Base Responsive Flex CSS Without Bootstrap

base.css

* {
    padding: 0;
    margin: 0;
    box-sizing: border-box;
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
}
.row {
    margin: 0 -1rem;
    display:flex;
    flex-wrap: wrap;
}
.row + .row {
    margin-top: 1rem;
}
[class*='col-'] {
    padding: 0 1rem;
}
.container {
    width: 100%;
    padding: 0 1rem;
    margin: 0 auto;
}
.mx-auto {
    margin: 0 auto;
}


.col-1 { flex: none; width: calc(100% * 1 / 12) }
.col-2 { flex: none; width: calc(100% * 2 / 12) }
.col-3 { flex: none; width: calc(100% * 3 / 12) }
.col-4 { flex: none; width: calc(100% * 4 / 12) }
.col-5 { flex: none; width: calc(100% * 5 / 12) }
.col-6 { flex: none; width: calc(100% * 6 / 12) }
.col-7 { flex: none; width: calc(100% * 7 / 12) }
.col-8 { flex: none; width: calc(100% * 8 / 12) }
.col-9 { flex: none; width: calc(100% * 9 / 12) }
.col-10 { flex: none; width: calc(100% * 10 / 12) }
.col-11 { flex: none; width: calc(100% * 11 / 12) }
.col-12 { flex: none; width: calc(100% * 12 / 12) }


@media screen and (min-width: 554px) {
    .col-xs-1 { flex: none; width: calc(100% * 1 / 12); }
    .col-xs-2 { flex: none; width: calc(100% * 2 / 12); }
    .col-xs-3 { flex: none; width: calc(100% * 3 / 12); }
    .col-xs-4 { flex: none; width: calc(100% * 4 / 12); }
    .col-xs-5 { flex: none; width: calc(100% * 5 / 12); }
    .col-xs-6 { flex: none; width: calc(100% * 6 / 12); }
    .col-xs-7 { flex: none; width: calc(100% * 7 / 12); }
    .col-xs-8 { flex: none; width: calc(100% * 8 / 12); }
    .col-xs-9 { flex: none; width: calc(100% * 9 / 12); }
    .col-xs-10 { flex: none; width: calc(100% * 10 / 12); }
    .col-xs-11 { flex: none; width: calc(100% * 11 / 12); }
    .col-xs-12 { flex: none; width: calc(100% * 12 / 12); }
}
@media screen and (min-width: 640px) {
    .container {
        max-width: 640px;
    }
    .col-sm-1 { flex: none; width: calc(100% * 1 / 12); }
    .col-sm-2 { flex: none; width: calc(100% * 2 / 12); }
    .col-sm-3 { flex: none; width: calc(100% * 3 / 12); }
    .col-sm-4 { flex: none; width: calc(100% * 4 / 12); }
    .col-sm-5 { flex: none; width: calc(100% * 5 / 12); }
    .col-sm-6 { flex: none; width: calc(100% * 6 / 12); }
    .col-sm-7 { flex: none; width: calc(100% * 7 / 12); }
    .col-sm-8 { flex: none; width: calc(100% * 8 / 12); }
    .col-sm-9 { flex: none; width: calc(100% * 9 / 12); }
    .col-sm-10 { flex: none; width: calc(100% * 10 / 12); }
    .col-sm-11 { flex: none; width: calc(100% * 11 / 12); }
    .col-sm-12 { flex: none; width: calc(100% * 12 / 12); }
}
@media screen and (min-width: 768px) {
    .container {
        max-width: 768px;
    }
    .col-md-1 { flex: none; width: calc(100% * 1 / 12) }
    .col-md-2 { flex: none; width: calc(100% * 2 / 12) }
    .col-md-3 { flex: none; width: calc(100% * 3 / 12) }
    .col-md-4 { flex: none; width: calc(100% * 4 / 12) }
    .col-md-5 { flex: none; width: calc(100% * 5 / 12) }
    .col-md-6 { flex: none; width: calc(100% * 6 / 12) }
    .col-md-7 { flex: none; width: calc(100% * 7 / 12) }
    .col-md-8 { flex: none; width: calc(100% * 8 / 12) }
    .col-md-9 { flex: none; width: calc(100% * 9 / 12) }
    .col-md-10 { flex: none; width: calc(100% * 10 / 12) }
    .col-md-11 { flex: none; width: calc(100% * 11 / 12) }
    .col-md-12 { flex: none; width: calc(100% * 12 / 12) }
}
@media screen and (min-width: 1024px)  {
    .container {
        max-width: 1024px;
    }
    .col-lg-1 { flex: none; width: calc(100% * 1 / 12) }
    .col-lg-2 { flex: none; width: calc(100% * 2 / 12) }
    .col-lg-3 { flex: none; width: calc(100% * 3 / 12) }
    .col-lg-4 { flex: none; width: calc(100% * 4 / 12) }
    .col-lg-5 { flex: none; width: calc(100% * 5 / 12) }
    .col-lg-6 { flex: none; width: calc(100% * 6 / 12) }
    .col-lg-7 { flex: none; width: calc(100% * 7 / 12) }
    .col-lg-8 { flex: none; width: calc(100% * 8 / 12) }
    .col-lg-9 { flex: none; width: calc(100% * 9 / 12) }
    .col-lg-10 { flex: none; width: calc(100% * 10 / 12) }
    .col-lg-11 { flex: none; width: calc(100% * 11 / 12) }
    .col-lg-12 { flex: none; width: calc(100% * 12 / 12) }
}
@media screen and (min-width: 1280px) {
    .container {
        max-width: 1280px;
    }
    .col-xl-1 { flex: none; width: calc(100% * 1 / 12) }
    .col-xl-2 { flex: none; width: calc(100% * 2 / 12) }
    .col-xl-3 { flex: none; width: calc(100% * 3 / 12) }
    .col-xl-4 { flex: none; width: calc(100% * 4 / 12) }
    .col-xl-5 { flex: none; width: calc(100% * 5 / 12) }
    .col-xl-6 { flex: none; width: calc(100% * 6 / 12) }
    .col-xl-7 { flex: none; width: calc(100% * 7 / 12) }
    .col-xl-8 { flex: none; width: calc(100% * 8 / 12) }
    .col-xl-9 { flex: none; width: calc(100% * 9 / 12) }
    .col-xl-10 { flex: none; width: calc(100% * 10 / 12) }
    .col-xl-11 { flex: none; width: calc(100% * 11 / 12) }
    .col-xl-12 { flex: none; width: calc(100% * 12 / 12) }
}
@media screen and (min-width: 1536px) {
    .container {
        max-width: 1536px;
    }
    .col-xxl-1 { flex: none; width: calc(100% * 1 / 12) }
    .col-xxl-2 { flex: none; width: calc(100% * 2 / 12) }
    .col-xxl-3 { flex: none; width: calc(100% * 3 / 12) }
    .col-xxl-4 { flex: none; width: calc(100% * 4 / 12) }
    .col-xxl-5 { flex: none; width: calc(100% * 5 / 12) }
    .col-xxl-6 { flex: none; width: calc(100% * 6 / 12) }
    .col-xxl-7 { flex: none; width: calc(100% * 7 / 12) }
    .col-xxl-8 { flex: none; width: calc(100% * 8 / 12) }
    .col-xxl-9 { flex: none; width: calc(100% * 9 / 12) }
    .col-xxl-10 { flex: none; width: calc(100% * 10 / 12) }
    .col-xxl-11 { flex: none; width: calc(100% * 11 / 12) }
    .col-xxl-12 { flex: none; width: calc(100% * 12 / 12) }
}