The energy concept is fine, but I would suggest that there be ways to refill it without spending money. Such as if you win the duel then your energy is returned 75-100% and if you lose then you lose the energy you put in. Also I would suggest there be more multiplayer duels available per day. I do not want to waste points to simply duel people. It was good that you did not make the multiplayer duels cost energy, but...5 duels. Come now my friend. This is an awesome concept, but I think you need to change a few concepts to make it more likely for players to play longer than 30-40 minutes each day.
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