It's a nice concept and all but there's a couple things wrong here:
- Your deltas need a LOT of fixing. Try making your sky deltas (1,1) then gradually increasing as you go down the list in the .def (of course certain deltas will remain the same though) after doing so your bounds will need a mega fix.
- The Lens flare is nice, but it could use a flash animation. Its deltas are messed up as well.
Also, I know this is from a source, but the edges of the building/foreground are poorly cut. The edges have white pixels all over, check some alias tutorials man.
The shadows look really bad, you shouldn't scale them that way. Those need a fix.
Also, you leave a lot of large sprites in the .sff, this can cause lag. Try cutting your images up more. It'll avoid color loss (if any) and be less laggy.
Also, you left debug on, that can also cause lag.
A nice concept all in all, but much work is needed. I hope to see an update.