Really cool game :)
After long time I started Unity too and started work on car game (was not really sure what I wanted to achieve) - then I found your youtube channel :) Lot of inspiration :) then I found out it is not finalized yet so I each time waiting for new "episode" :)
My game is now on similar stage but it is visible that I do not have such experience in modeling as you do :) (but I'm better software developer :) ). I like your low poly style.
And I think I did checkpoints better :) at least what I miss in your game that are visible checkpoints and indication if you did go through it.
Good luck and really thanks for your videos...