Keep the big blind moving one player at a time when somebody leaves out of the blinds

Passing the button to the next player is right until a chair between the button and
the blinds empties. Then it pulls the whole blind order forward a place. Measured,
four-handed, button on Ben, blinds Cal and Dee, with Cal cashing out:

    tool:    button Dee, small blind Ann, big blind Ben
    correct: dead button on Cal's chair, small blind Dee, big blind Ann

Ann is never asked for the big blind she owes, and Ben pays one a full orbit early.
That is a real big blind out of a real stack, and it happens every time somebody
stands up out of the blinds — which in a cash game is constantly. It is also the
kind of thing the dealer gets blamed for, because the tool is the thing everyone at
the table is reading position off.

The dead button rule holds the rotation to the seats for one hand instead of to the
players. The button follows the small blind round, which at a table with nobody
missing is the same next-player-along it always was; when that player has gone the
button rests on their empty chair for a hand, and when the big blind has gone no
small blind is posted. Either way the big blind advances exactly one player, which
is the whole point of it.

Worked out from who actually posted last hand rather than from the seating as it
stands, because by the time the question is asked the people it turns on are the
ones who have left. Heads-up is exempt — the button is the small blind there and
there is no position to leave dead — as is a table too sparse to have a rotation to
hold to, and a dealer who moves the button or names a blind by hand overrules it.

Both dead positions are said out loud rather than left to look like a fault: the
deal prompt explains them in a sentence, and the dead button goes hollow and dashed
so the felt agrees with the words.

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_015bnp7xKUPFFSpwkYNFaPgb

JoshHeaps.Net/wwwroot/js/casino/holdem/actionBar.js

@@ -601,12 +601,27 @@ const ActionBar = {
             return wrap;
         }
 
-        line.textContent =
-            `${name(preview.sbIndex)} posts ${Money.format(preview.smallBlind)}, ` +
-            `${name(preview.bbIndex)} posts ${Money.format(preview.bigBlind)}` +
-            `${preview.headsUp ? " · heads-up" : ""}${preview.manual ? " · blinds set by hand" : ""}`;
+        // A dead small blind is a hand with only one blind in it. Saying "nobody posts
+        // the small blind" out loud is the whole point — a dealer who reads a preview
+        // with a blind missing and isn't told why will assume the tool has lost track.
+        line.textContent = preview.deadSmallBlind
+            ? `No small blind this hand, ${name(preview.bbIndex)} posts ${Money.format(preview.bigBlind)}`
+            : `${name(preview.sbIndex)} posts ${Money.format(preview.smallBlind)}, ` +
+              `${name(preview.bbIndex)} posts ${Money.format(preview.bigBlind)}` +
+              `${preview.headsUp ? " · heads-up" : ""}${preview.manual ? " · blinds set by hand" : ""}`;
         wrap.appendChild(line);
 
+        // Why a position is missing. Both of these are the dead button rule doing its
+        // job, and both look like a bug until somebody says otherwise.
+        if (preview.deadButton || preview.deadSmallBlind) {
+            const dead = document.createElement("p");
+            dead.className = "dealPromptLine dealPromptAside";
+            dead.textContent = preview.deadButton
+                ? `Dead button — seat ${preview.buttonIndex + 1} is empty. Its player left out of the blinds, so the button waits a hand rather than moving the big blind on twice.`
+                : `Dead small blind — the player due to post it left the table. The big blind still moves on one player, so nobody pays two in an orbit.`;
+            wrap.appendChild(dead);
+        }
+
         // Dealing relocates a button sitting on an empty chair. That has to be said
         // before it happens rather than discovered afterwards — a fresh table starts
         // the button on seat 1 whether or not anyone is sitting there.