What’s there to misunderstand? Two stacks converge in an attack (or rather, one attacks the other). All regular creatures behave like creatures – they clash swords and strike each other. But there are unusual creatures that prefer to strike first; they are very swift, and their attack cannot be blocked, so regular creatures can only retaliate. And if two stacks of swift creatures meet, they attack each other simultaneously. It’s simple. The classic “strike-retaliate” system, on the other hand, seems more unnatural. This was definitely an improvement.