im sorry but you did a terrible job at the challenge part. i loved the game up to level seven. i spent a good while on it, but i eventually got past it. then i got to stage 9, where i died 56 times. literally. then i just rage quit.
all in all good concept but bring the toughness down. 3/5
heres a good strategy once you get a large enough fuel tank just stay lw to the ground and use boost only when u have to. just rely on the wind it ups to get u there. i once got 2000 m like this. I swear