* {
    margin: 0;
    padding: 0;
}

/*给每个块添加基础样式*/
[class*='col-'] {
    box-sizing: border-box;
    float: left;
    background-color: #eee;
    border: 1px solid #999;
    height: 50px;
    margin: 10px;
    font-size: 12px;
    text-align: center;
    line-height: 50px;
    
}

/*大于768px*/
@media (min-width: 769px) {
    .col-md-1 {
        width: calc( 8.3333% - 20px );
    }
    .col-md-2 {
        width: calc( 16.6666% - 20px );
    }
    .col-md-3 {
        width: calc( 25% - 20px );
    }
    .col-md-4 {
        width: calc( 33.3333% - 20px );
    }
    .col-md-6 {
        width: calc( 50% - 20px );
    }
}
/*小于768px*/
@media (max-width: 768px) {
    .col-sm-2 {
        width: calc( 16.6666% - 20px );
    }
    .col-sm-3 {
        width: calc( 25% - 20px );
    }
    .col-sm-6 {
        width: calc( 50% - 20px );
    }
    .col-sm-8 {
        width: calc( 66.6666% - 20px );
    }
    .col-sm-12 {
        width: calc( 100% - 20px );
    }
}