The chain
When you play a spell it does not just happen. It goes on the chain, and the other player gets a say before it resolves.
The chain
resolves from the top
Empty. Nothing is waiting to resolve.
Remember
The chain resolves top down — last played, first to happen. Triggers go on it too, not just spells. And it is not settled once built: after every link resolves there is a fresh window to add another before the next one goes off.