Considering this is your first flash I find this a rather decent one.
But here are some things you might consider changing.
- Background: Add one, now it feels so empty.
- Explosion: Not nearly the blast of a real creeper!
- Sound: The explosion is rather weak sound-wise as well.
- The ending: the "trolololol" music feels out of place and unnecessary
- Buttons: Play buttons are an animators friend.
Anyways keep working hard on improving!