// Form
.form
  .form-toggle
  .form-panel.one
    .form-header
      h1 Account Login
    .form-content
      form
        .form-group
          label(for='username') Username
          input(type='text'
                id='username'
                name='username'
                required)
        .form-group
          label(for='password') Password
          input(type='password'
                id='password'
                name='password'
                required)
        .form-group
          label.form-remember
            input(type='checkbox')
            | Remember Me
          a.form-recovery(href='#') Forgot Password?
        .form-group
          button(type='submit') Log In
  .form-panel.two
    .form-header
      h1 Register Account
    .form-content
      form
        .form-group
          label(for='username') Username
          input(type='text'
                id='username'
                name='username'
                required)
        .form-group
          label(for='password') Password
          input(type='password'
                id='password'
                name='password'
                required)
        .form-group
          label(for='cpassword') Confirm Password
          input(type='password'
                id='cpassword'
                name='cpassword'
                required)
        .form-group
          label(for='email') Email Address
          input(type='email'
                id='email'
                name='email'
                required)
        .form-group
          button(type='submit') Register
.pen-footer
  a(href='https://www.behance.net/gallery/30478397/Login-Form-UI-Library'
    target='_blank')
    i.material-icons arrow_backward
    | View on Behance
  a(href='https://github.com/andyhqtran/UI-Library/tree/master/Login%20Form'
    target='_blank')
    | View on Github
    i.material-icons arrow_forward
View Compiled
// Font Family
$body-font: "Roboto";

// Font Weights
$thin: 100;
$light: 300;
$regular: 400;
$semibold: 500;
$bold: 700;
$ultra: 800;

// Base Font
$base-font-family: $body-font, sans-serif;
$base-font-size: 14px;
$base-font-weight: $regular;
$base-line-height: 1.6em;

// Colors
$black: #000000;
$dark-gray: rgba($black, 0.8);
$gray: rgba($black, 0.6);
$light-gray: rgba($black, 0.4);
$lighter-gray: rgba($black, 0.2);
$white: #FFFFFF;
$accent: #4285F4;

// Form Settings
$max-width: 600px;
$max-height: 400px;
$gutters: 24px;

html {
  width: 100%;
  height: 100%;
}

body {
  background: linear-gradient(45deg,  rgba(66, 183, 245,0.8) 0%,rgba(66, 245, 189,0.4) 100%);
  color: $gray;
  font-family: $base-font-family;
  font-size: $base-font-size;
  line-height: $base-line-height;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.overlay {
  position: absolute;
  top: 0;
  left: 0;
  display: none;
  background: rgba($black, 0.8);
  width: 100%;
  height: 100%;
}

.form {
  z-index: 15;
  position: relative;
  background: $white;
  width: $max-width;
  border-radius: 4px;
  box-shadow: 0 0 30px rgba($black, .1);
  box-sizing: border-box;
  margin: 100px auto 10px;
  overflow: hidden;

  // Toggle
  &-toggle {
    z-index: 10;
    position: absolute;
    top: 60px;
    right: 60px;
    background: $white;
    width: 60px;
    height: 60px;
    border-radius: 100%;
    transform-origin: center;
    transform: translate(0, -25%) scale(0);
    opacity: 0;
    cursor: pointer;
    transition: all 0.3s ease;

    &:before,
    &:after {
      content: '';
      display: block;
      position: absolute;
      top: 50%;
      left: 50%;
      width: 30px;
      height: 4px;
      background: $accent;
      transform: translate(-50%, -50%);
    }

    &:before {
      transform: translate(-50%, -50%) rotate(45deg);
    }

    &:after {
      transform: translate(-50%, -50%) rotate(-45deg);
    }

    &.visible {
      transform: translate(0, -25%) scale(1);
      opacity: 1;
    }
  }

  &-group {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    margin: 0 0 20px;

    &:last-child {
      margin: 0;
    }

    label {
      display: block;
      margin: 0 0 10px;
      color: $gray;
      font-size: 12px;
      font-weight: $semibold;
      line-height: 1;
      text-transform: uppercase;
      letter-spacing: .2em;

      .two & {
        color: $white;
      }
    }

    input {
      outline: none;
      display: block;
      background: rgba($black, 0.1);
      width: 100%;
      border: 0;
      border-radius: 4px;
      box-sizing: border-box;
      padding: 12px 20px;
      color: $gray;
      font-family: inherit;
      font-size: inherit;
      font-weight: $semibold;
      line-height: inherit;
      transition: 0.3s ease;

      &:focus {
        color: $dark-gray;
      }

      .two & {
        color: $white;

        &:focus {
          color: $white;
        }
      }
    }

    button {
      outline: none;
      background: $accent;
      width: 100%;
      border: 0;
      border-radius: 4px;
      padding: 12px 20px;
      color: $white;
      font-family: inherit;
      font-size: inherit;
      font-weight: $semibold;
      line-height: inherit;
      text-transform: uppercase;
      cursor: pointer;

      .two & {
        background: $white;
        color: $accent;
      }
    }

    .form-remember {
      font-size: 12px;
      font-weight: $regular;
      letter-spacing: 0;
      text-transform: none;

      input[type='checkbox'] {
        display: inline-block;
        width: auto;
        margin: 0 10px 0 0;
      }
    }

    .form-recovery {
      color: $accent;
      font-size: 12px;
      text-decoration: none;
    }
  }

  // Panel
  &-panel {
    padding: 60px calc(5% + 60px) 60px 60px;
    box-sizing: border-box;

    // Panel One
    &.one {
      &:before {
        @extend .overlay;

        content: '';
        display: block;
        opacity: 0;
        visibility: hidden;
        transition: 0.3s ease;
      }

      &.hidden {
        &:before {
          display: block;
          opacity: 1;
          visibility: visible;
        }
      }
    }

    // Panel Two
    &.two {
      z-index: 5;
      position: absolute;
      top: 0;
      left: 95%;
      background: $accent;
      width: 100%;
      min-height: 100%;
      padding: 60px calc(10% + 60px) 60px 60px;
      transition: 0.3s ease;
      cursor: pointer;

      &:before,
      &:after {
        content: '';
        display: block;
        position: absolute;
        top: 60px;
        left: 1.5%;
        background: rgba($white, 0.2);
        height: 30px;
        width: 2px;
        transition: 0.3s ease;
      }

      &:after {
        left: 3%;
      }

      &:hover {
        left: 93%;
        box-shadow: 0 0 10px rgba($black, 0.2);

        &:before,
        &:after {
          opacity: 0;
        }
      }

      &.active {
        left: 10%;
        box-shadow: 0 0 10px rgba($black, 0.2);
        cursor: default;

        &:before,
        &:after {
          opacity: 0;
        }
      }
    }
  }

  // Header
  &-header {
    margin: 0 0 40px;

    h1 {
      padding: 4px 0;
      color: $accent;
      font-size: 24px;
      font-weight: $bold;
      text-transform: uppercase;

      .two & {
        position: relative;
        z-index: 40;
        color: $white;
      }
    }
  }

  // Content
  &-content {}

  &-footer {}
}

// Pen Footer
.pen-footer {
  display: flex;
  flex-direction: row;
  justify-content: space-between;
  width: $max-width;
  margin: 20px auto 100px;

  a {
    color: $white;
    font-size: 12px;
    text-decoration: none;
    text-shadow: 1px 2px 0 rgba($black, .1);
    
    .material-icons {
      width: 12px;
      margin: 0 5px;
      vertical-align: middle;
      font-size: 12px;
    }
  }
}

.cp-fab {
  background: $white !important;
  color: $accent !important;
}
$(document).ready(function() {
  var panelOne = $('.form-panel.two').height(),
    panelTwo = $('.form-panel.two')[0].scrollHeight;

  $('.form-panel.two').not('.form-panel.two.active').on('click', function(e) {
    e.preventDefault();

    $('.form-toggle').addClass('visible');
    $('.form-panel.one').addClass('hidden');
    $('.form-panel.two').addClass('active');
    $('.form').animate({
      'height': panelTwo
    }, 200);
  });

  $('.form-toggle').on('click', function(e) {
    e.preventDefault();
    $(this).removeClass('visible');
    $('.form-panel.one').removeClass('hidden');
    $('.form-panel.two').removeClass('active');
    $('.form').animate({
      'height': panelOne
    }, 200);
  });
});

External CSS

  1. https://fonts.googleapis.com/css?family=Roboto:100,300,400,500,700,900|Material+Icons

External JavaScript

  1. //cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.min.js
  2. https://codepen.io/andytran/pen/vLmRVp.js