Pretty nice
There were a few bugs, but what I thought worst was the unbalanced difficulty. The first levels - 2 and 3 especially - are hard, because you have to go through the nasty sand (the hardest type of ground clearly) and the river, but then it's the forest and three levels that you can do entirely on grass. By then, you're already used to jumping and kicking the rats and the ninjas, so these levels are much easier than the first ones. They can be beaten without a single shuriken. Also, the dragons seem to get faster, which makes them easier to kill (the fireballs are more spaced). Holes 8 and 9 were more challenging, forcing you to go through different types of ground, sand and water included. However, by then I had a huge stock of shurikens so I only had to kill every enemy before it approached or shot something. Dragons 8 and 9 were good, too - 8 was slow enough for it to be almost impossible to escape the fireballs and 9 was fast enough to be moderately hard to hit.