Superworld was one of the earlier superhero RPGs, predating Marvel Super Heroes by a year. Like other Chaosium games (Call of Cthulhu, Runequest, etc), Superworld uses the Basic Roleplaying (BRP) universal rules set.
It is actually the 2nd edition, as Steve Perrin expanded Superworld from the booklet of the same name in the Worlds of Wonder box set (1982).
An interesting bit of history about Superworld is that George R.R. Martin (best known for Game of Thrones) developed his long-running Wild Cards anthology fiction series from his own Superworld campaign. Wild Cards chronicled the sudden appearance of an enhanced virus in an alternate 20th century. The virus killed most it touched, though a few became “Jokers” (with crippling mutations) and a very few individuals becoming Aces (Supers). George R.R. Martin edited, wrote a few of the short stories if I recall correctly, but most stories were penned by other science fiction / fantasy authors in a Shared World setting. (Like Thieves World!).
George went on to explain that he had been given a copy of Superworld as a birthday present and had spent the last year and a half running a Superworld campaign. As he has described in his own blog, this occupied all of his creative time – nothing that paid money was getting written. Now he was considering just what he could do with this experience in the way of a writing product that he could actually get paid for. We started negotiations for a campaign book. Frankly, I doubt Chaosium could have offered enough money to make it worth his while to do much work on such a book, but I was angling to get the rights to the campaign and do all the scut work myself. But then the axe fell.
Unable to create a new career for himself as a game supplement writer, George was forced back on his own resources to come up with a way to monetize his Superworld experience. Thus was Wild Cards born.The late Steve Perrin, A Brief History of SUPERWORLD
Superworld: The Superpowered Roleplaying Game [BOX SET]
1983 … Steve Perrin … Chaosium 2011-X
CONTENTS: Box contents sheet; Superheroes book; Superpowers book; Gamemasters book; Reference sheets; Player Character sheets; Gamemaster sheets; Character Silhouettes.
Box contents sheet
Early Chaosium box sets always had these contents sheets. They are invaluable for collectors now. Plus they had the Credits on the reverse side.
Superheroes book (32 pages)
For a Super world character creation example, see Dyson’s post: Tendriculous Rex.
Superpowers book (40 pages)
The art by Chris Marrinan and Markus Harrison is solid, with captions describing the pictures.
Gamemasters book (40 pages)
Reference sheets (8 pages)
Player Character sheets (8 total: 2 male & 2 female outlines)
Gamemaster sheets (Operatives sheet, Action Rank control sheet, Player control sheet)
This set had Chaosium catalog (Volume 2 Number 2 – Summer 1983), which is a great snapshot of the state of play at the company at that time.
I’ve seen a Superworld set with a 4-page errata sheet dated December 1984, which lists 1985 Chaosium products as Coming Soon.
Superworld was followed by two modules and a rules expansion (Bad Medicine for Dr. Drugs, A Companion to Superworld, Trouble for Havoc), but the line quickly petered out. That Havoc was already talking about its compatibility with Villains & Vigilantes and Champions RPGs was not a good omen for the future.