Avacyn, the Returned Form

Whenever an human enters the battlefield under your control, put a charge Counter on Avacyn, the Returned Form.
Whenever an angel enters the battlefield under your control, put 3 charge Counters on Avacyn, returned form.
Remove 10 charge counters: Put a +1/+1 counter on each creature you control.
Remove 15 charge counters: Create a 3/3 angel token with flying.
Remove 30 charge counters: Flip Avacyn, the Returned Form.