Along with Sky Force: Reloaded, one of the best euroshmups out there, period. Very meditative, with high replayability value, both on PC and mobile.

Old style game with its charm. Worth the 9,99 EUR I spent on it.

It's a decent shoot'em up similar to classic games, definitely NOT a bullet hell though.
It's more of an incremental one as well, you gain stars for upgrades and you can replay old stages for which you also unlock higher difficulties. Your first and foremost challenge will be memorising the stages though as that is crucial to fulfilling your objectives. Going back and forth between previous stages could still be too repetitive for some, but I would say there is enough variation you can get with the various ships and other improvements.

At the end of the day I can't recommend it though, unless you can live with not getting all achievements or have a really high threshold for frustration. If you really want to play, play the first one or for this game I'd rather recommend the mobile version. I was already NOT looking forward to the latter stages because they are just ridiculously hard. Though I get that this might be an improvement that players may have criticised on the regular Sky Force, I don't see that as a plus. Maybe I'm wrong but I don't recall some of the issues I was having with this version from the android one. The one that led to me quitting the game right now and leaving this review being that in one of the latter stages enemies with screen stretching lasers show up quicker and already shoot even when not on the screen with hardly a chance to react. Yes, the game lives off of you memorising everything but some of it is just too ridiculous.