diff --git a/src/server.ts b/src/server.ts
index bb51278..60ded16 100644
--- a/src/server.ts
+++ b/src/server.ts
@@ -70,9 +70,75 @@ if (isMain) {
             ws.send(JSON.stringify({ type: "player_list", players: list }));
             break;
 
-          case "join_room":
-            // TODO: implement room creation / joining logic
+          case "create_room": {
+            // Player creates a room and becomes host
+            if (player.roomId) {
+              ws.send(
+                JSON.stringify({ type: "error", message: "already_in_room" }),
+              );
+              break;
+            }
+            const roomId = createRoomId();
+            const room: Room = { id: roomId, players: [playerId] };
+            rooms.set(roomId, room);
+            player.roomId = roomId;
+            ws.send(JSON.stringify({ type: "room_created", roomId, playerId }));
             break;
+          }
+
+          case "join_room": {
+            // Player joins another player's room
+            const targetId = msg.targetId as string | undefined;
+            if (!targetId || !players.has(targetId)) {
+              ws.send(
+                JSON.stringify({ type: "error", message: "invalid_target" }),
+              );
+              break;
+            }
+            if (player.roomId) {
+              ws.send(
+                JSON.stringify({ type: "error", message: "already_in_room" }),
+              );
+              break;
+            }
+            const target = players.get(targetId)!;
+            if (!target.roomId || !rooms.has(target.roomId)) {
+              ws.send(
+                JSON.stringify({
+                  type: "error",
+                  message: "target_not_in_room",
+                }),
+              );
+              break;
+            }
+            const room = rooms.get(target.roomId)!;
+            if (room.players.length >= 2) {
+              ws.send(JSON.stringify({ type: "error", message: "room_full" }));
+              break;
+            }
+            // Add player to room
+            room.players.push(playerId);
+            player.roomId = target.roomId;
+
+            // Notify both players
+            ws.send(
+              JSON.stringify({
+                type: "room_joined",
+                roomId: target.roomId,
+                peerId: targetId,
+                peerNickname: target.nickname,
+              }),
+            );
+            target.ws.send(
+              JSON.stringify({
+                type: "peer_joined",
+                roomId: target.roomId,
+                peerId: playerId,
+                peerNickname: player.nickname,
+              }),
+            );
+            break;
+          }
 
           default:
             ws.send(JSON.stringify({ type: "error", message: "unknown_type" }));
@@ -83,8 +149,31 @@ if (isMain) {
     });
 
     ws.on("close", () => {
+      // Clean up room if player was in one
+      if (player.roomId) {
+        const room = rooms.get(player.roomId);
+        if (room) {
+          room.players = room.players.filter((p) => p !== playerId);
+          // Notify remaining players
+          for (const pId of room.players) {
+            const p = players.get(pId);
+            if (p) {
+              p.ws.send(
+                JSON.stringify({
+                  type: "peer_left",
+                  roomId: player.roomId,
+                  peerId: playerId,
+                }),
+              );
+            }
+          }
+          // Delete empty rooms
+          if (room.players.length === 0) {
+            rooms.delete(player.roomId);
+          }
+        }
+      }
       players.delete(playerId);
-      // TODO: clean up rooms if player was in one
     });
 
     ws.send(JSON.stringify({ type: "welcome", id: playerId }));