What's your device's resolution? If it's very small then I can understand it might be an issue, there's a minimum resolution after which it really causes problems. Battery drain is something I hadn't considered, it's a full PC game crammed onto mobile so I can understand it must have a lot more processing going on than a standard mobile game, I suppose there's not a lot I can do about that besides optimize.
Basically all the levels (including the one with the shrine) are tutorial levels, it's just that the first two levels are the only ones that admit to it. In any case, there's still a lot to be improved. I could leave certain mechanics (damage types, blocking) for later and I'd really like to make Voice talk less and have more infographics to show how turn order or the skills work.
In my head, all the music is likely slightly off. I have next to no experience, I'm surprised it's mostly okay and the home theme that got you but it is a bit more aggressive. There's still a few pieces you wouldn't have seen. I'll take a look at it sometime, though, people are going to hear it a lot.
... And the shrine is a bit janky because it involves talking to characters to progress the quest. I've had a couple of people not quite get it (especially because the fox technically IS an enemy).
Thanks for playing! Don't worry too much about what's after the Shrine unless you're looking for 'content'. After 0-3 there isn't anything new gameplay-wise.