the metal bars that aren't attracted by the magnet, but are attracted by magnetic bars of opposite polarity. I see that you have indicated this by showing a metal outline surrounding the polarity mark, but maybe an arrow showing which way it will attract or different colours may help.
As a few others have pointed out, the beam that destroys magnets definitely needs a visual change. The smiley face will almost certainly confuse players for the first time, especially the colour, which they may mistake for polarity. Another symbol, like an X would do I suppose. However, it is a clever mechanic and something you must include in future levels.
My final point is that on the final level, where the solution is to get the metal box stuck between the levers, I think that it should be made a bit more clear that this is the way to do it. Maybe a player might notice this, but I definitely did not see this as a possibility when I first tried the level. But using mechanics as physically manipulatable objects in levels is quite clever and encourages the player to treat the levels and their objects in another manner.
I'm intrigued to see where you take the game next. I'd love to see you scatter gameplay ideas experimented here in the full release. I also want to know what parts of the game you want to tackle next; when you get to that point, how will you incorporate a story based around your game. How can the music influence the gameplay?
Although this wasn't very comprehensive or informative, I hope it helps in some way in terms of player feedback, and that you see where I'm making my judgement abouts.