Most games tend to be resource-hungry and may crash without enough memory or CPU time. 
 
If you are not able to launch the game and get to the level select screen, or are able to play and are experiencing  crashes or freezes in-game, start by making sure you have 100 MB of extra free space for caching purpose.  Apps needs some space to write and store temporary files. If your device's storage space is full, offload some of your data or delete some old unused apps to free up space.  It's always a good idea to power-cycle the device from time to time to clear memory.
 
Connection quality:
Another factor that may affect game stability would be a poor online connection. We recommend a strong WiFi connection (as opposed to 3G/4G). Even if you have good signal strength showing for your WiFi connection, your bandwidth may be limited if the network is congested (For example, if there are many other users sharing the network and/or others are doing bandwidth-intensive activities such as streaming video.)