diff --git a/public/static/js/game.js b/public/static/js/game.js
index 0bb29de..eba1b40 100644
--- a/public/static/js/game.js
+++ b/public/static/js/game.js
@@ -1,6 +1,6 @@
 'use strict';
 
-const GameType = Object.freeze({'SINGLE': 0, 'MULTI': 1, 'CHALLENGE': 2});
+const GameType = Object.freeze({ 'SINGLE': 0, 'MULTI': 1, 'CHALLENGE': 2 });
 
 (function () {
     var Game = {
@@ -215,8 +215,8 @@ const GameType = Object.freeze({'SINGLE': 0, 'MULTI': 1, 'CHALLENGE': 2});
             }
         },
 
-        getGameIdentifier: function() {
-            switch(Game.type) {
+        getGameIdentifier: function () {
+            switch (Game.type) {
                 case GameType.SINGLE:
                     return '/game/' + mapId;
                 case GameType.MULTI:
@@ -303,7 +303,7 @@ const GameType = Object.freeze({'SINGLE': 0, 'MULTI': 1, 'CHALLENGE': 2});
                     Game.showSummary();
                     document.getElementById('continueButton').style.display = 'none';
 
-                    
+
                 } else {
 
                     Game.panoId = this.response.place.panoId;
@@ -317,7 +317,7 @@ const GameType = Object.freeze({'SINGLE': 0, 'MULTI': 1, 'CHALLENGE': 2});
             });
         },
 
-        transitToResultMap: function() {
+        transitToResultMap: function () {
             // TODO: refactor - it is necessary for mobile
             if (window.getComputedStyle(document.getElementById('guess')).visibility === 'hidden') {
                 document.getElementById('showGuessButton').click();
@@ -353,7 +353,7 @@ const GameType = Object.freeze({'SINGLE': 0, 'MULTI': 1, 'CHALLENGE': 2});
         },
 
         loadHistory: function (history) {
-            if(!history)
+            if (!history)
                 return;
 
             Game.history = history;
@@ -385,9 +385,9 @@ const GameType = Object.freeze({'SINGLE': 0, 'MULTI': 1, 'CHALLENGE': 2});
                         Game.addGuessPositionToResultMap(round.result.guessPosition, null, true);
                     }
                     Game.scoreSum += round.result.score;
-                
 
-                    if(round.allResults !== undefined) {
+
+                    if (round.allResults !== undefined) {
                         for (var j = 0; j < round.allResults.length; ++j) {
                             var result = round.allResults[j];
                             if (result.guessPosition) {
@@ -514,7 +514,11 @@ const GameType = Object.freeze({'SINGLE': 0, 'MULTI': 1, 'CHALLENGE': 2});
                     break;
 
                 case 'game_not_found':
-                    MapGuesser.showModalWithContent('Error', 'The game room was not found by this ID. Please check the link.');
+                    MapGuesser.showModalWithContent('Error', 'The game was not found by this ID. Please check the link.');
+                    break;
+
+                case 'anonymous_user':
+                    MapGuesser.showModalWithContent('Error', 'You have to login to join a challenge!');
                     break;
 
                 default:
@@ -580,7 +584,7 @@ const GameType = Object.freeze({'SINGLE': 0, 'MULTI': 1, 'CHALLENGE': 2});
         },
 
         showResultMap: function (result, resultBounds) {
-            
+
             Game.transitToResultMap();
 
             Game.map.fitBounds(resultBounds);
@@ -637,48 +641,6 @@ const GameType = Object.freeze({'SINGLE': 0, 'MULTI': 1, 'CHALLENGE': 2});
                     Game.pov = this.response.place.pov;
                 }
 
-                // if(this.response.history) {
-
-                //     // game finished 
-                //     // delete everything but the last round
-                //     for (var i = 0; i < Game.rounds.length -1; ++i) {
-                //         var round = Game.rounds[i];
-        
-                //         if (round.realMarker) {
-                //             round.realMarker.setMap(null);
-                //         }
-                //         for (var j = 0; j < round.guessMarkers.length; ++j) {
-                //             var guessMarker = round.guessMarkers[j];
-                //             guessMarker.marker.setMap(null);
-                //             guessMarker.line.setMap(null);
-                //             if (guessMarker.info) {
-                //                 guessMarker.info.close();
-                //             }
-                //         }
-                //     }
-        
-                //     // Game.rounds = [];
-
-                //     for (var i = 0; i < this.response.history.length; ++i) {
-                //         var round = this.response.history[i];
-                //         Game.rounds[i] = { position: round.position, guessPosition: round.result.guessPosition, realMarker: null, guessMarkers: [] };
-                //         Game.addPositionToResultMap(true);
-                //         if (round.result.guessPosition) {
-                //             Game.addGuessPositionToResultMap(round.result.guessPosition, null, true);
-                //         }
-                //         Game.scoreSum += round.result.score;
-    
-                //         for (var j = 0; j < round.allResults.length; ++j) {
-                //             var result = round.allResults[j];
-                //             if (result.guessPosition) {
-                //                 Game.addGuessPositionToResultMap(result.guessPosition, result, true);
-                //             }
-                //         }
-                //     }
-
-                // }
-
-
             }, data);
         },
 
@@ -995,9 +957,9 @@ const GameType = Object.freeze({'SINGLE': 0, 'MULTI': 1, 'CHALLENGE': 2});
         document.getElementById("compass").style.transform = "translateY(-50%) rotate(" + heading + "deg)";
     });
 
-    if(roomId !== null) {
+    if (roomId !== null) {
         Game.type = GameType.MULTI;
-    } else if(challengeToken !== null) {
+    } else if (challengeToken !== null) {
         Game.type = GameType.CHALLENGE;
     }
 
diff --git a/src/Controller/GameController.php b/src/Controller/GameController.php
index 9585622..a4d0210 100644
--- a/src/Controller/GameController.php
+++ b/src/Controller/GameController.php
@@ -97,7 +97,7 @@ class GameController
     }
 
     public function getChallenge(): IContent
-    {
+    {   
         $challengeToken = $this->request->query('challengeToken');
 
         return new HtmlContent('game', ['challengeToken' => $challengeToken]);
@@ -239,8 +239,19 @@ class GameController
         $challengeToken_str = $this->request->query('challengeToken');
         $session = $this->request->session();
         $userId = $session->get('userId');
+
+        if (!isset($userId))
+        {
+            return new JsonContent(['error' => 'anonymous_user']);
+        }
+
         $challenge = $this->challengeRepository->getByTokenStr($challengeToken_str);
 
+        if (!isset($challenge))
+        {
+            return new JsonContent(['error' => 'game_not_found']);
+        }
+
         if(!$this->userInChallengeRepository->isUserParticipatingInChallenge($userId, $challenge)) {
             // new player is joining
             $userInChallenge = new UserInChallenge();