Clean friendly science infographic for children and classrooms, explaining why Lidong, the winter-beginning solar term, arrives as Earth moves along its orbit. Top center a large tilted Earth globe with a small sun in the upper left, a pale elliptical orbit path curving across the page, and four small Earth positions marking spring equinox, summer solstice, autumn equinox and Lidong. Below, three rounded panels in a row: the first shows sunlight hitting the Northern Hemisphere at a low slanting angle, the second shows the Northern Hemisphere tilted away from the sun, the third shows shorter days and longer nights with a small clock icon. Soft blue and warm amber palette, flat vector illustration style, clean white background, short readable English labels only, no paragraphs, no watermark, 3:2 landscape composition.