Counterbalance
{U}{U}
Enchantment
Oracle Text
Whenever an opponent casts a spell, you may reveal the top card of your library. If you do, counter that spell if it has the same mana value as the revealed card.
Watch Out
Cast trigger fires even if counteredWatch Out
This triggers when the spell is cast, before it resolves. Even if the spell is countered, the cast trigger still resolves. Copies of spells are not cast, so they won't trigger this.