new secrets in left 4 dead 1!!!!

me and my friend were playing left 4 dead we were at the gas station. and we were playing on expert and we were being chased by a tank. so we ran into the safe room of course the ai's died and at first we were gonna try to hide on the couch but then i decided to go over to the weapons so i got on top of the water dispenser. and i kept walking forward to see how far i could get and then i fell in this hole behind these boxes and my friend jumped on top of me. he said ha im on top of you. and then the tank came in and started hitting him and when he finally fell in the hole the tank finally died and i was unharmed :p it was hilarious. the other secret spot was in the generator room. ya know those 2 blue things by the fuse box. well if you jump on one of knobs on it then you can jump on top of the i guess i'll call it a steam heater? then if you look at the door there's this little ledge that you can jump on. note: you can't alert the horde from there. and beware of smokers. happy killings:)