The gamecard includes a link to https://www.gog.com/game/sunblaze_demo but that page no longer exists.

Will the Linux version be available on GOG as well?

What's with her mouth in the screenshots? Graphics error?

What mouth?

There is no mouth. If you watch the vid it looks like she has none.

She does have to scream, though.

Prequel?

Looks like Roll decided to move away from his brother's shadow and got her own game.

Can't you see it? Her mouth appears to be black. See attachment, above is original and below I made it red. I see the same black mouth in the video, it's really weird.

You see, she's a superhero in training. One of those superpowers is randomly growing a red beard.

It's just the outline around her head. I know it's a big-head cartoon style, but generally speaking, mouths are not placed under one's chin while extending the entire width of one's head, nor would she presumably have her mouth hanging open at all times.

I love that idea!

As eric5h5 said (and I'm also pretty sure) that black line is the outline.
The lower part was removed in the pixel art version of the characters to allow more expressive upper part of the head, like the eyes.

Also other NPCs don't have a mouth, see attached screenshot.
BUT we can clearly see an inconsistency here with the outline!

I second this.

The game looks fun and I'd certainly buy if the Linux version is made available.

Yeah, it is an inconsistency.

But that's this game's art style for you...