Help in making a system like Wolf Pack~ +REP (Need in GUI)

Level 9
Jul 11, 2009
Hello guys,
I need a system just like Wolf Pack.
Where mana(hunger points)drop every few seconds.
If your mana(hunger points)gets to zero,your hp will start dropping.
You can heal your hp by sleeping but if you have no mana
sleeping does not work at all.
And to mantain your hunger points,you need to feed on corpse(i think its made from cannibalize)
Cannibalize restores your mana(hunger points)

So what i need is that making mana drop every few seconds,then if mana gets to zero your hp will start dropping and sleep does not work.
But if you have mana and you sleep,your hp restores.
How to make Cannibalize that restores mp.

Just play the game in singerplayer to know what i'm talking about.

Link to wolfpack:

Thanks in advance