Thread:Hikari 93/@comment-22439-20131228195745/@comment-11454852-20131229143840

@Nixie17

When you attack a monster you compare your ATK and the opponent's DEF, if your power is higher or equal, you destroy the monster but don't do any damage

To deal damage, you must attack the opponent directly, which you can only do when the opponent's center is free, or you have a monster/item with Penetrate.

In general, you have to get rid of the center monster before dealing damage, so its recommended to have a hard to beat monster defending you. Check the Gameplay page for the whole rulings.