HTML CSS JSResult
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body {
  background-color: #333;
  padding: 1.25em; /* 20 */
}
ul {
    padding: 0;
}
ul, li {
  list-style: none;
}
a {
  
  text-decoration: none;
}
#nav_a {
  
  position: relative;
 
  left: 0%;
  z-index: 990;
  
}
.navi_panel{
    width: 100%;
}
#nav_a > a {
  display: none;
}
#nav_a li {
  position: relative;
}
#nav_a li a {
  color: #fff;
  display: block;
  font-size: 1.0em !important;
}
#nav_a li a:active {
  background-color: #c00 !important;
}
#nav_a span:after {
  width: 0;
  height: 0;
  border: 0.313em solid transparent; /* 5 */
    border-bottom: none;
    border-top-color: #34BAFF;
    content: '';
    vertical-align: middle;
    display: inline-block;
    position: relative;
    right: -0.313em; /* 5 */
}
/* first level */
#nav_a > ul {
    height: 3em; /* 60 */
    background-color: #000000;
}
#nav_a > ul > li {
    width: 20%;
    height: 100%;
    float: left;
}
#nav_a > ul > li > a {
    height: 100%;
    font-size: 1.2em; /* 24 */
    line-height: 2.5em; /* 60 (24) */
    text-align: center;
}
#nav_a > ul > li:not( :last-child ) > a {
    border-right: 1px solid #555;
}
#nav_a > ul > li:hover > a,
#nav_a > ul:not( :hover ) > li.active > a {
    background-color: #555;
}
/* second level */
#nav_a li ul {
    background-color: #555;
    display: none;
    position: absolute;
    top: 100%;
}
#nav_a li:hover ul {
    display: block;
    left: 0;
    right: 0;
}
#nav_a li:not( :first-child ):hover ul {
    left: -1px;
}
#nav_a li ul a {
    font-size: 1.25em; /* 20 */
    border-top: 1px solid #333333;
    padding: 0.5em; /* 15 (20) */
}
#nav_a li ul li a:hover,
#nav_a li ul:not( :hover ) li.active a {
    background-color: #555555;
}
@media only screen and ( max-width: 62.5em ) { /* 1000 */
    #nav_a {
        width: 100%;
        position: static;
        margin: 0;
    }
}
@media only screen and ( max-width: 40em ) /* 640 */
{
    html {
        font-size: 75%; /* 12 */
    }
    #nav_a {
        position: relative;
        top: auto;
        left: auto;
    }
    #nav_a > a {
        width: 3.125em; /* 50 */
        height: 3.125em; /* 50 */
        text-align: left;
        text-indent: -9999px;
        background-color: #e15a1f;
        position: relative;
    }
    #nav_a > a:before,
    #nav_a > a:after {
        position: absolute;
        border: 2px solid #fff;
        top: 35%;
        left: 25%;
        right: 25%;
        content: '';
    }
    #nav_a > a:after {
        top: 60%;
    }
    #nav_a:not( :target ) > a:first-of-type,
    #nav_a:target > a:last-of-type {
        display: block;
    }
    /* first level */
    #nav_a > ul {
        height: auto;
        display: none;
        position: absolute;
        left: 0;
        right: 0;
    }
    #nav_a:target > ul {
        display: block;
    }
    #nav_a > ul > li {
        width: 100%;
        float: none;
    }
    #nav_a > ul > li > a {
        height: auto;
        text-align: left;
        padding: 0 0.833em; /* 20 (24) */
    }
    #nav_a > ul > li:not( :last-child ) > a {
        border-right: none;
        border-bottom: 1px solid #cc470d;
    }
    /* second level */
    #nav_a li ul {
        position: static;
        padding: 1.25em; /* 20 */
        padding-top: 0;
    }
}