Who sees what, and when

Before a wall opens, the person it is for sees who is on it, never what. After it opens, everyone with the link sees every square.

The person it is for

Maya has her own link. Until the time you set, it shows the wall face down: every square a plain back with the name of the person who added it, and a countdown at the foot. She can watch the names arrive. She cannot open a square, and she never sees a number, only names.

That is why Maya only sees names. Her link is locked until the moment, on purpose, so the words, photos and voices land all at once when she opens it.

The people adding

Everyone else uses the wall's own link. It shows the wall as it is, so the people adding can see what others made and know what is enough. Send Maya's link only to Maya, and the shared link only to everyone else.

You

You see what everyone sees on the shared link, plus your page for the wall: who has added, who has not, and the controls. Some walls are set so that even you wait for the moment; then your squares stay face down for you too.

After it opens

The wall stays at its link for good. Maya sees every square and can reply to each one. The people who added see her replies under their squares. Nobody else finds the wall: it is never listed or searched, and only people with the link reach it.