Impermanence is a strong theme in traditional Japanese dwellings. The size of rooms can be altered by interior sliding walls or screens, the already mentioned "shōji". Cupboards built smoothly into the wall hide futon, mattresses pulled out before going to bed, allowing more space to be available during the day. The versatility of these dwellings becomes more apparent with changes of seasons. In summer, for example, exterior walls can be opened to bring the garden and cooling breezes in. The minimal decoration also alters seasonally, with a different scroll hanging or new flower arrangement.