Lean a cookie sheet or large hardcover book against a couch cushion to make a ramp. Place 2โ4 toy cars at the top.
Release a car. Watch it roll. Pick it up and release it again.
A 2-year-old will release the same car a hundred times โ the wheels rotating is the whole point. A 4-year-old will run heats, predict winners, change the angle to make it steeper.
Switch the ramp surface (book vs cookie sheet vs cardboard). Race two cars side by side. Add a tunnel at the bottom (a paper-towel tube).