The door and the reveal
On the day, the wall turns from a gathering into a gift. The person it is for presses one pill and every square turns over for them.
Before it opens
Until the time, their link shows the wall face down, each square with the name of who added it, and a countdown. They can see who is there. They cannot see what anyone made.
The door
At the time, the wall dims and one line appears: Everyone's here. Under it, a black pill, Open it. Nothing happens until they press it, so they can wait for a quiet minute, or for the people in the room.
The reveal
Pressing Open it turns the squares over one by one, from the centre outward, then the rest together. The last one flies to the middle and opens. Tapping the wall makes it go faster, a fourth tap skips to the end, and holding a press pauses it. It is never slower than they want.
The end
When they close the last square, everything goes still for a moment, with nothing on screen but the wall. Then a card comes up in the middle: That's everyone., with how many people are on the wall.
On their device the pill under it is Say thanks to everyone, which opens one square for everyone on the wall. Anyone else who watched the reveal sees Replay there instead. Tapping or pressing anywhere else puts the card away.
After that, the wall is theirs to wander. They open any square and reply to it: one of the four emoji under its name, and a line or a voice note if they like. Their emoji sits on the square's corner and their words or voice opposite the name, for everyone with the link.
Reactions, once it has opened
From the moment the wall opens, anyone with its link can react to a square too: open it and tap one of the four emoji under the name. Each has its number beside it, so everyone sees how many hearts a square has. Tap another to change yours, or tap yours again to take it back; each device has one per square.
 The person the wall is for uses the same row, and their pick counts as well as being their reply. On your page for the wall, Most reacted puts the squares with the most first.
Opening it now
Want it open before the time, for a party that moved or a day that came early? On your page for the wall, press Open it now. A card says what happens: the person it is for will see every square the moment you press it. It can't be unopened. Press Open it, and their link goes to the door straight away.
Replaying it
On the device that opened the wall, the pill card top-left has Replay the reveal for 30 days. Other devices see the wall as it is. The person who made the wall can replay it too, from their page for the wall.
If it did not play
Opening the link on a second device after the door was pressed goes straight to the open wall. If the first device lost its connection part way, opening the link again shows the open wall, and Replay plays it from the start.