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html {
 height: 100%;
}

body {
 margin: 0;
 padding: 0;
 font-family: sans-serif;
 background: linear-gradient(#141e30, #243b55);
}

.login-box {
 position: absolute;
 top: 50%;
 left: 50%;
 width: 400px;
 padding: 40px;
 transform: translate(-50%, -50%);
 background: rgba(0, 0, 0, .5);
 box-sizing: border-box;
 box-shadow: 0 15px 25px rgba(0, 0, 0, .6);
 border-radius: 10px;
}

.login-box h2 {
 margin: 0 0 30px;
 padding: 0;
 color: #fff;
 text-align: center;
}

.login-box .user-box {
 position: relative;
}

.login-box .user-box input {
 width: 100%;
 padding: 10px 0;
 font-size: 16px;
 color: #fff;
 margin-bottom: 30px;
 border: none;
 border-bottom: 1px solid #fff;
 outline: none;
 background: transparent;
}

.login-box .user-box label {
 position: absolute;
 top: 0;
 left: 0;
 padding: 10px 0;
 font-size: 16px;
 color: #fff;
 pointer-events: none;
 transition: .5s;
}

.login-box .user-box input:focus ~ label, .login-box .user-box input:valid ~ label {
 top: -20px;
 left: 0;
 color: #03e9f4;
 font-size: 12px;
}

.login-box form a {
 position: relative;
 display: inline-block;
 padding: 10px 20px;
 color: #03e9f4;
 font-size: 16px;
 text-decoration: none;
 text-transform: uppercase;
 overflow: hidden;
 transition: .5s;
 margin-top: 40px;
 letter-spacing: 4px
}

.login-box a:hover {
 background: #03e9f4;
 color: #fff;
 border-radius: 5px;
 box-shadow: 0 0 5px #03e9f4, 0 0 25px #03e9f4, 0 0 50px #03e9f4, 0 0 100px #03e9f4;
}

.login-box a span {
 position: absolute;
 display: block;
}

.login-box a span:nth-child(1) {
 top: 0;
 left: -100%;
 width: 100%;
 height: 2px;
 background: linear-gradient(90deg, transparent, #03e9f4);
 animation: btn-anim1 1s linear infinite;
}

@keyframes btn-anim1 {
 0% {
  left: -100%;
 }

 50%, 100% {
  left: 100%;
 }

}

.login-box a span:nth-child(2) {
 top: -100%;
 right: 0;
 width: 2px;
 height: 100%;
 background: linear-gradient(180deg, transparent, #03e9f4);
 animation: btn-anim2 1s linear infinite;
 animation-delay: .25s
}

@keyframes btn-anim2 {
 0% {
  top: -100%;
 }

 50%, 100% {
  top: 100%;
 }

}

.login-box a span:nth-child(3) {
 bottom: 0;
 right: -100%;
 width: 100%;
 height: 2px;
 background: linear-gradient(270deg, transparent, #03e9f4);
 animation: btn-anim3 1s linear infinite;
 animation-delay: .5s
}

@keyframes btn-anim3 {
 0% {
  right: -100%;
 }

 50%, 100% {
  right: 100%;
 }

}

.login-box a span:nth-child(4) {
 bottom: -100%;
 left: 0;
 width: 2px;
 height: 100%;
 background: linear-gradient(360deg, transparent, #03e9f4);
 animation: btn-anim4 1s linear infinite;
 animation-delay: .75s
}

@keyframes btn-anim4 {
 0% {
  bottom: -100%;
 }

 50%, 100% {
  bottom: 100%;
 }

}