body, html {
  height: 100%;
  margin: 0;
  padding: 0;
  width: 100%;
}


body {
  display: flex;
  flex-direction: column;
}

html {
  background: url("../img/back.gif");
  background-size: 1000%;
  background-position: 33% 80%;
  font-family: monospace;
  font-size: 11pt;
  line-height: 1.2;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
}


/*----- MENU  ------------------------------------*/

.header {
  position: fixed;
  width: 100%;
  z-index: 1000;
}

.compo-wrapper {
  position: relative;
  flex: 1 0 auto;
  cursor: pointer;
}

.whitebox {
  background-color: white;
  padding: 8px;
}

.topbar {
  position: relative;
  z-index: 20;
}

.logo {
  display: block;
  height: 24px;
  width: auto;
}

.collapsible {
  position: absolute;
  transform: translateY(-110%); /* More than 100% to mask drop shadow */
  transition: transform 0.7s ease;
  z-index: 10;
  width: 100%;

  display: flex;
  flex-direction: row;
  box-sizing: border-box;
  box-shadow: 0 0 20px rgba(0,0,0,0.6);
  padding-top: 0.3em;

}
.header:hover .collapsible {
  transform: translateY(0);
}

.half {
  flex: 2 1 50%;
  padding-bottom: 30px;

}


.half:first-child {
  margin-right: 1vw;
}

.half:last-child {
  margin-left: 1vw;
}


.collapsible p {
  position: relative;
  top: 0.61vw; /* align text on baseline */
}

.collapsible p:first-child {
  margin-top: -0.61vw; /* to compensate baseline alignment */
}

.collapsible p:last-child {
  margin-bottom: 0;
}

.collapsible a.invisible {
  color: inherit;
  text-decoration: inherit;
}

::selection {
  background-color: rgba(0, 0, 0, 0.9);
  color: white;
}



/*----- MOBILE  -----------------------------------*/


.blurJP{
  display: none;
}
.mobilemessage{
  display: none;
}
.mobilemoji{
  display: none;
}

/*----- MOBILE VERTION -----------------------------------*/

@media screen and (max-width: 500px) {

  .image {display: none;}
  iframe{display: none;}
  .header{display: none;}
  overflow: {hidden;}

body{width: 100%;
border: 0;
top: 0px;
}

.blurJP{
  position:fixed;
  border: "0"
  top: 0px;
  height: 100%;
  border: 0;
  display: block;
  background-repeat: repeat;
  background-size: cover;
}
}
/*----- IMAGE  -----------------------------------*/

.image{

}
/*----- VIDEO  -----------------------------------*/

.video iframe {
  position: absolute;
  width: 100%;
  height: 100%;
}

.video{
  display: flex;
  position: relative;
  width:100%;
  height:0;
  margin: 0;
  z-index: 1;
}
<