.btn{
   width: 390px;
   height: 120px; 
   color: #fff; 
   background: linear-gradient(0deg, rgba(0, 172, 238, 1) 0%, rgba(2, 126, 251, 1) 100%);
   font-family: 'Lato', sans-serif;
   font-weight: 500;
   border-radius: 10px;
   box-shadow: inset 2px 2px 2px 0px rgba(255, 255, 255, .5),
   7px 7px 20px 0px rgba(0, 0, 0, .1),
   4px 4px 5px 0px rgba(0, 0, 0, .1);
   transition: all 0.3s ease;
   cursor: pointer;
   border: none;
   position: relative;
   line-height: 120px;
   padding: 0;
}
.btn span{
    position: relative;
    display: block;
    width: 100%;
    height: 100%;
    font-size: 48px;
}
.btn::before,.btn::after{
    position:absolute;
    content: '';
    top: 0;
    right: 0;
    background: rgba(2, 126, 251, 1); 
    transition: all 0.3s ease;
}
.btn::before{
    width: 0;
    height: 2px;
}
.btn::after{
    height: 0;
    width: 2px;
}
.btn span::before,
.btn span::after{
    position:absolute;
    content: '';
    bottom: 0;
    left: 0;
    background: rgba(2, 126, 251, 1);
    transition: all 0.3s ease;
}
.btn span::before{
    width: 0;
    height: 2px;
}
.btn span::after{
    height: 0;
    width: 2px;
}

.btn:hover{
    background: transparent;
    color: rgba(2, 126, 251, 1);
}

.btn:hover::before{
    width: 100%;
}
.btn:hover::after{
    height: 100%;
}
.btn span:hover::before{
    width: 100%;
}
.btn span:hover::after{
    height: 100%;
}