General
Fun little arcade game but I was missing a challenge or a goal to achieve. Other than that I managed to get 150+ score and then I got intrigued to see what would happen if I crashed myself into a rock. I was not disappointed :)
Also nice to read that you learned something new! I hope those new learned skills will help you in future projects!
Theme
I think it fitted the theme well. I got an arcade / old school game vibe which is what you were going for (I hope I am not wrong saying that :P )
Audio
I liked the background audio and props to you for making it yourself! Maybe for future projects add a way to control the audio? Even if you start with a simple mute function. That way if someone would like to control it they have a way to it ;)
Graphics
Nice! love the pixel art at first I thought it would be hard to see the difference between the background and the objects in front since there is not much contrast but by surprise for me it was just right enough.