I purchased Yars for PC through Steam yesterday, and would advise that you hold off on doing the same. The game is not as advertised.
There are two references to the game having an RPG-ish upgrade system in the description on Steam, and many other sites:
About The Game:
"Gain experience to upgrade and expand your armor and weapon capabilities"
"Upgrades and RPG elements - Gain experience while customizing your armor and weapon abilities."
I can assure you that _none_ of that is in the game. I played through the entire campaign which at times makes it seem as if upgrades are around the corner, but they never show up. And there's certainly no experience collecting happening at all.
This is a railshooter with 5 different enemies. Do not expect it to be a Panzer Dragoon for PC.
Additionally, Killspace Entertainment appears to have disappeared. Their twitter feed hasn't been updated since July, and their website, killspace.net, doesn't exist any more. So there's no one to complain to.
I've submitted a support request through Steam, but not expecting much. Just posting this as a warning.