gistfile1.cs

class SanguineBond : CastableCard, IEnchantment, IEventHandler<PlayerLifeChanged> 
{ 
	public SanguineBond()
	{
		Name = "Sanguine Bond";
		ManaCost = Manacost.Create(black: 4, collorless: 2);
		Description = "Whenever you gain life, target opponent loses that much life.";
	}
	
	public void Handle(PlayerLifeChanged @event)
	{
		if (@event.Delta > 0 && @event.Player == CardOwner)
		{
			var target = Engine.SelectOpponent();
			target.TakeDamage(@event.Delta);
		}
	}
}