If you look in any of the previous demos for the game, you'll notice that the Background is always scrolling at the same speed, no matter how fast you are moving. This is no longer the case, as now the background speed is consistant with the foreground speed. I think it looks quite a bit nicer.
One thing I really miss from my days working with Allegro is the ability to have the program wait for the vertical retrace. My biggest problem graphically with Blocky Man is the constant tearing due to scrolling. I remember an Allegro side scroller I once worked on, where the scrolling was absolutly crisp because I could wait for V-Sync to redraw the screen. Sadly, I don't believe SDL provides this capibility, which is a shame.
Anyways, I can finally get back to working on the level. I need to start working on those missile turrents. I've actually had the graphics for the missile done for quite some time, but haven't gotten around to programming it.
That seems like a major limitation to me if that's the case. Have you thought about jumping into using Direct3D directly for your next project? Once you've got a decent 2D sprite library up and running, it's really quite easy to use.