Keep this exact 64x64 pixel canvas and the existing quiet...

Keep this exact 64x64 pixel canvas and the existing quiet muted cement ground colors unchanged. Add only one low-contrast old concrete expansion joint horizontally across y=31 from x=0 to x=63. Joint is one dark gray-brown pixel wide, two tiny irregular chipped notches at x=18 and x=45, no grass, no stones, no white highlights. Top and bottom remain the exact existing uniform ground. Make the left and right ends join seamlessly when repeated horizontally. It is a top-down village lane boundary tile, not a wall or raised curb. All detail restricted to rows y=27..36. Hard native pixel edges, no gradient, no new scene, no perspective change.