This may be due to insufficient memory/capacity on your phone. Please close all running apps and then restart Brown Toys.
The forced close may also occur if the network (communication) environment is unstable. (When transporting, the communications may continuously move back and forth from Wi-Fi to 3G, 4G, and 5G.)
Please restart in a place with a smooth network (communication) environment. 

This may occur when running many apps at once or when the phone has not been restarted for a long time, as this may cause insufficient memory/capacity.
Please close other running apps or restart your phone.

Were you playing with a guest account?
Guest accounts cannot link data if you change your device. Please link to your LINE / Google / Apple account before changing devices.
If you log in with an account other than a guest account, you can save your data and play using the stored data even after changing devices.

Search for and install Brown Toys in the App Store.
If you log in with an account other than a guest account, you can save your data and play using the stored data even after changing devices.