I can't believe this is the first game you have ever made from scratch. It motivates me to learn more myself. Amazing job!
One thing I've noticed is the aiming system. The movement is controlled by the arrow keys but the aiming is by the mouse. Each time I wanted to aim at something was a mini "forced-back-to-the-reality" moment since I have to remember to let go of my arrow keys to reach the mouse, then come back to the arrow keys once again after throwing the magnet.
I thought that it'd be better if the movement is also controlled by the mouse since you are disabling the movement while aiming. Click and move toward style.
Overall, the puzzles were pretty satisfying to solve and I really liked the main character's movement. Basic controls like move and jump were pretty smooth as well (I remember you mentioned overhauling the player control system in one of the videos). I played with the Mac version but I didn't notice any bugs.
I always enjoy your video series and learn a lot from them. Keep up the great work you are doing! :D