Hi! You've got a really solid concept here — driving a car in circles and smashing zombies. Here's what I'd like to see in the game.
Overall, it's a good concept, the cards are clear, the game loop is understandable. What's not clear yet is the purpose of killing zombies. What's the end goal? What's the point of running them over with the car? It's obviously just for fun, but the player needs at least some minimal goal so it's clear why you'd upgrade the car and kill zombies. In other words, you need some kind of kill counter, or unlocking a new location the player can drive to, or something along those lines.
Of course, I'd love to see better physics, so the car's appearance changes with every upgrade. I'd also like clearer physics with knockback, so zombies can go flying — that would make it feel way more epic.
Here's an important issue: I held down "forward" and "right," or "forward" and "left," and I basically just drove in a circle the whole time, with nothing stopping me from abusing that. So the way zombies approach the car needs to be adapted somehow, so they come at you from different sides and you can't exploit this mechanic.
Other than that, it's great — keep going, keep upgrading the game. You're on the right track, really strong concept.