background-position: top center

allowed (50% from the left, 0% from the top, in this case vertical comes before horizontal)

[OK IF HERE]

10px top || 10px center || 10px bottom || 15% top || 15% center || 15% bottom || left 20px || center 20px || right 20px || 10px 50% || left 10% || center 5% || right 15% || center top || top center || center bottom || bottom center || right top || top right || left top || top left || right bottom || bottom right || left bottom || bottom left || 10px left || top 20% || 10px right || bottom 20% ||