Thank you a lot :D parallax was already implemented in the game, but that reference is going to be helpful :D

Don't fret!  (Unless you're rocking out that is). I suppose the color of the lighter side of your mountains could contrast a little better with the shadow on the front set of clouds.  I'm bad with color unless I start fresh so I'm sorry I can't help more with that problem.  The other thing I thought about is how your background will move as the screen scrolls.  Some games just scroll the background along with the sprites, but that can be kind of 'blah'.  To spice it up I'd think about incorporating some Motion Parallax.  You can add a nice effect by moving parts of the background meant to be far away a little slower than parts that are intended to be closer.  You can find animation tutorials, videos, and art examples all over.  Study them and use the effect how it best suits you.  This is one of my favorites here in the gallery, but you can find lots of others by using the search feature.  I hope that helps too. 

thanks you too :)

In game the tank is not supossed to turn, but can spawn from both sides, so i'll take that into account

Any other weakness on this piece? i really don't want to mess up with this project, i need to know 

Welcome to PJ!  This looks great.  Aside from the things eishiya mentioned, there aren't really any big concerns I can see.  The biggest one that I can think of, especially for a game, is the consistency in lighting.  Palettes, form, and color aside, if a stage has specific lighting, you need to always have that applied to your game sprites.  The tank for example (which is really well put together btw) is matching the lighting of the background just right.  But if the tank turns to go the other way there lighting will be wrong.  For sprites that will turn you could keep the lighting a little more generic, but in my opinion the more you put in the more you'll get out of it.  So it might behoove you to create a secondary Sprite set for when they turn.  Twice the work maybe, but it'll look twice as thought out.  

You probably already knew that, but I wanted to make sure because I know that those little details can make or break a project.  Keep up the nice work! 

Omg, that was fast :O

I'm glad you liked the tank (no, like... i'm actually REALLY happy for that )

Somewhat I sensed the art style difference between components where kind of "unaccurate"... but something like "scale consistency" would never have gone throught my mind, that's some advanced knowledge you are giving me and i'm very thankful for that :D

Btw, your pixel-art is fantastic O.o
 

The quickest way to earn those points is to comment and rate xP it can take a few days for a piece to be approved, but comments and ratings are instantaneous, and they do more to introduce you to the community :]

The tank and mountains look great, but the ground and grass don't look like they're part of the same world/game. They're stylised in a different way, with cartoonier colours and less sense of depth.

The grass in the background is huge! Makes the tank and character look mouse-sized. If that sense of small scale is intentional, then I think the mountains in the background should be made larger as well, so that they don't fit in the frame, to give the scene a more consistent sense of scale.