The concept is really great and I really enjoyed the implementation. The game was perhaps a little difficult for me (I managed to get as far as level 5, I don't know how far the game goes).
Anyway, the visuals are great, and this idea of the little slime facing hordes of adventurers in search of XP is a fantastic idea. The delay between jumping and attacking is also very well done, giving the impression of being a fragile little slime struggling to survive in the face of armor and swords!
Bravo!