Thartax, Mind Delver

Whenever Thartax, Mind Delver enters the battlefield, draw X cards, where X is the number of creatures you control.
As long as you have 4 or more cards in your hand, Thartax, Mind Delver gets +0/+5.
As long as you have 4 or less cards in your hand, Thartax, Mind Delver gets +4/+0.