How could the sixers enter the gate?

Question

At the end of the book

Parzival is able to enter the 3rd gate after all the other avatars have been killed by the Catalyst. The Catalyst also destroyed castle Anorak leaving the 3rd gate hanging in mid-air. Once Parzival entered the 3rd gate, the gate closed.
Since the castle was destroyed, how could the sixers use their keys to open the 3rd gate without keyholes to insert keys? The castle was gone, walls were gone, no doors, no keyholes, nothing.

In chapter 36 When they disclose to Parzival that the sixers have entered the gate. Art3mis tells Parzival “The gate closed after you went in, but when the sixers arrived they used three of their own keys to reopen the gate.”

Answer 1

The Gate is left suspended in the air on its own. It has to still be there for Parzival to fly up to it and enter it himself. The Sixers just have to show up with a flying convertible, or something with a big door, hover alongside and present three copies of the Crystal Key.

It's never really made clear what happens to a gate after someone enters it, because our view point protagonist has passed through, but presumably it defaults back to it's previous closed state.

---

I've been back and checked the relevant passages. Chapter 36 is when Wade enters the 3rd gate, it's explicitly mentioned as floating above him.

I glanced back up at the open gate, suspended in the air above me, so far out of reach.

The sections about gates I and II talk about the gates disappearing after they gate is cleared. Which means they might just sit there open while someone is inside.

Chapter 11 Copper Gate I jumped through the exit and landed with a thud on the floor of Halliday's bedroom. When I turned around and looked at the wall, I saw the gate was now gone and the WarGames poster had reappeared in its place.

Chapter 27 Jade Gate When I emerged from the gate, my avatar reappeared back inside Tyrell's office. The Voight-Kampff machine had reappeared in its original location, resting on the table behind me.

There's a key difference between the Crystal Gate and the other two though. Both the Copper and Jade gates required you to do something to make them appear, whereas the Crystal Gate just needed you to get into the castle. Adding that to the live competition aspect of the 3rd gate, suggests it was just set up to ensure that as many avatars as possible could get in and attempt to clear it at the same time. The most important thing to remember is that there doesn't have to be any consistency, because it's a computer game and it does whatever its programmer wants it to do.

Answer 2

To answer the specific question

how could the sixers use their keys to open the 3rd gate without keyholes to insert keys?

If you think about a regular door, where are the keyholes, usually? In the handle or in the deadbolt - mounted to the face of the door. I never imagined anything different, and I don't remember any indication that

the keyholes were not directly on the face of the gate. Therefore, all the sixers had to do was fly up to the face of the gate somehow, and the keyholes would be there waiting.