Ev Nova Heretic 1.0.10 .sit Files??? Im Trying To Download EV Nova For MAC OS, And The Stupid .sit Download Opens Up In Text Edit!!?

.sit files??? Im trying to download EV Nova for MAC OS, and the stupid .sit download opens up in text edit!!? - ev nova heretic 1.0.10

Included in the text processing and displays many gibberish ... Because I have an Intel Mac? OR am I use the new Leopard operating system? What the hell is going on here? Oh, and New EV is a game for Mac, so that its application should open or somthing, HELP