Forum:Question about cloudians

My friend just used rain storm on a Cloudian - smoke ball, and he chose to drop the attack by 2000 to destroy 2 spell or trap cards. My question is, can he drop his monster's attack below 0, and if not, can he use still the card to destroy my cards without dropping the monster attack all the way? what should happen in this situation? 173.169.250.73 (talk) 00:10, January 26, 2012 (UTC)