Life got you down? The wife left you and your dog pooped on the carpet? Do you yearn for a simpler time, when you could just sit in a dark room, carefree, basking in the lovely glow of a CRT monitor, thwacking headcrabs with a low poly crowbar?
Boy do have the escapist solution for you! Check out this single player Half-Life mod: Half-Life: C.A.G.E.D.