Downloading game archives from unverified sources carries risks of malware or unwanted mining payloads.
If you already have this specific file and are trying to use it: Squad.51.vs.the.Flying.Saucers.part1.rar
The game features 2-player local co-op but does not support online multiplayer. Typical "Part 1" File Info Squad.51.vs.the.Flying.Saucers.part1.rar
Files from forum posts often require a password, which is usually listed in the original post where you found the link. Squad.51.vs.the.Flying.Saucers.part1.rar
