Interesting idea, but seems hard to program. Especially because playing a shield would mess with the opponent's damage. Also, it seems like it could become OP with acceleration, overdrive, and Gravity force.
Not hard to program at all. The game already does it! Ever see the little yellow splash on your health? That's the calculation for your damage. The same needs to be applied to this card, is all!
Gravity Force and Overdrive are other problems... Perhaps Immaterial? After all, if you take 0 damage, this card dies. Damage vs. Dead dog gives a whole new strategy.
The problem is that stuff of your "next turn". What if your opponent plays a Sundial next turn? No way to know it (unless you're at PvP1 with an opponent without cards in its hand nor Time Quanta).
Whatever, you could take in account the yellow bar, but it works horribly bad. It doesn't take in account Momentum, "Miss" Shields (Phase/Dimmensional/Dusk Mantle/Fog Shield/Bonewall), Adrenaline nor Antimattered creatures. I think that should be fixed before this can come to reality.
All in all, I like the ability, but dunno how it would be useful. May need some help in imagining one possible scenario of its use.
