A circle, a triangle and a square.
To some they are just geometric shapes, to those who have enjoyed "Squid Game" it is an invitation to a deadly game of survival.
Viewers worldwide are enjoying its vivid thrills, and it has topped FlixPatrol's "Top TV Shows on Netflix for several days.
What caught their eyes the most were the bizarre, fantastic sets that even mesmerized the actors.
"On the first day when we got to the film set, we were busy taking photos. It felt like we were in a dream."
Critics say the variety of hues and structures were prepared in a sophisticated way, all having certain messages behind them.
Stairs show how our lives can have ups and downs, and the venues where the games take place make the viewers look back on their own childhood.
"The playground rides make us think about the time when we were young. It has a variety of colors, as if they teach us we should respect diversity. Also it tells us that we can solve problems if we stick to basic principles."
"Another reason for its popularity is that each round of deaths is based on a popular Korean schoolyard game from the 1970s and ‘80s.
"Red light, green light."
The kids' games take the brutality to another level of shock and horror.”
The simple rules of the games let watchers overseas follow the story with ease.
For "Red light, Green light", participants just have to move forward while "it" shouts out the phrase, and should stay still when "it" is watching.
"Ddakji " isn't difficult either.
Players simply try to flip over their opponent's paper tile which is called "ddakji" in Korean.
"The survival game concept is familiar to everyone, but "Squid Game" distinguished itself by using Korea's own games."
Last but not least, there are scenes telling us that humanity is the most important thing, even when people are playing the murderous games.
Those human elements such as making "kkanbu" would have touched viewers' minds amid the violence.
Kim Bo-kyoung, Arirang News.