Fun game and really well done :)

I like that you got different enemies (only had one in my game :P ) and I definitely feel lost jumping around your level. Would be nice to have a map, but maybe I just didn't find it? or its not in the demo? Also, haven't found the boss or air dash yet (did find the extra health tank though!), but I'm sure they're nice :P

The camera is a little wonky sometimes, the character sometimes end ups at the bottom or side of the screen instead of close to the centre. Also the character sliding to a stop made stopping on platforms challenging at first, but I got used to it.

Also, I liked the art and the opening "boss" encounter that forces you underground was exciting. Looking forward to playing more :)

More fellow metroidvania devs!
Ok so first and foremost...well done! This was super impressive for a month of work.  I was already impressed..and then I found the boss, very nice touch. You also got saving in there! I just needed a feeeew more days to get that implemented into mine, alas. 

I'm assuming, based on the "demo version - subject to change" that you guys are wanting to develop this into a full release? If that's the case, I hope you won't mind if I offer some constructive feedback based on my playthrough. 

On my second playthrough, I accidentally found the end of the demo without ever encountering an enemy, though it happened fast and I can't remember how I pulled it off, but just something to watch out for. 

The camera likes to jitter a bit, especially when the player walks up certain slopes. There were also some sections , when the player jumps, where the camera might follow the player vertically more than it should, made me feel disoriented while I was jumping (again, only sometimes.)

There almost feels like there's  a slight input lag with the shooting. Barely, but enough so that sometimes when I missed an enemy it didn't always feel like it was my fault. 

Lastly, I would use a much louder sound effect when the projectiles hit the enemies. You've got some great particle effects, and a nice juicy loud sound effect would make the projectiles feel nice and give them a nice feeling of impact. Currently, especially with the volume turned down I couldn't always tell if I hit an enemy or not. 

I loved the hand-drawn art style of everything. The particle effects were great. The levels were interconnected, and I found it very easy to memorize my way around after a few loops (also a positive.) I like the dash quite a lot, very unique take with the effect! For a demo the difficulty is well balanced as well. Overall, very impressive work, I hope to see this on Steam someday!