i won't say it's "impossible" to handle, but the car's a bit too fast imo.
between you bouncing around whenever you so much as touch a wall, and sometimes getting stuck to it when you're directly facing it, it's really difficult to control.
apparently you can get all the additional goals without having to clear the corresponding level;
as long as you at least collect it, it counts as having "reached the goal".
this is especially relevant for levels 13 and 15, which i cannot clear for the life of me.
add to that level 18, though thankfully that one doesn't have a collectible.
i can confirm it's at the very least possible to clear all the other levels, with my worst one being level 12 (which according to the game took me 120 retries). it's especially evil because the starting section is hard enough, but then you get to pick-a-path and if you die you have to redo the first section.
i can't even say this is the hardest level because at least i've cleared it, which can't be said for 13, 15 and 18.
i don't see anyone clearing every single level with 0 deaths anytime soon.
additionally, the number of deaths in every level seems to auto-reset when you refresh the page.
because there's no clear indication of a level being cleared, i'm going to assume the game does not save progress between sessions (rather than "auto-resetting" for whatever reason. same result), meaning you'd have to do everything in a single sitting
EDIT: ok level 18 specifically seems like a gimmick level, in the sense that you can just decide NOT to play it and it will send you to the next level instead. not sure if i like that idea but i'm not complaining about one less level to worry about. i guess 13 and 15 are the real rough ones.
while i'm still here, i would like to report a bug i guess? apparently in levels where there are moving red blocks (specifically ones that go off-screen), the blocks tend to "persist" if you die.
when you restart the level, you'll get the ones from the normal cycle, and an extra one from the previous cycle.
it's nothing game-breaking since it only happens on the first cycle every reset, so you can just wait it out, but i just wanted to mention it
EDIT 2: gave it another try. as usual, level knowledge makes all the difference.
i managed to clear every level with less than 20 deaths (with the exception of level 13, which took me 127 by itself).
might see myself coming back to this and giving it another try in the near future. i just need to figure out how to actually take that corner on level 13 properly (also 6 and 15. those are really rough)
EDIT 3: managed to clear every level with 0 deaths except level 13 (my current best is 113). guess i just gotta bash my head against it until i figure it out
EDIT 4: i figured it out.
for future reference, i took the short way (the one that doesn't pass through the green goal):
the only way to get a tight enough turn without sliding off into a lava wall is to go face-first into the short side of the rectangular solid wall and keep turning.
if done correctly, your car will get "stuck" close to the wall as you turn.
if you don't bump into anything you can still get past the corner but when making the U-turn your car will swing towards the lava wall on the bottom, so i don't see another way to make it besides this gimmick