There was so many times I thought "ooh that's clever!" here!
Using the countdown as the healthbar, and for the money, and showing the past you so you can see how much faster you're going, and having the shop be a physical space just left of the start, not to mention a bunch of the upgrades, all of it is very well thought out!
Also love the humor of the shopkeep, and how clean the animation for the speech bubble is!?!
But yeah, all around very well done! :)