I see all these negative reviews complaining about lack of support and replay value, but I just want to say that despite its problems, this game is really fun for the 2$ I paid for it on sale.
The gameplay gets pretty intense, especially late in a round when tons of enemies are spawning, and it's an enjoyable challenge figuring out how to best kite and kill enemies and when to use bombs and such.
When you buy this game, be aware what you are paying for. Arcadia is a casual shooter (As clearly mentioned) that is not meant to entertain you for long periods of time like other games. This game is fun to play on and off when you don't have time for other deeper games, and it fulfills that goal excellently. Don't buy this game if you are looking for a hardcore game to sink many hours into to beat or to become the best at it.
Whether this game is being actively updated or not isn't really relevant. The game mechanics are solid and very entertaining in a casual situation, and I'm happy having given a one time payment of 2$ and receiving the end product I got.
One point that I want to given special mention to is the music in this game. Hearing the music in this game is like half the experience of playing this game. The dev of this game put together an awesome soundtrack for this game, which ends up making it extremely relaxing and enjoyable to play. The music in this game is techno and trance from Newgrnds (Steam censors the full site name for some reason), so if you like that kind of music you'll probably enjoy this game
As the description clearly states, "Arcadia is a fun, casual little shooter." And that's exactly what you get when you buy this game. Hardcore gaming experience for hundreds of hours of evolving gameplay, no. Fun 2d bullet-hell shooter with awesome music that's worth a few bucks, yes.