I have received my first MEL Kids set about hydraulics and it’s amazing! The quality of the materials is good and the step-by-step instructions are easy to follow. A comic story leads you through serious concepts like pressure and molecules; while I couldn't quite appreciate it myself, I think it kept my niece engaged.
Eventually, we've built a hydraulics lift with just syringes and tubes, and I think she's quite ready to lift the house with it. The tubes come off occasionally, but an improvised water gun battle can be fun too.
P.S.: I've taken a photo of the kit's contents before we've assembled it; sorry for the mess on the floor. A good 80% of it has been covered with toys ever since COVID.
P.P.S.: it has some wooden pieces, and if you're into the smell of fresh-cut wood, you're gonna love this one!