The last 5 seconds show potential. What you're going to want to do is get new sheets of paper and trace the background onto its own sheet. Then trace the drawings of Sonic you currently have onto their own separate papers. After you've done that you're going to find the halfway point between each drawing of Sonic you have and draw Sonic there. When you've done that do it again and you'll have a fairly smooth animation.
Truth.
Edit: Internet connection's pretty slow at the moment, but what I saw of that vid looks gorgeous. Love the gigantic head sculpture and it seems like there's a lot of depth- that island is so far in the background.
Anyone else read this terribly wrong at first? No? Mmmkay, bedtime.
And to make this post somewhat relevant. I like the more traditional top to that checkpoint.
For the first problem, could you not just have the tree or whatever go semi-transparent when you're behind it so that you could still see? And just have like.. another tile that is roughly the shape of the bottom of said tree that is used for collisions?
Of course whichever is easier is probably the way to go
It's the program I use to back all my work/music/videos to an external drive. There's also 25GB of storage on Skydrive if you don't have an external- all you need is a Windows Live ID. You said everything's go so well that you should watch your back and a lot of people fall victim to data loss, so this is one way to do that.