oohh I absolutely love this!! It's such a silly idea and executed very well!
The visuals are absolute top notch, I love the Earthbound-style battle backgrounds and the designs of the various trash/dirt creatures that you encounter. Everything is extremely well drawn and pleasant to look at. I also love how every creature has its own Undertale-style attack pattern that you can learn how to respond to. The music and sound design is also excellent!!
I think my biggest nitpick is that the timer going offscreen during battles feels a bit weird, because makes it a little unclear what's happening when you take damage or touch green (I thought I had an invisible health meter at first). It feels like information that *should* be available during the battle. The way you can see the bottoms of the numbers changing looks more like a glitch than something intentional.
I also found the green pickups to be a little inconsistent, something I felt like I touched them but they just go through me, and it's not clear why it sometimes works and sometimes doesn't. Also the arrow buttons for rotating the car seem to be going the opposite way to how my brain expects them to be.
Overall this game is extremely well made!! Excellent work!!