
ok ... some basic understanding ...
If ur attack power is less than the def of the monster then u will do 0 damage ... and i'm not talkin bout strength but ur over all attack power and when i say defence of the monster i don't mean it's dex but over all defence ... and in case u haven't noticed some creeps wear armor.
Then u have to take into account the element of the monster ur attacking... lets say it's a fire element monster and it's fire def is 10 and u fire attack is 30 ...then u should do 20 fire damage + full damage of all ur other ele attack. Again if the ele defence is more than ur ele attack u do 0 dmg.
And for all those who are thinking the values go into negatives cause their def is more ... have to be kiddin me ... cause if it goes into negatives then u'll actually be givin the creep health wid each attack and that is just

Ok let me explain with an example ...
lets say my stats are 500 attack power with 30 fire attack, 20 ice attack and 10 lightning attack.
Now i attack a monster wid 300 normal def and 10 fire def ...
My damage should be ..
(500-300) + (30-10) + (20-0) + (10-0) = 250 dmg
200 + 20 + 20 + 10
lets say i attack a monster with 600 def and 30 ice def
the damage should be ..
(500-600) + (30-0) + (20-30) + (10-0) = 40 dmg
0 + 30 + 0 + 10
And if ur thinking what happens when u have buffs on... well the same thing just add the extra damage to it and if u reduce the def of the monster it's the same thing all over again.
Hope this helps and u can't possibly have any questions bout this ... but if u do plz post it here and i will answer them for you.