It is, however, a complex product, difficult to understand and play, with a very steep difficulty curve. (metacritic.com)
This game has a fairly steep difficulty curve, you'll know it when you hit it, but it is something you can get through if you set your mind to it. (heavy.com)
There's a pretty steep difficulty curve here which is going to test even the most experienced of speed racers. (fingerguns.net)