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Well this guy plans to make one, but his deviantart is pretty quiet the last months which means he either really focus on his game or it's dead before it even left the alpha stage.
Magnusmagneto is already mentioned by you, but he plans to make even more games which is actually a big drawback right now. i think he works at around 3 games at once while also writing fmg stories including even voiced ones.
He also had personal problems regarding his fetish, but according to a blog on his deviantart he seems to make peace with it.
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Here is a demo of his other big game project and he also wrote short stories which build up to this game., but too be honest don't get too exited with this guy.
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This one is probaly the most promising of all games involving buff girls. Two short demos were already released and that artist is in general really reliable regarding his work.
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They also have a very active discord which talks both about the game and basicly anything involving female muscles in general.
There are also a few games which only involve muscle girls without growth but you only asked for fmg.
I could search and list them too if you want.
So yeah i think i have basicly covered all big projects which were not mentioned yet in this thread.
Hell buff females in general is already a niche fetish, because a lot of people treat it as an attack on their masculinity.
Even outlines of abs muscles on girls seems to be already huge turnoff for many when you look at this site and others. For example a lot of people are bothered in that something unlimited game because the artist choose to put a bit more flesh on wonderwoman, superwoman and galatea on them which make them stand out compared to all the super model or well teenage builds of the rest of the cast.
Sometimes i have the feeling we muscle lovers are grouped up with scat, vore, guro, unbirth and other messed up fetishes fans which is why that magnus guy took over a half year break to deal with it.
Personally i would put us on the same level as furries, futa or oversized breast/ass lovers.