Implement shared 7-bag piece sequence

- Add generatePieceBag() and createPieceQueue() for 7-bag system
- Add pieceQueue and playerSequenceIndex to lobby state
- Modify spawnPiece() to consume from shared queue per player
- Update player-hold handler to manage sequence index on hold
- Add sequenceIndex to state updates for tracking
- Update client loadState() to receive sequenceIndex

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

public/js/game.js

@@ -366,6 +366,7 @@ class TetrisGame {
     this.level = state.level;
     this.gameOver = state.gameOver;
     this.eliminated = state.eliminated;
+    this.sequenceIndex = state.sequenceIndex || 0;
     this.dropInterval = Math.max(100, 1000 - (this.level - 1) * 100);
   }
 }

server/index.js

@@ -15,7 +15,9 @@ const lobby = {
   players: new Map(),
   spectators: new Map(),
   gameStarted: false,
-  gameInterval: null
+  gameInterval: null,
+  pieceQueue: [],
+  playerSequenceIndex: new Map()
 };
 
 const PORT = process.env.PORT || 3000;
@@ -37,6 +39,36 @@ const BOARD_HEIGHT = 20;
 const GARBAGE_COLOR = '#666666';
 const LOBBY_ROOM = 'global-lobby';
 
+// 7-bag piece generation system
+function generatePieceBag() {
+  const bag = [...TETROMINO_KEYS];
+  // Fisher-Yates shuffle
+  for (let i = bag.length - 1; i > 0; i--) {
+    const j = Math.floor(Math.random() * (i + 1));
+    [bag[i], bag[j]] = [bag[j], bag[i]];
+  }
+  return bag;
+}
+
+function createPieceQueue(bagCount = 14) {
+  let queue = [];
+  for (let i = 0; i < bagCount; i++) {
+    queue = queue.concat(generatePieceBag());
+  }
+  return queue;
+}
+
+function getPieceFromType(pieceType) {
+  const tetromino = TETROMINOS[pieceType];
+  return {
+    type: pieceType,
+    shape: JSON.parse(JSON.stringify(tetromino.shape)),
+    color: tetromino.color,
+    x: Math.floor(BOARD_WIDTH / 2) - Math.floor(tetromino.shape[0].length / 2),
+    y: 0
+  };
+}
+
 io.on('connection', (socket) => {
   console.log('Player connected:', socket.id);
 
@@ -206,16 +238,31 @@ io.on('connection', (socket) => {
     if (!player.canHold) return;
 
     if (player.holdPiece === null) {
-      // First hold - store current piece and spawn next
+      // First hold - store current piece and get next from queue
       player.holdPiece = {
         type: player.currentPiece.type,
         shape: JSON.parse(JSON.stringify(player.currentPiece.shape)),
         color: player.currentPiece.color
       };
       player.currentPiece = player.nextPiece;
-      player.nextPiece = getRandomPiece();
+
+      // Advance sequence index since we consumed nextPiece
+      const idx = lobby.playerSequenceIndex.get(playerId);
+      lobby.playerSequenceIndex.set(playerId, idx + 1);
+
+      // Get new next piece from queue
+      const nextType = lobby.pieceQueue[idx];
+      if (nextType) {
+        player.nextPiece = getPieceFromType(nextType);
       } else {
-      // Swap with held piece
+        // Regenerate queue if exhausted
+        lobby.pieceQueue = createPieceQueue(14);
+        player.nextPiece = getPieceFromType(lobby.pieceQueue[0]);
+        lobby.playerSequenceIndex.set(playerId, 1);
+      }
+    } else {
+      // Swap with held piece - current piece goes to hold, held piece becomes current
+      // Don't advance sequence - the current piece is just going into hold
       const temp = {
         type: player.currentPiece.type,
         shape: JSON.parse(JSON.stringify(player.currentPiece.shape)),
@@ -228,6 +275,15 @@ io.on('connection', (socket) => {
         y: 0
       };
       player.holdPiece = temp;
+
+      // Update nextPiece to be the piece that was just held
+      player.nextPiece = {
+        type: temp.type,
+        shape: JSON.parse(JSON.stringify(temp.shape)),
+        color: temp.color,
+        x: Math.floor(BOARD_WIDTH / 2) - Math.floor(temp.shape[0].length / 2),
+        y: 0
+      };
     }
 
     player.canHold = false;
@@ -325,8 +381,22 @@ function getRandomPiece() {
 }
 
 function spawnPiece(player) {
+  const idx = lobby.playerSequenceIndex.get(player.id);
+  const pieceType = lobby.pieceQueue[idx];
+
+  if (!pieceType) {
+    // Regenerate queue if exhausted
+    lobby.pieceQueue = createPieceQueue(14);
+    lobby.playerSequenceIndex.set(player.id, 0);
+    return spawnPiece(player);
+  }
+
+  // Advance sequence index for next spawn
+  lobby.playerSequenceIndex.set(player.id, idx + 1);
+
   player.currentPiece = player.nextPiece;
-  player.nextPiece = getRandomPiece();
+  player.nextPiece = getPieceFromType(pieceType);
+
   if (!player.currentPiece) return false;
   return isValidPosition(player.currentPiece, player.currentPiece.x, player.currentPiece.y, player.board);
 }
@@ -419,6 +489,15 @@ function getGhostY(piece, board) {
 function startGame() {
   lobby.gameStarted = true;
 
+  // Initialize shared piece queue
+  lobby.pieceQueue = createPieceQueue(14); // 98 pieces (~14 bags)
+
+  // Initialize sequence index for each player
+  lobby.playerSequenceIndex.clear();
+  for (const player of lobby.players.values()) {
+    lobby.playerSequenceIndex.set(player.id, 0);
+  }
+
   for (const player of lobby.players.values()) {
     player.board = createEmptyBoard();
     player.score = 0;
@@ -476,7 +555,8 @@ function getStates() {
     score: p.score,
     lines: p.lines,
     level: p.level,
-    eliminated: p.eliminated
+    eliminated: p.eliminated,
+    sequenceIndex: lobby.playerSequenceIndex.get(p.id) || 0
   }));
 }