媒介查询和字体自动调整

html{
    font-size:10px;
    
}
@media only screen and (min-width:321px ) and (max-width:375px) {
    html{font-size:11px;}
}
@media only screen and (min-width:376px ) and (max-width:414px) {
    html{font-size:12px;}
}
@media only screen and (min-width:415px ) and (max-width:639px) {
    html{font-size:15px;}
}
@media only screen and (min-width:640px ) and (max-width:719px) {
    html{font-size:20px;}
}
@media only screen and (min-width:720px ) and (max-width:749px) {
    html{font-size:22.5px;}
}
@media only screen and (min-width:750px ) and (max-width:799px) {
    html{font-size:23.5px;}
}
@media only screen and (min-width:800px ){
    html{font-size:25px;}
}