I defeat boss (maybe lv6? 3way-ice ball boss) and I was defeated before message window appear. Then got "writing data fail" and keep loading forever...
Thank you :) Its pretty much designed to take some time to get used to, so the early losses are to be expected. Good luck on pushing through! Just to give you a bit of light at the end of the tunnel, the more experienced players I've talked to are generally able to maintain something like an 80% win rate with some pretty insane win streaks.
 "30s Hero"){kind=icon}
 "Idle Hero Tower Defense"){kind=icon}
 "Rogue Fable III"){kind=icon}
 "Crush Crush"){kind=icon}
Patch coming shortly!