darkSpyro

I think the environments and main character are all looking pretty nice! The lighting especially makes it look pretty dang cool

The boss designs need some work IMO. The top one looks fine enough, but there are too many spikes on the head and chin. Lessen that maybe. Also the other ones look fairly generic IMO and don't feel like bosses. I'd suggest working on those a little bit more.

Pretty good lighting, creative boss design (at least the first one), and interesting artstyle. You have something quite unique on your hands. Can you give some information about how the gameplay works? No problem if it's a bit too early for that.

The in-game graphics look nice and the use of colour is pretty cool but the main menu is absolutely awful and you should look at good game covers or hire an artist. Maybe re-work the main character too.

UI and boss design definately needs work. While the overall art style is pretty, the designs are pretty forgettable with spike overuse and generic shapes, and the menu just looks put together with little thought(more emphasis on the boss or the character? Background?).

There's no harm if there are no artists in your team, but if you can't call a friend of a friend to help, do check out some references on simple character design which are everywhere on the internet. Make your enemy/boss immediately indentifiable. Shapes shapes, the shilhouette changes everything, etc. Think like Eggman's creations - do you remember the mishmash of balls in the Sonic Advance series or the Egg Viper, Egg Dragon, heck, even Egg Wyvern?

multiple things, let's start with the name:

poly's adventure? really? sounds like a bad flash game. consider changing the title to something different, maybe polycolypse or soemthing i dunno

the main character, polygonishness aside, is very bland. consider making him like an animal or something

the bosses are way to overdesigned, and it's not liek you're working with phenomenal graphics so thats not a good thing. think of a concept and stick with it

the hud looks really bland too

I get that you're going for a low polygon, simpler style, but it looks very unrefined and sharp. The one boss looks odd with so many thin, jagged points. The main character looks closer to a test dummy at this stage and could use a little more personality and flair. Having more than 2 colors on him would be good and only 2 dots for eyes as the entire face isn't exactly helpful.

I personally think you're doing a good job.

Considering these aren't finalised yet, they have good designs.