1 exit down, 4 to go
I am referring to these
Marble
(http://www.mobygames.com/images/shots/l/178556-lemmings-psp-screenshot-bridge-builders-saving-fellow-lemmings.jpg)
Pillar
(http://media.moddb.com/images/mods/1/18/17499/frmbuf002.png)
Fire
(http://www.mobygames.com/images/shots/l/178555-lemmings-psp-screenshot-blocker-bomber.jpg)
Crystal
(http://1.bp.blogspot.com/_H0J0JGu7zbw/SlRRNQqhdRI/AAAAAAAACF4/4COMkYxhBis/s400/lemmings.jpg)