set lowest bound for zoomspeedup and tweak for ios

lib/routing/models/screen_edge.dart

@@ -46,8 +46,10 @@ Map<String, double> moveCameraWhenDraggingToScreenEdge({required ScreenEdge scre
   final double mapMoveSpeed;
   if (Platform.isAndroid) {
     mapMoveSpeed = 0.00015;
+  } else if (Platform.isIOS) {
+    mapMoveSpeed = 0.0017;
   } else {
-    mapMoveSpeed = 0.003;
+    throw Exception("Platform not supported");
   }
 
   final double moveCameraX;

lib/routing/views/map.dart

@@ -909,7 +909,11 @@ class RoutingMapViewState extends State<RoutingMapView> with TickerProviderState
     // The zoom is usually between 12 and 16, while 16 is more zoomed in.
     // We need to speed up the movement while zoomed out otherwise the movement is too slow.
     final zoom = cameraState.zoom;
-    final zoomSpeedup = 16 - zoom;
+    double zoomSpeedup = 16 - zoom;
+
+    // No negative zoom speedup otherwise the map would move in the opposite direction.
+    // And don't set to 0 otherwise the map would not move at all.
+    if (zoomSpeedup <= 0.5) zoomSpeedup = 0.5;
 
     await mapController?.easeTo(
       CameraOptions(