Hot Wheels went next level when Sizzlers came out in the 70s and were even cooler they made the Fat Track.
My brother and I got 2 Fat Track sets one Xmas, so we combined em for a giant ass layout with several cars racing at once...shit was like Daytona.
The biggest drawback to Sizzlers, tho, was you had to charge em up for a few minutes with the Juice Machine and they only ran for a few minutes.
The evil genius I was, I plugged my car up to a Juice Machine and strapped a D battery to it and had that bitch overcharge for several hours...shit worked like a charm.
I think we modified every toy we had...which is why most of our shit was destroyed pretty quick.