<div class="cotn_principal">
<div class="cont_centrar">

  <div class="cont_login">
<div class="cont_info_log_sign_up">
  <div class="col_md_login">
<div class="cont_ba_opcitiy">
   
  <h2>LOGIN</h2>  
  <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p>  
  <button class="btn_login" onclick="cambiar_login()">LOGIN</button>
  </div>
  </div>
<div class="col_md_sign_up">
<div class="cont_ba_opcitiy">
  <h2>SIGN UP</h2>

   
  <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p>

  <button class="btn_sign_up" onclick="cambiar_sign_up()">SIGN UP</button>
</div>
  </div>
  </div>

   
  <div class="cont_back_info">
  <div class="cont_img_back_grey">
  <img src="https://images.unsplash.com/42/U7Fc1sy5SCUDIu4tlJY3_NY_by_PhilippHenzler_philmotion.de.jpg?ixlib=rb-0.3.5&q=50&fm=jpg&crop=entropy&s=7686972873678f32efaf2cd79671673d" alt="" />
  </div>
   
  </div>
<div class="cont_forms" >
  <div class="cont_img_back_">
  <img src="https://images.unsplash.com/42/U7Fc1sy5SCUDIu4tlJY3_NY_by_PhilippHenzler_philmotion.de.jpg?ixlib=rb-0.3.5&q=50&fm=jpg&crop=entropy&s=7686972873678f32efaf2cd79671673d" alt="" />
  </div>
  <div class="cont_form_login">
<a href="#" onclick="ocultar_login_sign_up()" ><i class="material-icons"></i></a>
  <h2>LOGIN</h2>
  <input type="text" placeholder="Email" />
<input type="password" placeholder="Password" />
<button class="btn_login" onclick="cambiar_login()">LOGIN</button>
  </div>
   
  <div class="cont_form_sign_up">
<a href="#" onclick="ocultar_login_sign_up()"><i class="material-icons"></i></a>
  <h2>SIGN UP</h2>
<input type="text" placeholder="Email" />
<input type="text" placeholder="User" />
<input type="password" placeholder="Password" />
<input type="password" placeholder="Confirm Password" />
<button class="btn_sign_up" onclick="cambiar_sign_up()">SIGN UP</button>

  </div>

  </div>
   
  </div>
  </div>
</div>

/* ------------------------------------ Click on login and Sign Up to changue and view the effect
---------------------------------------
*/

* {
  margin: 0px auto;
  padding: 0px;
  text-align: center;
  font-family: 'Open Sans', sans-serif;
}

.cotn_principal {
  position: absolute;
  width: 100%;
  height: 100%;
/* Permalink - use to edit and share this gradient: http://colorzilla.com/gradient-editor/#cfd8dc+0,607d8b+100,b0bec5+100 */
background: #cfd8dc; /* Old browsers */
background: -moz-linear-gradient(-45deg, #cfd8dc 0%, #607d8b 100%, #b0bec5 100%); /* FF3.6-15 */
background: -webkit-linear-gradient(-45deg, #cfd8dc 0%,#607d8b 100%,#b0bec5 100%); /* Chrome10-25,Safari5.1-6 */
background: linear-gradient(135deg, #cfd8dc 0%,#607d8b 100%,#b0bec5 100%); /* W3C, IE10+, FF16+, Chrome26+, Opera12+, Safari7+ */
filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#cfd8dc', endColorstr='#b0bec5',GradientType=1 ); /* IE6-9 fallback on horizontal gradient */

}

.cont_centrar {
  position: relative;
  float: left;
  width: 100%;
}

.cont_login {
  position: relative;
  width: 640px;
left: 50%;
margin-left: -320px;
   
}

.cont_back_info {  
position: relative;
  float: left;
  width: 640px;
  height: 280px;
overflow: hidden;
  background-color: #fff;
  margin-top: 100px;
box-shadow: 1px 10px 30px -10px rgba(0,0,0,0.5);
}

.cont_forms {
  position: absolute;
  overflow: hidden;
  top:100px;
left: 0px;
  width: 320px;
  height: 280px;
  background-color: #eee;
-webkit-transition: all 0.5s;
-moz-transition: all 0.5s;
-ms-transition: all 0.5s;
-o-transition: all 0.5s;
transition: all 0.5s;
}

.cont_forms_active_login {
box-shadow: 1px 10px 30px -10px rgba(0,0,0,0.5);
  height: 420px;  
top:20px;
left: 0px;
  -webkit-transition: all 0.5s;
-moz-transition: all 0.5s;
-ms-transition: all 0.5s;
-o-transition: all 0.5s;
transition: all 0.5s;

}

.cont_forms_active_sign_up {
box-shadow: 1px 10px 30px -10px rgba(0,0,0,0.5);
  height: 420px;  
top:20px;
left:320px;
-webkit-transition: all 0.5s;
-moz-transition: all 0.5s;
-ms-transition: all 0.5s;
-o-transition: all 0.5s;
transition: all 0.5s;
}

.cont_img_back_grey {
  position: absolute;
  width: 950px;
top:-80px;
  left: -116px;
}

.cont_img_back_grey > img {
  width: 100%;
  -webkit-filter: grayscale(100%); filter: grayscale(100%);
opacity: 0.2;
animation-name: animar_fondo;
  animation-duration: 20s;
animation-timing-function: linear;
animation-iteration-count: infinite;
animation-direction: alternate;

}

.cont_img_back_ {
  position: absolute;
  width: 950px;
top:-80px;
  left: -116px;
}

.cont_img_back_ > img {
  width: 100%;
opacity: 0.3;
animation-name: animar_fondo;
animation-duration: 20s;
animation-timing-function: linear;
animation-iteration-count: infinite;
animation-direction: alternate;
}

.cont_forms_active_login > .cont_img_back_ {
top:0px;  
  -webkit-transition: all 0.5s;
-moz-transition: all 0.5s;
-ms-transition: all 0.5s;
-o-transition: all 0.5s;
transition: all 0.5s;
}

.cont_forms_active_sign_up > .cont_img_back_ {
top:0px;  
left: -435px;
  -webkit-transition: all 0.5s;
-moz-transition: all 0.5s;
-ms-transition: all 0.5s;
-o-transition: all 0.5s;
transition: all 0.5s;
}
   

.cont_info_log_sign_up {
position: absolute;
  width: 640px;
  height: 280px;
  top: 100px;
z-index: 1;
}  

.col_md_login {
  position: relative;
  float: left;
  width: 50%;
}

.col_md_login > h2 {
  font-weight: 400;
margin-top: 70px;
  color: #757575;
}

.col_md_login > p {
  font-weight: 400;
margin-top: 15px;
width: 80%;
  color: #37474F;
}

.btn_login {  
background-color: #26C6DA;
  border: none;
  padding: 10px;
width: 200px;
border-radius:3px;
box-shadow: 1px 5px 20px -5px rgba(0,0,0,0.4);
  color: #fff;
margin-top: 10px;
cursor: pointer;
}

.col_md_sign_up {
  position: relative;
  float: left;
  width: 50%;  
}

.cont_ba_opcitiy > h2 {
  font-weight: 400;
  color: #fff;
}

.cont_ba_opcitiy > p {
  font-weight: 400;
margin-top: 15px;
  color: #fff;
}
/* ----------------------------------
background text  
------------------------------------
  */
.cont_ba_opcitiy {
  position: relative;
  background-color: rgba(120, 144, 156, 0.55);
  width: 80%;
  border-radius:3px ;
margin-top: 60px;
padding: 15px 0px;
}

.btn_sign_up {  
background-color: #ef5350;
  border: none;
  padding: 10px;
width: 200px;
border-radius:3px;
box-shadow: 1px 5px 20px -5px rgba(0,0,0,0.4);
  color: #fff;
margin-top: 10px;
cursor: pointer;
}
.cont_forms_active_sign_up {
z-index: 2;  
}

@-webkit-keyframes animar_fondo {
  from { -webkit-transform: scale(1) translate(0px);
-moz-transform: scale(1) translate(0px);
-ms-transform: scale(1) translate(0px);
-o-transform: scale(1) translate(0px);
transform: scale(1) translate(0px); }
  to { -webkit-transform: scale(1.5) translate(50px);
-moz-transform: scale(1.5) translate(50px);
-ms-transform: scale(1.5) translate(50px);
-o-transform: scale(1.5) translate(50px);
transform: scale(1.5) translate(50px); }
}
@-o-keyframes identifier {
  from { -webkit-transform: scale(1);
-moz-transform: scale(1);
-ms-transform: scale(1);
-o-transform: scale(1);
transform: scale(1); }
  to { -webkit-transform: scale(1.5);
-moz-transform: scale(1.5);
-ms-transform: scale(1.5);
-o-transform: scale(1.5);
transform: scale(1.5); }

}
@-moz-keyframes identifier {
  from { -webkit-transform: scale(1);
-moz-transform: scale(1);
-ms-transform: scale(1);
-o-transform: scale(1);
transform: scale(1); }
  to { -webkit-transform: scale(1.5);
-moz-transform: scale(1.5);
-ms-transform: scale(1.5);
-o-transform: scale(1.5);
transform: scale(1.5); }

}
@keyframes identifier {
  from { -webkit-transform: scale(1);
-moz-transform: scale(1);
-ms-transform: scale(1);
-o-transform: scale(1);
transform: scale(1); }
  to { -webkit-transform: scale(1.5);
-moz-transform: scale(1.5);
-ms-transform: scale(1.5);
-o-transform: scale(1.5);
transform: scale(1.5); }
}
.cont_form_login {
  position: absolute;
  opacity: 0;
display: none;
  width: 320px;
  -webkit-transition: all 0.5s;
-moz-transition: all 0.5s;
-ms-transition: all 0.5s;
-o-transition: all 0.5s;
transition: all 0.5s;
}

.cont_forms_active_login {
z-index: 2;  
}
.cont_forms_active_login >.cont_form_login {
}

.cont_form_sign_up {
  position: absolute;
  width: 320px;
float: left;
  opacity: 0;
display: none;
  -webkit-transition: all 0.5s;
-moz-transition: all 0.5s;
-ms-transition: all 0.5s;
-o-transition: all 0.5s;
transition: all 0.5s;
}

   
.cont_form_sign_up > input {
text-align: left;
  padding: 15px 5px;
margin-left: 10px;
margin-top: 20px;
  width: 260px;
border: none;
  color: #757575;
}

.cont_form_sign_up > h2 {
margin-top: 50px;  
font-weight: 400;
  color: #757575;
}

.cont_form_login > input {
  padding: 15px 5px;
margin-left: 10px;
margin-top: 20px;
  width: 260px;
border: none;
text-align: left;
  color: #757575;
}

.cont_form_login > h2 {
margin-top: 110px;  
font-weight: 400;
  color: #757575;
}
.cont_form_login > a,.cont_form_sign_up > a {
  color: #757575;
  position: relative;
  float: left;
  margin: 10px;
margin-left: 30px;
}

/* ------------------------------------ Click on login and Sign Up to changue and view the effect
---------------------------------------
*/

function cambiar_login() {
  document.querySelector('.cont_forms').className = "cont_forms cont_forms_active_login";  
document.querySelector('.cont_form_login').style.display = "block";
document.querySelector('.cont_form_sign_up').style.opacity = "0";  

setTimeout(function(){ document.querySelector('.cont_form_login').style.opacity = "1"; },400);  
   
setTimeout(function(){  
document.querySelector('.cont_form_sign_up').style.display = "none";
},200);  
  }

function cambiar_sign_up(at) {
  document.querySelector('.cont_forms').className = "cont_forms cont_forms_active_sign_up";
  document.querySelector('.cont_form_sign_up').style.display = "block";
document.querySelector('.cont_form_login').style.opacity = "0";
   
setTimeout(function(){ document.querySelector('.cont_form_sign_up').style.opacity = "1";
},100);  

setTimeout(function(){ document.querySelector('.cont_form_login').style.display = "none";
},400);  

}  

function ocultar_login_sign_up() {

document.querySelector('.cont_forms').className = "cont_forms";  
document.querySelector('.cont_form_sign_up').style.opacity = "0";  
document.querySelector('.cont_form_login').style.opacity = "0";  

setTimeout(function(){
document.querySelector('.cont_form_sign_up').style.display = "none";
document.querySelector('.cont_form_login').style.display = "none";
},500);  
   
  }