dynamic lobby sizes

src/client/GameModeSelector.ts

@@ -88,9 +88,12 @@ export class GameModeSelector extends LitElement {
     );
     this.requestUpdate();
 
-    const allGames = Object.values(lobbies.games ?? {}).flat();
+    const allGames =
+      lobbies.mode === "multi"
+        ? Object.values(lobbies.games).flat()
+        : [lobbies.lobby];
     for (const game of allGames) {
-      const mapType = game.gameConfig?.gameMap as GameMapType;
+      const mapType = game?.gameConfig?.gameMap as GameMapType;
       if (mapType && !this.mapAspectRatios.has(mapType)) {
         // New Map reference triggers Lit reactivity; placeholder ratio 1 lets
         // has() guard against duplicate in-flight fetches.
@@ -114,9 +117,15 @@ export class GameModeSelector extends LitElement {
   }
 
   render() {
-    const ffa = this.lobbies?.games?.["ffa"]?.[0];
-    const teams = this.lobbies?.games?.["team"]?.[0];
-    const special = this.lobbies?.games?.["special"]?.[0];
+    const lobbies = this.lobbies;
+    const isSingle = lobbies?.mode === "single";
+    const singleLobby = lobbies?.mode === "single" ? lobbies.lobby : undefined;
+    const ffa =
+      lobbies?.mode === "multi" ? lobbies.games?.["ffa"]?.[0] : undefined;
+    const teams =
+      lobbies?.mode === "multi" ? lobbies.games?.["team"]?.[0] : undefined;
+    const special =
+      lobbies?.mode === "multi" ? lobbies.games?.["special"]?.[0] : undefined;
 
     return html`
       <div class="flex flex-col gap-4 w-full px-4 sm:px-0 mx-auto pb-4 sm:pb-0">
@@ -148,47 +157,74 @@ export class GameModeSelector extends LitElement {
         </div>
         <!-- Game cards grid -->
         <div
-          class="grid grid-cols-1 sm:grid-cols-[2fr_1fr] gap-4 sm:h-[min(24rem,40vh)]"
+          class="grid grid-cols-1 gap-4 sm:h-[min(24rem,40vh)] ${isSingle
+            ? ""
+            : "sm:grid-cols-[2fr_1fr]"}"
         >
-          <!-- Left col: main card (desktop only) -->
-          ${special
-            ? html`<div class="hidden sm:block">
-                ${this.renderSpecialLobbyCard(special)}
-              </div>`
-            : ffa
-              ? html`<div class="hidden sm:block">
-                  ${this.renderLobbyCard(ffa, this.getLobbyTitle(ffa))}
-                </div>`
-              : nothing}
+          ${isSingle && singleLobby
+            ? html`
+                <!-- Single lobby mode: one full-width card -->
+                <div class="hidden sm:block">
+                  ${singleLobby.publicGameType === "special"
+                    ? this.renderSpecialLobbyCard(singleLobby)
+                    : this.renderLobbyCard(
+                        singleLobby,
+                        this.getLobbyTitle(singleLobby),
+                      )}
+                </div>
+                <div class="sm:hidden">
+                  ${singleLobby.publicGameType === "special"
+                    ? this.renderSpecialLobbyCard(singleLobby)
+                    : this.renderLobbyCard(
+                        singleLobby,
+                        this.getLobbyTitle(singleLobby),
+                      )}
+                </div>
+              `
+            : html`
+                <!-- Left col: main card (desktop only) -->
+                ${special
+                  ? html`<div class="hidden sm:block">
+                      ${this.renderSpecialLobbyCard(special)}
+                    </div>`
+                  : ffa
+                    ? html`<div class="hidden sm:block">
+                        ${this.renderLobbyCard(ffa, this.getLobbyTitle(ffa))}
+                      </div>`
+                    : nothing}
 
-          <!-- Right col: FFA + teams (desktop only) -->
-          <div class="hidden sm:flex sm:flex-col sm:gap-4">
-            ${special && ffa
-              ? html`<div class="flex-1 min-h-0">
-                  ${this.renderLobbyCard(ffa, this.getLobbyTitle(ffa))}
-                </div>`
-              : nothing}
-            ${teams
-              ? html`<div class="flex-1 min-h-0">
-                  ${this.renderLobbyCard(teams, this.getLobbyTitle(teams))}
-                </div>`
-              : nothing}
-          </div>
+                <!-- Right col: FFA + teams (desktop only) -->
+                <div class="hidden sm:flex sm:flex-col sm:gap-4">
+                  ${special && ffa
+                    ? html`<div class="flex-1 min-h-0">
+                        ${this.renderLobbyCard(ffa, this.getLobbyTitle(ffa))}
+                      </div>`
+                    : nothing}
+                  ${teams
+                    ? html`<div class="flex-1 min-h-0">
+                        ${this.renderLobbyCard(
+                          teams,
+                          this.getLobbyTitle(teams),
+                        )}
+                      </div>`
+                    : nothing}
+                </div>
 
-          <!-- Mobile: special, ffa, teams inline -->
-          <div class="sm:hidden">
-            ${special ? this.renderSpecialLobbyCard(special) : nothing}
-          </div>
-          <div class="sm:hidden">
-            ${ffa
-              ? this.renderLobbyCard(ffa, this.getLobbyTitle(ffa))
-              : nothing}
-          </div>
-          <div class="sm:hidden">
-            ${teams
-              ? this.renderLobbyCard(teams, this.getLobbyTitle(teams))
-              : nothing}
-          </div>
+                <!-- Mobile: special, ffa, teams inline -->
+                <div class="sm:hidden">
+                  ${special ? this.renderSpecialLobbyCard(special) : nothing}
+                </div>
+                <div class="sm:hidden">
+                  ${ffa
+                    ? this.renderLobbyCard(ffa, this.getLobbyTitle(ffa))
+                    : nothing}
+                </div>
+                <div class="sm:hidden">
+                  ${teams
+                    ? this.renderLobbyCard(teams, this.getLobbyTitle(teams))
+                    : nothing}
+                </div>
+              `}
         </div>
 
         <!-- Solo: full width, desktop only -->

src/core/Schemas.ts

@@ -164,11 +164,23 @@ export const PublicGameInfoSchema = z.object({
   publicGameType: PublicGameTypeSchema,
 });
 
-export const PublicGamesSchema = z.object({
+const SingleLobbyGamesSchema = z.object({
+  mode: z.literal("single"),
+  serverTime: z.number(),
+  lobby: PublicGameInfoSchema,
+});
+
+const MultiLobbyGamesSchema = z.object({
+  mode: z.literal("multi"),
   serverTime: z.number(),
   games: z.record(PublicGameTypeSchema, z.array(PublicGameInfoSchema)),
 });
 
+export const PublicGamesSchema = z.discriminatedUnion("mode", [
+  SingleLobbyGamesSchema,
+  MultiLobbyGamesSchema,
+]);
+
 export class LobbyInfoEvent implements GameEvent {
   constructor(
     public lobby: GameInfo,

src/server/IPCBridgeSchema.ts

@@ -23,6 +23,7 @@ export type MasterMessage = z.infer<typeof MasterMessageSchema>;
 const WorkerLobbyListSchema = z.object({
   type: z.literal("lobbyList"),
   lobbies: z.array(PublicGameInfoSchema),
+  clientCount: z.number(),
 });
 
 const WorkerReadySchema = z.object({

src/server/MasterLobbyService.ts

@@ -19,12 +19,17 @@ export interface MasterLobbyServiceOptions {
   log: typeof logger;
 }
 
+const CCU_SINGLE_LOBBY_THRESHOLD = 1500;
+const SINGLE_LOBBY_ROTATION: PublicGameType[] = ["special", "team", "ffa"];
+
 export class MasterLobbyService {
   private readonly workers = new Map<number, Worker>();
   // Worker id => the lobbies it owns.
   private readonly workerLobbies = new Map<number, PublicGameInfo[]>();
+  private readonly workerClientCounts = new Map<number, number>();
   private readonly readyWorkers = new Set<number>();
   private started = false;
+  private singleLobbyRotationIndex = 0;
 
   constructor(
     private config: ServerConfig,
@@ -49,6 +54,7 @@ export class MasterLobbyService {
           break;
         case "lobbyList":
           this.workerLobbies.set(workerId, msg.lobbies);
+          this.workerClientCounts.set(workerId, msg.clientCount);
           break;
       }
     });
@@ -109,13 +115,27 @@ export class MasterLobbyService {
     return result;
   }
 
+  private getTotalCCU(): number {
+    let total = 0;
+    for (const count of this.workerClientCounts.values()) {
+      total += count;
+    }
+    return total;
+  }
+
   private broadcastLobbies() {
+    const singleLobbyMode = this.getTotalCCU() < CCU_SINGLE_LOBBY_THRESHOLD;
+    const publicGames = singleLobbyMode
+      ? this.buildSingleLobbyBroadcast()
+      : {
+          mode: "multi" as const,
+          serverTime: Date.now(),
+          games: this.getAllLobbies(),
+        };
+
     const msg = {
       type: "lobbiesBroadcast",
-      publicGames: {
-        serverTime: Date.now(),
-        games: this.getAllLobbies(),
-      },
+      publicGames,
     } satisfies MasterLobbiesBroadcast;
     for (const worker of this.workers.values()) {
       worker.send(msg, (e) => {
@@ -126,7 +146,63 @@ export class MasterLobbyService {
     }
   }
 
+  private buildSingleLobbyBroadcast() {
+    const allLobbies = this.getAllLobbies();
+    const type = SINGLE_LOBBY_ROTATION[this.singleLobbyRotationIndex];
+    const lobby = allLobbies[type][0];
+    // If the active rotation type has no lobby yet, fall back to any available lobby.
+    const activeLobby =
+      lobby ?? SINGLE_LOBBY_ROTATION.map((t) => allLobbies[t][0]).find(Boolean);
+    return {
+      mode: "single" as const,
+      serverTime: Date.now(),
+      lobby: activeLobby,
+    };
+  }
+
   private async maybeScheduleLobby() {
+    const singleLobbyMode = this.getTotalCCU() < CCU_SINGLE_LOBBY_THRESHOLD;
+
+    if (singleLobbyMode) {
+      await this.maybeScheduleSingleLobby();
+    } else {
+      await this.maybeScheduleAllLobbies();
+    }
+  }
+
+  private async maybeScheduleSingleLobby() {
+    const allLobbies = this.getAllLobbies();
+    const type = SINGLE_LOBBY_ROTATION[this.singleLobbyRotationIndex];
+    const lobbies = allLobbies[type];
+
+    // Advance rotation when the current lobby has started.
+    if (lobbies[0]?.startsAt !== undefined) {
+      this.singleLobbyRotationIndex =
+        (this.singleLobbyRotationIndex + 1) % SINGLE_LOBBY_ROTATION.length;
+    }
+
+    // Clean up any stale lobbies from the other two types (don't schedule more of them).
+    // We only need to manage the active type.
+    if (lobbies.length >= 2) return;
+
+    const nextLobby = lobbies[0];
+    if (nextLobby && nextLobby.startsAt === undefined) {
+      this.sendMessageToWorker({
+        type: "updateLobby",
+        gameID: nextLobby.gameID,
+        startsAt: Date.now() + this.config.gameCreationRate(),
+      });
+    }
+
+    this.sendMessageToWorker({
+      type: "createGame",
+      gameID: generateID(),
+      gameConfig: await this.playlist.gameConfig(type),
+      publicGameType: type,
+    } satisfies MasterCreateGame);
+  }
+
+  private async maybeScheduleAllLobbies() {
     const lobbiesByType = this.getAllLobbies();
 
     for (const type of Object.keys(lobbiesByType) as PublicGameType[]) {

src/server/WorkerLobbyService.ts

@@ -88,7 +88,11 @@ export class WorkerLobbyService {
           publicGameType: gi.publicGameType!,
         } satisfies PublicGameInfo;
       });
-    process.send?.({ type: "lobbyList", lobbies } satisfies WorkerLobbyList);
+    process.send?.({
+      type: "lobbyList",
+      lobbies,
+      clientCount: this.gm.activeClients(),
+    } satisfies WorkerLobbyList);
   }
 
   private setupUpgradeHandler() {