Similar to LukasWho, I found it frustratingly hard to get anywhere (couldn't really), and I wasn't sure what I was meant to do.
My guess was to avoid dropping the boxes with reckless driving, while dodging (or hitting?) the red thing in the distance; but I could never get close enough.
I also encountered what I think is a bug where, after playing a few times, I was unable to play anywhere because as soon as I started to drive I would instantly fail.
No box fell off, and the time limit was nowhere near empty - literally just started.
If I may offer meta-feedback, this felt similar to me to your GMTK jam game from last year.
I actually found the mouse chase very hard and frustrating, until I read a comment talking about how quickly it could be finished.
That caused me to figure out that it was "easy", as long as you played optimally for the first few seconds; but, if you missed those first few seconds, it was basically impossible to catch up to the mouse.
I bring this up because in both cases I get the impression that you think the games aren't hard.
I suspect that you, as the developer, are testing these games by playing them in some optimal way that makes you blind to how hard they are for someone who doesn't know how to do that.
Something to keep in mind for future games, perhaps.
Anyway, on the positive side, I think it looked very pretty, and I really liked that I could stack the boxes myself before driving off.
The added layer of "stacking skill" on top of "driving skill" made it more interesting than if you just had to drive with pre-stacked boxes.
I think an easy way to make this game more fun would be to invert the time limit punishment into a speed run reward.
i.e.
Just use boxes falling as the fail condition.
Count *up*, instead of down, and report "best times" on an end screen to encourage the player to try and do it faster next time.