Simple Grid Stylesheet using Flex

simple-grid.css

/*
GRID.CSS
Desc: Simple Grid Stylesheet
Author:Nik Mirza
Email: nik96mirza(at)gmail(dot)com
*/

html,body,div {
  -webkit-box-sizing: border-box; /* Safari/Chrome, other WebKit */
  -moz-box-sizing: border-box;    /* Firefox, other Gecko */
  box-sizing: border-box;         /* Opera/IE 8+ */
  margin:0;

  font-family: Verdana,sans-serif;
  font-size: 15px;
  line-height: 1.5;
}

/* Rows and column */
.row {
  display: -webkit-flex;
  display: flex;
  -webkit-flex-direction: row;
  flex-direction: row;
}

.row-wrap {
  -webkit-flex-wrap: wrap;
  flex-wrap: wrap;
}

.row-top {
  -webkit-align-items: flex-start;
  align-items: flex-start;
}

.row-bottom {
  -webkit-align-items: flex-end;
  align-items: flex-end;
}

.row-left {
  -webkit-justify-content: flex-start;
  justify-content: flex-start;
}

.row-right {
  -webkit-justify-content: flex-end;
  justify-content: flex-end;
}

.row-center-horizontal {
  -webkit-justify-content: center;
  justify-content: center;
}

.row-center-vertical {
  -webkit-align-items: center;
  align-items: center;
}

.column {
  display: -webkit-flex;
  display: flex;
  -webkit-flex-direction: column;
  flex-direction: column;
}

.grid-center {
  margin:auto;
}

.grid {
}

.grid-1 {
  width:100%;
}

.grid-1-2 {
  width:50%;
}

.grid-1-3 {
  width:33.33%;
}

.grid-2-3 {
  width:66.66%;
}

.grid-1-4 {
  width:25%;
}

.grid-3-4 {
  width:75%;
}

.grid-1-5 {
  width:20%;
}

.grid-2-5 {
  width:40%;
}

.grid-3-5 {
  width:60%;
}

.grid-4-5 {
  width:80%;
}

@media (max-width: 768px) {

  *[class*="row"] {
    -webkit-flex-direction: column;
    flex-direction: column;
  }

  *[class*="grid"] {
    width:100%;
  }
}

/* Dropdown menu */
.dropdown {
    position: relative;
    display: inline-block;
}

.dropdown-content {
    display: none;
    position: absolute;
    background-color: #f9f9f9;
    min-width: 160px;
    box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
    padding: 12px 16px;
    z-index: 1;
}

.dropdown:hover .dropdown-content {
    display: block;
}