This kind of series is new for a Korean series, but nothing special in it.
Japanese has a lot series that has a plot like this such as liar game, as the god says, Alice in borderland and the list goes on and on.
As for western one we have Saw, Hunger games, Maze runner (maybe ?). and so on.
I get that the director want to picture how adult play like a kid for fortune in cost of a person life in a very realistic way. but they have no idea of what kind of game they should play, so they choose to copy it from any other series with a little bit changes. here is my break down.

First gathering :
everyone sent to the game with their own consent by calling the number from the invitation number yet still asks "why should we trust you ?". really ? wtf ? you should've ask that before give your consent on the phone. AND surprisingly nobody asked "what will happened if i lost the game ?"

1st game Red/Green light game :
70 %+ of the scene copy pasted from as the god says. first they gathered the player, when the game started some random people gave zero shit about the condition and just play the game and get killed. after that everyone scared and scream and the game field become a massacre field, then a 4 eyed smart guy that get a trick to beat the game and save the day .the first game is the best example of copying and rephrasing a bit of your friends homework, good job Mr.director.

Second gathering & game restart:
everything f up. everybody scared, half of the participator want to go home and try to make a vote to stop the game, which supposed to be happened in the first gathering but no lets just vote after everyone is dead. realistic my ass.

2nd game The sugar cookie game:
I cant even call it a game, but okay lets just call it a game, everyone solving it with a brute force method nobody use their brain except for the MC and the noisy crazy girl. very realistic indeed. but at least it came from Korean culture which makes it unique I will give this game some point.

Night time war :
They changed from "game" concept to "survival" . people start kill each other just to win. the plot hole is nobody know that time that there will be only one winner or even they wont know if killing each other will make the game easier/faster

3rd game Tug of war:
Decent game not very unique, no Korean culture included. this game is just an easy answer for "what should we play next. the trick to beat the game is ridiculous. I get that they want to picture brain over brawns. but did they actually did a research about this ?.

The cheating mess and the police investigation :
this plot used for season 2 possibilities. in my opinion its too weak considering how its end.

4th game marbles :
Also a decent game, and an easy option, but they give some Korean culture in here so the game is pretty much unique because you can play however you want. and i love how the characters grow here. the mc who neglect his mother start to care for the elderly more, the 4 eyed guy that struggle to keep his sanity losing his shit, and the girl who lost trust in people found start to trust someone.

5th game The stepping glass game :
I'm not Korean but I'm sure I've seen somewhere about Kids hearing old story about knocking the stone before you step to make sure its safe. so some culture included but surprisingly nobody does that until the last guy that know something abt the glasses. nobody even try to check the step with whatever they bring such as jacket/clothes or anything that can be used. nobody use their brain, where did the "brain over brawls" go from 3rd game ?.

3 last survivor :
I love this one. it pictures how they change after all of the game. the selfish girl became a pure hearted girl, the selfish gamble addict guy became a very caring guy, and the prodigy 4 eyed losing his shit

Last game, Squid game:
No game explanation, as a non-Korean I just see it like a 2 guy fist to fist fight. no meaning, no culture, nothing. ironic considering squid game is the title yet it was the worst game in the series.

The winner :
the after game , messed up mc losing his shit. classic drama. not bad, but not good either.

Conclusion :
A great potential series with a lot of "but" and " it could be better". not a very interesting series, I found myself fall asleep out of boredom few times. I don't know most of the actor/actresses, but i think they are good since i like how they potray the change of the characters during/after the game. None of the music stuck i my ears or get into my daily playlist, not the song/singer is bad is just the song choices for the theme or placements could have been better.
worth the watch ?. yes if you just want to Netflix and chill and love this kind of genre, no if you want to watch a really interesting psycho series.