fixed 

That's it, but it looks like you've accidentally replaced it with pure white, and also above the shrooms.

No: just that the 1 px wide dark line should go, and maybe have a few small blades of grass shoot up.

I'm abit confused, did you mean something like this?

I agree with Manupix, I think it would be a good idea to better incorperate the horizon line into the ground.

I think that game will speak of mushrooms

Kill that horizon line and this is perfect =)