Legos !
Those were so fun, although I'm not sure I've had any in my hands since I was a child. I don't remember there being such complicated builds, more of a large pack of Legos, small suggestions and our imagination to make things up. One of my nephews was a Lego whiz though when he was very small. He has 6 unruly kids of his own now. I am wondering if he still has his Legos of old or if his minions have scattered them to the ends of the farm. LOL.... I may be inclined to ask one day.
I'm sure you are having great fun !