Sunjang Baduk is a variant of Go, which was common in Korea through the 16th century.
The first 16 moves are prescribed and Black makes the first free play, leading straight into a fierce middlegame. Perhaps this is why the character of Korean players is the way it is. The other main difference lies in the way of scoring. After all plays have been made, as many internal stones as possible are removed, leaving continuous boundaries. Then the totals of territory controlled are counted, with prisoners ignored. (source: the Hankuk Kiwon Guidebook)
BillSpight: Black's first "free" play is prescribed. He plays at the center of the board.
About scoring: The final borders cannot contain any stone in atari, but may contain cutting points. They need not be continuous. Points are not counted in seki.
About the merits (or not) of the scoring
John Fairbairn discusses Sunjang Baduk on MSO. Yours truly has analyzed a ko fight in a
PDF file there.
S_Cho: There are a few examples of Sunjang baduk (up to first 200 movements) online, originated from a go megazine published in 1934.
Sunjang baduk without Handicap : http://soonjang.netian.com/gibo/sinjung_1.htm
Sunjang baduk with Handicap (after black is set on Tengen, black moves first) : http://soonjang.netian.com/gibo/sinjung_2.htm
Sunjang baduk with Handicap (additional 4 black stones are set on the pre-determined positions, while another white one is set on Tengen) : http://soonjang.netian.com/gibo/sinjung_3.htm
About the merits (or not) of the scoring
Bill: People have long debated the merits of area scoring (ChineseScoring) vs. territory scoring (JapaneseScoring). (See TerritoryAndAreaScoring.) In my humble opinion, Korean scoring combines the advantages of both. Its only drawback is unfamiliarity.
EverCat: I wholeheartedly disagree - one of the joys of both Japanese and Chinese scoring is that the player who "controls" the majority of the board is (almost) always the winner "on the board" (ie before komi). I think that's beautifully logical, but it's not necessarily true here, is it?
Bill: Well, it's still about controlling, with more emphasis on surrounding. I don't see that it's any less logical.
Evercat: I think it's highly illogical. In essence, it says some stones on the board will be counted as territory, while others won't, depending on their location. Really odd, in my opinion.
Bill: The only stones that count are the ones that form the boundaries, and you don't count them. ;-)
Ellbur: This scoring system is highly unnatural: cutting points allowed, atari not allowed, some stones removed, some not.