There has been recent articles on gamasutra about how easy it is to apply MMORPG-like leveling and "candy reward" and have immediate addictiveness. This game is another example :
While the gameplay is almost inexistant (you choose an opponent, you see an automated fight sequence, you win or lose), it's very addictive due to the new weapons/technics/pets you can get when winning a fight and the fact that while the fights are completely automated, the is a lot of depth in them, with lots of different technics/items. For example, in melee fight, you can dodge, counter-attack, steal your opponent's weapon, disarm your opponent, throw you weapon and there are probably lots of other technics (I'm only level 4...). The fights are always different and interresting to watch, especially since you're limited to 3 fights per day.
Kukkatytto stealing my bludgeon before crushing me...