style.css

body {
  margin: auto 0;
}

.zone {
    /* padding:30px 50px;
    margin:40px 60px; */
    cursor:pointer;
    /* display:inline-block; */
    color:#FFF;
    font-size:2em;
    border-radius:4px;
    border:1px solid #bbb;
    transition: all 0.3s linear;
}

.zone:hover {
    -webkit-box-shadow:rgba(0,0,0,0.8) 0px 5px 15px, inset rgba(0,0,0,0.15) 0px -10px 20px;
    -moz-box-shadow:rgba(0,0,0,0.8) 0px 5px 15px, inset rgba(0,0,0,0.15) 0px -10px 20px;
    -o-box-shadow:rgba(0,0,0,0.8) 0px 5px 15px, inset rgba(0,0,0,0.15) 0px -10px 20px;
    box-shadow:rgba(0,0,0,0.8) 0px 5px 15px, inset rgba(0,0,0,0.15) 0px -10px 20px;
}

.box:hover {
    -webkit-transform:rotate(-7deg);
    -moz-transform:rotate(-7deg);
    -o-transform:rotate(-7deg);
    transform:rotate(-7deg);
}

/* cover */
.container {
  display: flex;
  align-items: center;
  justify-content: center;
  height: 50vh;
}

.cover {
  width: 30rem;
}

/* grid */
.grid-wrapper {
  display: grid;
  gap: 20px;
  grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
}

.box > img {
  width: 100%;
}

.box {
  background-color: #444;
  padding: 130px;
  margin: 20px;
}


/* navbar */

.sticky {
  position: fixed;
  top: 0;
  width: 100%;
}

.main-nav {
  display: flex;
  list-style: none;
  font-size: 0.7em;
  margin: 0;
}


@media only screen and (max-width: 600px) {
  .main-nav {
    font-size: 0.5em;
    padding: 0;
  }
}

li {
  padding: 20px;
}

.push {
  margin-left: auto;
}

a {
  color: #F5F5F6;
  text-decoration: none;
}

/* footer */
footer {
  text-align: center;
}

/*https://paulund.co.uk/how-to-create-shiny-css-buttons*/
/***********************************************************************
 *  Green Background
 **********************************************************************/
.green{
    background: #56B870; /* Old browsers */
    background: -moz-linear-gradient(top, #56B870 0%, #a5c956 100%); /* FF3.6+ */
    background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#56B870), color-stop(100%,#a5c956)); /* Chrome,Safari4+ */
    background: -webkit-linear-gradient(top, #56B870 0%,#a5c956 100%); /* Chrome10+,Safari5.1+ */
    background: -o-linear-gradient(top, #56B870 0%,#a5c956 100%); /* Opera 11.10+ */
    background: -ms-linear-gradient(top, #56B870 0%,#a5c956 100%); /* IE10+ */
    background: linear-gradient(top, #56B870 0%,#a5c956 100%); /* W3C */
}

/***********************************************************************
 *  Red Background
 **********************************************************************/
.red{
    background: #C655BE; /* Old browsers */
    background: -moz-linear-gradient(top, #C655BE 0%, #cf0404 100%); /* FF3.6+ */
    background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#C655BE), color-stop(100%,#cf0404)); /* Chrome,Safari4+ */
    background: -webkit-linear-gradient(top, #C655BE 0%,#cf0404 100%); /* Chrome10+,Safari5.1+ */
    background: -o-linear-gradient(top, #C655BE 0%,#cf0404 100%); /* Opera 11.10+ */
    background: -ms-linear-gradient(top, #C655BE 0%,#cf0404 100%); /* IE10+ */
    background: linear-gradient(top, #C655BE 0%,#cf0404 100%); /* W3C */
}

/***********************************************************************
 *  Yellow Background
 **********************************************************************/
.yellow{
    background: #F3AAAA; /* Old browsers */
    background: -moz-linear-gradient(top, #F3AAAA 0%, #febf04 100%); /* FF3.6+ */
    background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#F3AAAA), color-stop(100%,#febf04)); /* Chrome,Safari4+ */
    background: -webkit-linear-gradient(top, #F3AAAA 0%,#febf04 100%); /* Chrome10+,Safari5.1+ */
    background: -o-linear-gradient(top, #F3AAAA 0%,#febf04 100%); /* Opera 11.10+ */
    background: -ms-linear-gradient(top, #F3AAAA 0%,#febf04 100%); /* IE10+ */
    background: linear-gradient(top, #F3AAAA 0%,#febf04 100%); /* W3C */
}

/***********************************************************************
 *  Blue Background
 **********************************************************************/
.blue{
    background: #7abcff; /* Old browsers */
    background: -moz-linear-gradient(top, #7abcff 0%, #60abf8 44%, #4096ee 100%); /* FF3.6+ */
    background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#7abcff), color-stop(44%,#60abf8), color-stop(100%,#4096ee)); /* Chrome,Safari4+ */
    background: -webkit-linear-gradient(top, #7abcff 0%,#60abf8 44%,#4096ee 100%); /* Chrome10+,Safari5.1+ */
    background: -o-linear-gradient(top, #7abcff 0%,#60abf8 44%,#4096ee 100%); /* Opera 11.10+ */
    background: -ms-linear-gradient(top, #7abcff 0%,#60abf8 44%,#4096ee 100%); /* IE10+ */
    background: linear-gradient(top, #7abcff 0%,#60abf8 44%,#4096ee 100%); /* W3C */
}