Tatami

Tatami (畳) are soft mats used as flooring material in traditional Japanese-style rooms.

They are made in standard sizes, twice as long as wide, about 0.9 by 1.8 metres (3 by 6 ft), depending on the region.

[1] Tatami are covered with a weft-faced weave of soft rush (藺草, igusa) on a warp of hemp or weaker cotton.

[2][3] The term tatami is derived from the verb tatamu (畳む), meaning 'to fold' or 'to pile'.

[6] In the Kamakura period, there arose the shoin-zukuri architectural style of residence for the samurai and priests who had gained power.

'spread out for sitting', and rules concerning seating and etiquette determined the arrangement of the tatami in the rooms.

[7] Tatami were gradually popularized and reached the homes of commoners toward the end of the 17th century.

[11] It is NP-complete to determine whether a large room has an auspicious arrangement using only full mats.