This is a port to Common Lisp of a Flash tutorial on Parallax Scrolling that can be found on tutsplus.com.
To run this game place the files somewhere Quicklisp can find it, and execute the following in the REPL:
(ql:quickload :parallax-demo) (parallax-demo:start)
Decrease Speed :
Left arrow key.
Increase Speed :
Right arrow key.