great game with interesting mechanics, really liked how the first few levels of the hub were sorta like a silent tutorial.
the last puzzle was a massive spike in difficulty though
two nitpicks: the level ending on picking up a key felt a bit strange -- in most other games they are used to unlock something in the current level so maybe the item that ends each room could be changed, or you need to the walk the key back to an exit door?
having to pick up the magnet at the start of each room is a little annoying, maybe spawn in holding a magnet if its a room where you want to give the player the magnet immediately?