It's hard.
This was a good game that had me going for several minutes. The graphics felt very retro and this added to the game value. The music had a nice groove, even though there were only two tracks and these two tracks didn't fit the game-play. The game-play itself was smooth and mostly solid. The only things that bugged me were :
1) The frog suit jumps higher, and is your only hope of beating a level in the expansion
2) The weirdest ice-movement I've ever seen in my entire life. (I'm actually quite surprised nobody mentioned it, maybe it's just my computer?) When on ice, you slide in the direction your facing. Even when you landed straight on top of it and not a single button is pressed. This is really annoying and causes 30 percent of my frustration.
These are nothing but annoying stuff from being a great game instead of just a good one.