UI needs some work, and keyboard shortcuts sometimes seem not to work. For example, I press m to move, and the item is removed from the UI. Perhaps consider adding a check list for players as well to let them know the minimum expected part list. 

The UI needs some work, button placement is a bit weird, the drive/start buttons should be positioned at center or bottom instead of the top, same for the next page buttons of the help pages. Controlling the car via keyboard would be a good addition too. Other than that, the gameplay feels a bit too hard, with cars breaking apart too easily.

I really like the idea - like Hill Climb Racing meets Death Stranding. 

I couldn't really figure out how to play. My car wouldn't drive in certain environments, and I couldn't understand what the objectives were with different items.  The controls also didn't feel intuitive; clicking to go or stop felt weird, and I didn't understand where the engine comes into play.

I like the idea a lot and I see the potential here, I would just need the game to be a little clearer.

Cool concept. Looks good, and it's easy to understand how to play. I liked the variety of levels and parts. I just think it's a bit too hardcore from the very beginnig - I've built three cars but none of them was able to move :) Probably some interactive (step by step) tutorial would be nice.

Overall it's interesting and really promising.