Really nice game, gotta be one of the most underrated ones on the market right now. Trading and train managing aspects are just right, not too simplistic or boring and not too complicated. Story is at least better than your average gacha game and doesn't feel like filler and afterthought like in some others. There is a lot of satisfying progression, both in terms of your roster and your train/trading/relationship with cities/challenges, etc. Art style and character designs are pleasant, soundtrack is also really good. Gacha seems pretty generous towards F2P, you will get decent amount of pulls by just playing the game and progressing in it.

Of course this game isn't perfect and the biggest downsides for me would be:

1. You have to log into your account every time when launching the game, it's a bit inconvenient even if signing with Google/Ujoy, so i hope they will add a remember your account feature eventually.
2. Most of dialogue doesn't have voiceovers, which is sad, because everything that had VAs was on good quality and added a lot to the immersion.
3. Almost every combat mission in this game requires you to spend energy, no matter if it's a mission for grinding upgrade resource, main story, side mission or timed event, all of them blue ball you by requiring "clarity". I guess you can't escape mobile gaming trends, and developers will roll with it if audience isn't strongly against it. To me it was really annoying, especially with main story missions, since i'm a bit addicted to this game lately, and wanted to complete all the content pretty much in one go, so it probably won't be that big of a deal for an average players, because you will get plenty of consumable that restore energy. 3.5. This one is also my personal complaint, because i'm not that much into mobile gaming, but i've already stumbled across this sidescrolling and card using type of combat in soooo many different gachas (FGO, Epic Seven, CounterSide, Reverse 1999, could be even more), so i think it wouldn't be a stretch to call it a little bit generic. But thankfully combat isn't one and only focus of this game, and even if it was, it's still more engaging and interesting than in most of the other similar ones. If you're not into that type of gameplay like me, you will just be able to auto skip all the unimportant encounters, while more challenging battles will require decent amount of strategic thinking and preparation, which keeps things interesting.

That being said, Resonance Solstice is surprisingly good and i dare to say it's one of the most hidden games right now. If you got bored of your main gacha and want to make a change, then i can't recommend it enough. I hope that it successfully finds its niche and thrives in it.