Bblflitt, the Gossamer Mouse

Bblflitt is blue and green and enters the
battlefield with a flying counter or a trample
counter on it and a +1/+1 counter for each
mana spent to cast it.
Commander tax for Bblflitt is only {1} instead of
{2}. Whenever you successfully cast Bblflitt from
your command zone for the first time each turn,
if it costed 21 or more mana to cast, you win the
game at the beginning of your next turn.