I saw this game called Blastonaut featured on Appoday today and it's probably one of the hardest games i've ever played.
Picked from app store:
"Your shuttle blows up and sends you flying through the endless space with enormous speed. Collect oxygen tanks and powerful items while trying to dodge asteroids and travel as far as you can."
The game is free and you can download it via itunes: https://itunes.apple.com/us/app/blastonaut/id873643466?ls=1&mt=8