Introducing Synchronous Messages
A few years ago, I wanted to have a tool to enable the play of hidden information games (Rock-Paper-Scissors, Odds/Evens, etc), but there didn't seem to be one. Now I've made one, the Synchronous Messages (SM) system.
Longtime associates will recognize that this is not the first such thing I've created. I developed the similar Simultaneous Revealed Orders system a while back. It was discontinued for a good reason, but this serves the same role, and should do it better.
For a practical demonstration of how the SM system works, suppose that you have two players who want to play a RPS match. The first person goes to the page. He already has registered a SooperGrape account, so he needn't fill in the username (or password). The user count is already 2, so he doesn't need to change that. In fact, the only thing he needs to fill in is his first move - 'paper', which he puts in the text box.
After he hits the 'submit' button, the 'Messages' box on the right side of the screen will show the batch ID, along with other information. It will show him his move (which nobody else can see yet) and that there is one message left before the round of 2 messages is finished and all the messages are revealed. He copies the batch ID and gives it to his opponent. His opponent goes to the site, puts in a username and password, puts the batch ID in the batch box (so as to post to the same batch, instead of creating a new one), and plays her opening move - 'rock'. After submitting, she sees both moves and that she has just lost the first round of her game. And when the first player comes back from lunch, he can hit the 'submit' button, without entering any text, to refresh his view and see the activity that has taken place.
You can only have one pending message at a time, so if you attempt to send another one during the same round, it will edit/replace the one you already have. Similarly, the roster of users for a batch is determined when everyone sends their initial messages. Once two people have posted to a batch, they are the only ones who can use it. Other people can read the batch by typing in its ID, but they cannot post to it or edit the pending messages.
It is easier to use than it sounds like, and can be a lot of fun. I hope, Lord willing, that this can be a useful public service going forward.