diff -r 1ea6554d703e -r e21cfda0edde src/proto2/Application.cc
--- a/src/proto2/Application.cc	Mon Nov 10 21:58:38 2008 +0000
+++ b/src/proto2/Application.cc	Tue Nov 18 22:58:50 2008 +0000
@@ -78,9 +78,9 @@
                 }
             }
             
-            // check for valid combinations of arugments
-            if (!(arg_server xor !arg_connect.empty()))
-                throw ArgumentError("must supply *exactly* one of --server/--client");
+            // check for invalid combinations of arugments
+            if (arg_server and !arg_connect.empty())
+                throw ArgumentError("cannot be both server and client");
         }
 
     public:
@@ -102,15 +102,16 @@
                 if (arg_graphics)
                     engine.setupGraphics();
 
-                // setup either network server or client
+                // setup either network server, client or singleplayer
                 if (arg_server) {
                     engine.setupNetworkServer(arg_port);
 
                 } else if (!arg_connect.empty()) {
                     engine.setupNetworkClient(arg_connect, arg_port);
                 
-                } else
-                    assert(false);
+                } else {
+                    engine.setupSinglePlayer();
+                }
 
                 // run the main loop
                 engine.run();