Some games come in .gg format but are in fact SMS games. Rename the .gg extention to .sms or .bin to fix them.
These games are mostly listed in this page SMSpower-SMS-GG list.
The "Aspect ratio" doesn't do much in PAL mode, that's normal
The "Region" parameter toggle some hardware features that are specific to the different console models.
Some localized games need these modifications to work properly
The "Masked left column" option controls behaviour of left column when hidden by system (usually during horizontal
scrolling). "BG" sets it to the background/overscan colour, as on original hardware. "Black" makes it black,
which may look better on non full-screen settings as the column will blend in with surrounding black area.
"Cut" will remove the column from the active image, so the horizontal resolution becomes 248 instead of 256. This
will distort the image when scaled, particularly on integer scaling settings, but will use more of the screen.
When "Border" is set to "Yes" the left column is always shown as part of the border, so "Masked left column" is
disabled.
Each game cartridge comes with a specific mapper, which description is not included in the .gg ou .sms file.
The core has a special logic to automatically determine which mapper needs to be used, but some games make
a good effort to make this logic fail. The "Disable mappers" parameter permits to force the usage
of the most used sega mapper.
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