A Heating / Cooling switch: the icon morphs flame to snowflake, the colour follows, and the services and prices swap in place.
Use it for: HVAC first; also pool (open / close), landscaping (summer / winter), gutters and roofing (storm season). When: A business whose offer really changes by season. It opens on the season it is now (local month). Don't: More than two states, or hiding the off-season prices from search (both panels stay in the HTML). How: MorphSVG tweens one path between the two icons; both panels share one grid cell so the box never changes height; the hidden panel is inert. Without JS both show, stacked. Weight: 1.8 KB gzipped (our CSS + JS) + GSAP from jsDelivr: GSAP core 28.3 + MorphSVG 9.6 KB gzipped (shared by every effect on the page). Plugins: MorphSVG.