Over-the-top Shmup/STG with mouse control for movement. Has a lot of similarities to Akashicverse by the same developer. The game defaults to mouse control but there is an option for gamepad. There's a shop system to unlock moves and increase stats.
I think the crazy speed potential of mouse control fits well with the kind of bosses and stage design in Endless Shirafu games. They tend to have fast paced and unique attacks which require memorization to deal with. Mouse control doesn't make those aspects redundant and potentially gives the player a higher 'power level' so it's interesting to test the concept here.
∀stralbringer can be really challenging if you try playing with base equipment and avoiding the shop. The skill ceiling with just the base tools seems really high. Mouse movement control has crazy potential & grazing/bullet absorb mechanics with this have some interesting synergy (seems similar to the Psyvariar mobile game).
If you want it to get easier you can power up over progress and gain access to additional Methods/Skills. The strange thing is you barely need to scratch the surface of the mechanics to clear the Early Access / non-DLC content. This personally made most of the mechanics seem underbaked because they just don't matter. The game felt 'cleaner' with access to only initial tools but once you expand to the full set of abilities this explodes out of hand and becomes kind of messy.

If you want endgame content or English language support wait for the game to exit Early Access. The base game is similar to if Akashicverse was missing 1-2 of the final stages. Pricing seems reasonable regardless.

note: the trial and current Early Access version appear to require you to set the Windows Region setting 'Language for non-Unicode programs' to Japanese to run properly. Otherwise it will crash at launch.