Not very good
I didn't like it that much. I would like to see more movement of the character, instead of him only moving his feet. It also could be improved if you made more variation in the level design. I also found a glitch: you can stand im the chinese guys in the first level without getting hit. But the most important thing that can be improved is the jumping. I quitted this game because of that. The jump system is programmed that if you are on the edge of the platform, the yak doesn't jump but instead falls straight into the pits, and if you are too far away, you don't make it, and you jump into the pits too. Because of that I often miss the first or the second jump in the first level. What irritates me too is that you can't defeat the enemies. Come on, a yak who gets killed by a seagull. That's not fair. So make it possible to jump on it, kick it, at least there must be something you can do. And the bosses are boring too. At least the first one is. I mean, stand in the middle and jump over the samurai 30 times, and then he kills himself. What's the fun of that? Again, make it possible to jump on him. Also, make continues. That way, you can retry a level more times, so your chances of survival for the next time are higher. For example: After I was game over due to the eskimo hehind the ice pillar in the second level, I knew he was there. But then I needed to complete the first boring but glitchy level again, before I was able to get there again. And I didn't want to do that all again.
The positive points are that the yak is cute and that the music fits well. But the game has too much glithches to be entertaining. I'm sorry.