html
body
#app

*{
box-sizing: border-box
z-index: 10
}
body{
background gray
}

app {

position: relative
height: 100%
min-height: 100vh
background: white
max-width: 540px
margin: 0 auto
padding-bottom: 60px // 给footer留空，可不用
-webkit-font-smoothing antialiased
-moz-osx-font-smoothing grayscale
-webkit-tap-highlight-color: transparent
}