背景

css demo

         background:green
       

         background:content-box radial-gradient(crimson, skyblue)
       

         background:url("https://interactive-examples.mdn.mozilla.net/media/examples/lizard.png") no-repeat
       

         background:left 5% / 15% 60% repeat-x url("../../media/examples/star.png")
       

         background-size:contain 
       

         background-size:cover
       

background-attachment
background-clip
background-color
background-image
background-origin
background-position
background-repeat
background-size