Surface stain

A tile holds one stain at a time. Feet and paws track mud indoors from unpaved ground or leave wet patches after rain or contact with water. Fire leaves ash, sick settlers leave vomit and bleeding units leave blood. Walking through mud, water, blood or vomit temporarily lowers mood. Repeated exposure makes the penalty worse, especially for vomit. Ash has no direct mood effect. Every indoor stain lowers room luxury until it disappears or is cleaned. Stains fade faster outdoors and in rain.