Great sounds! I'm liking the neon sci-fi vibes.
Having a slow down mode to make it easier to hit the rings when going fast is a good idea!
The visuals do start to break at higher speeds, with bigger and bigger gaps between the buildings. Don't know if this is intentional or not.
If you want to keep it a webbuild, consider changing the aspect ratio to be smaller so it fits better in the browser - I've found unity webbuilds to run terribly in fullscreen mode, but run a little bit better when just using a built in player (but the size needs to fit, like a standard 1028x720). This is something that Unity just struggles with.