Pretty much the same as this one..
100 lines contest demo form Acknex resource site & it's a screen saver..

You just have to learn and be patient. Each engine has it's
ups and downs. The good thing about GS is that all
based around the C language and theres pretty much nothing
it can do. It's like any engine. Try to cram to much into
one or two loops and naturaly it's going to die..

There are tricks a programmer can do to overcome lag just
got to have the know how, but you proberly know all this.