I love this game, very easy to pick up and play. I agree with other comments that if you haven't played a similar game before it can be hard to tell what to do, but I just assumed 'Tiny Wings' style logic would work and I was having fun in no time. I'd suggest something more obvious as a tutorial, like forcing the player to start moving by holding in the 'A' button and having text on the screen telling him/her so. It's not obvious to a player whose never played something similar how increasing gravity at the right times increases your speed downhill but at the wrong times forces you into the back side of hills and kills speed.
Thanks for trying out my game, glad to hear that you are enjoing it. 'Tiny Wings' was my main inspiration for the game, but if you haven't played it before I can see why people are stuggeling with understanding Hillslide. I'm working on making a interactive tutorial, wich will hopefully make it easier to pick up for new players.