Thanks for trying the game! And your comments.
It was my second 'attempt' at a game for the contest (jam). Cutting some corners was part of the process.
There's a collision with the cars but the player is directly put at x=0 at all times. I indeed made it so the player needs to jump on a car to reach a coin. After standing on a car, a second (higher) jump can be made, to reach the coin. The coin needs to be touched with the belly of the pig (since he has short hands, ofcourse). You can also jump from car to car (and schoolbus, and truck...). No doubt you will get the hang of it after a few times trying.
Keep an eye on the truck on the right, at some point it will be near the horizon. Look at what happens when 6 (or even 10) coins are collected.