sadly its a mix of the device and app! the app is a really large file due to the amount of assets and the format/size of each of them,= so takes up a lot of ram meaning that it can only run on faster devices (which is what causes crashes when on some mobile devices!) D:
If you do manage to enter the game a way you can reduce it is by setting it to low quality and making sure you 'exit' the game when you close it as that's what will save your progress :)
I'm glad you like it and i hop changing the quality will help reduce lag :DD