I was wondering the same, its a shame!

I saw the dev had made a few posts in Chinese and one in English back in mid-January but nothing since. So it seems likely development has paused or stopped. Bummer, I only "discovered" this game today, and it seemed so promising.

Here's dev's posts:
https://gtm.steamproxy.vip/profiles/76561199389663275/posthistory/

Although I continue irrationally to buy Early Access games, the one thing devs are never transparent about early on is whether they "need" a lot of EA sales to fund continued development of the game. Since they aren't required to be transparent about that when they launch a game in EA, it's always a crap shoot if development will continue or just be one update or so and a cloud of abandoned dust because the EA sales fell short of expectations and didn't bring in sufficient funds to continue development. :P

PLease Update the Game. You cant play the Mission Feint even on Easy, since you rely on Weapon Upgrades like Mutlishot, Armor Penetration etc. You cant even select.
I have Unlokced all of them for my Cannon, but still doesnt Work!

The Mission Feint is extremely hard but possible to beat on easy mode!!!!! On normal mode its impossible to beat!!!!!! The lack of supply drops the lack of Main cannon upgrades functioning and the disparity of upgrade drops which often times give u the most useless choices

Looks like DOA huh? Last time I buy into early access lol