Nice! So many fond memories of pinched fingers, screwdrivers slipping, wrenches flying off...
The smell of all those metal parts, coveted pulleys and gears and the 'clear' plastic sheets that would eventually crack and tear... and the holes lining up, almost, but close enough to jam a longer bolt into and pry them into a better fit.
Meccano cranes, bulldozers, cars and towers, forklifts and tanks, planes and just when we thought it couldn't get any better, our neighbour gave us a steam engine his boys had outgrown!