Drive with the arrow keys: the grass slows you down and the coins go round the track.
There is no 3D here. The track is one flat picture on one full-screen sprite, and its material does the SNES's maths per pixel: each row below the horizon is a line of floor at height / rows below the horizon, turned by the camera's angle.
The trees and coins are ordinary sprites put through the same maths in reverse, on the CPU. Every picture is drawn by the example on a canvas and loaded as a data URL: nothing to download.