Mana Manipulator

Whenever you cast an instant or sorcery spell,
reduce the cost for the next instant or sorcery
spell you control by the amount of instant
and/or sorcery spells you cast before in this turn.
Whenever your opponent casts an instant or
sorcery spell, increase the cost for the next
instant or sorcery spell your opponent controls
by the amount of instant and/or sorcery spells
your opponent cast before in this turn.