Why I get a weird line on the screen.

That's a strange one. I've seen this happen with tiled backgrounds, that have a pixel of padding on the top/bottom. But, never across everything in the layout like this.

There is no invisible sprites or anything running across the entire area, that might be causing it?

EDIT: Now that I'm looking it over a second time. It looks like something about the top of your grass image. The background on that Sprite is completely transparent right? No padding, or pixel width line right at the top in the Animations Editor? Could try just cutting it shorter, so there is less space above the actual grass tips. To me it looks like something about that Sprite Object.

Good catch lennaert. That's gotta be it. I didn't look over at the Project/Object Tree. I'm still waking up over here XD

Turn that object Non Visible in the left side, and it'll not show. EDIT: Or just push it to the bottom of the Z Order if you want it visible but hidden in the background for any reason.