First of all, why does everything have a shadow that gets projected onto the backdrop? It makes the game feel less like we're in space and more like there's a big wall behind us. Also, I feel like the player moves too slowly, making it very difficult to judge when to jump over spikes. Maybe it's just the fact that as your player moves right or left he also moves down due to the curvature of the planets. It took a second, but not long after I started playing I got used to this.
These are minor complaints. The game is impressive for only being made in 48 hours and by no means do I dislike it. It's a great game, with creative ideas and a nice and simple (but not unoriginal) concept.
One last thing: when you're at the bottom of planets pressing the right arrow key you will move left, and vice versa. I guess this is necessary and it adds extra difficulty to the game, but it's tedious nevertheless.