RE: A Discussion About CSS Reusability

/*******************/
/* Reset UA Styles */
/*******************/
html * {
    outline:none;
}
body, html {
    padding:0;
    margin:0;
    border:none;
    height:100%;
}
select, button, input, fieldset, label, legend, .no_appearance {
    -webkit-appearance:none;
    -moz-appearance:none;
    -o-appearance:none;
    -ms-appearance:none;
    border:none;
}
ul {
    margin:0;
    padding:0;
    list-style:none;
}
header, section, article, div, ul, li, nav, .border_box {
    box-sizing:border-box;
}
/*******************/
/* General Classes */
/*******************/
.flexbox_pack_center {
    -webkit-box-pack: center;
    -moz-box-pack: center;
    -o-box-pack: center;
    box-pack: center;
}
.flexbox_strech {
    -webkit-box-align: stretch;
    -moz-box-align: stretch;
    -o-box-align: stretch;
    box-align: stretch;
}
.flexbox_3 {
    -webkit-box-flex:3;
    -moz-box-flex:3;
    -o-box-flex:3;
    box-flex:3;
    display:block;
}
.flexbox_2 {
    -webkit-box-flex:2;
    -moz-box-flex:2;
    -ms-box-flex:2;
    -o-box-flex:2;
    box-flex:2;
    display:block;
}
.flexbox_1 {
    -webkit-box-flex:1;
    -moz-box-flex:1;
    -ms-box-flex:1;
    -o-box-flex:1;
    box-flex:1;
    display:block;
}
.flexbox_0 {
    -webkit-box-flex:0;
    -moz-box-flex:0;
    -ms-box-flex:0;
    -o-box-flex:0;
    box-flex:0;
    display:block;
}
.flexbox_vert {
    box-sizing:border-box;
    display:-webkit-flexbox;
    display:-webkit-box;
    display:-moz-box;
    display:-ms-box;
    display:-o-box;
    display:box;
    -webkit-box-orient:vertical;
    -moz-box-orient:vertical;
    -ms-box-orient:vertical;
    -o-box-orient:vertical;
    box-orient:vertical;
}
.flexbox {
    box-sizing:border-box;
    display:-webkit-flexbox;
    display:-webkit-box;
    display:-moz-box;
    display:-ms-box;
    display:-o-box;
    display:box;
}
/* Transitions */
.transition {
    -webkit-transition: all 0.3s ease-in-out;
    -moz-transition: all 0.3s ease-in-out;
    -o-transition: all 0.3s ease-in-out;
    transition: all 0.3s ease-in-out;
}
.transition_long {
    -webkit-transition: all 0.6s ease-in-out;
    -moz-transition: all 0.6s ease-in-out;
    -o-transition: all 0.6s ease-in-out;
    transition: all 0.6s ease-in-out;
}
/* State */
.centered_hor {
    position:absolute;
    left:0; right:0;
    margin:auto;
}
.centered_ver {
    position:absolute;
    top:0; bottom:0;
    margin:auto;
}
.centered {
    position:absolute;
    top:0; bottom:0;
    left:0; right:0;
    margin:auto;
}
.hidden {
    visibility:hidden !important;
    opacity:0 !important;
}
.shown {
    visibility:visible !important;
    opacity:1 !important;
}
/* General IDs */
#app_wrapper {
    position:absolute;
    top:0; left:0;
    bottom:0; right:0;
    height:100%;
    width:100%;
    overflow:hidden;
}