What are the yellow traditional Korean floors made of?

I’m not sure if it is the same as tatami mats which is made from rice straw.
Tatamis are Japanese but I imagine that many of the Asian cultures share some similar items only call them something esle. Also the style may be different or the material.
But it is the only thing I can think of that is soft, and springy, hard and yellow.
Really fresh and young it starts of green but the older ones are usually yellow to a pale yellow.

Tatami is definitely Japanese, that is not what they use in Korea. Best information I have found so far in researching this:

In Korea, they captured heat generated from cooking and called it an Ondol. An Ondol was made up of three parts: a stove or fireplace, a chimney, and horizontal flues under the flooring. On top of the flue system was a thick, flat stone called a Kudul and on top of the Kadul was flattened yellow soil topped with rice paper. And so, the Kadul became warm as a result of the heat passing through the flues under the flooring.

Thank you for your answers.

They are not tatami because the flooring is solid.

The heating system is Ondol, but does not tell me what the flooring is, or how it feels underfoot.

Here’s hoping someone who is Korean or has visited will answer.

On top of the flue system was a thick, flat stone called a Kudul and on top of the Kadul was flattened yellow soil topped with rice paper.