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C-So! (シーソー) is a 1985 SG-1000 game developed by Compile and published by Sega. It is a port of an MSX game from the same year, which was published by Pony Canyon.
A South Korean company Joy Soft redundantly produced their own unlicensed "port" of the MSX version to the SG-1000 as well. 
The game has the player collect various items and defeat monsters by using see-saws. In order to progress, all items must be collected and all monsters must be destroyed. There is also an edit mode, allowing the player to create their own levels.