I understand that the key in this games design was simplicity but I still think it's more simple then it should be. It should at least have a save feature, becouse it's very long to play trough in one sit!
Also I think it's way too easy. (And I rarely complain about easy difficoulty, I hate hard games!) There is no chellenge, every monster falls easily, even the bosses (in fact they die easyer than normal monsters!) you rarely get hit at all and there are plenty of healing items anyway.
In all this simplicity the battles are still too complex: the fights could be automated becouse you only need to use the normal attack, the rest are useless. The 'reckless strike' is not only useless, it's also dangerous becouse with that it's almost garanteed that you get hit.
It's not explained what the unlockable armores do if they do anything at all. However even if they are just eye candies there either should be more of them or the diamonds should be more scarce becouse I unlocked the first two right on the first level and the last one on the second level and then the lots of diamonds I found were useless.