BTW, the tournament system is broken. Attackers card don't tick down first turn, so the 'first turn' advantage is given to the defender, on top of being able to see the attacker's card and counter appropiately.
The energy system, as it stands, needs re-working.
You can only play for about 10 min before you have to stop, which is infuriating.
However, the energy system is an essential part of the game. It makes it so players can't retry levels until they win, so losing actually hurts you (it takes 15-20 secs to play through on 4x). Level spamming until until you win would take out all strategy and feel of accomplishment.
Energy should be depleted only if you lose, and max energy should be lower, like about 50. This would make it so skilled players can play for maybe an hour or more, but if you lose a couple times, you have to take a break.
+ this so the devs see