In order to be able to experience the full potential of the game, it is very important that you are connected to a stable network and that your device's signal is at full strength.
Full WiFi bars or mobile data coverage in themselves are not a full guarantee for solid connections as local networks can occasionally slow down and get overburdened. This applies especially if you are playing in a mobile environment (car, train, etc.) or on underground public transport.
We strongly recommend playing on a stable wireless connection with a good internet service provider, or at least on a solid 3G or 4G connection with a reliable service provider, as with any other kind of online service.