To me, it would have felt more natural to control the aiming Angry-Birds style, where you pull back to aim, rather than put your cursor where you want the magnet to go.
Also, there was at least one level where the magnet spawns behind where your player starts. Just a little thing, but it was annoying every time I restarted, I'd have to go backwards a bit just to grab the magnet.
Overall, I think you're off to a good start! Definitely love the visuals! The gates were especially fun to play around with!