<div class="sign-up">
  <div class="circle circle--red"></div>
  <div class="circle circle--yellow"></div>
  <div class="circle circle--green"></div>
  <div class="circle circle--purple"></div>
  <form class="sign-up__form" action="javascript:void(0)" method="post">
    <div class="sign-up__content">
      <h2 class="sign-up__title">Login</h2>
      <input class="sign-up__inp" type="email" placeholder="Email" required="required"/>
      <input class="sign-up__inp" type="password" placeholder="Password" required="required"/><a class="forgot__password">Forgot your password</a>
    </div>
    <div class="sign-up__buttons"><a class="btn btn--register" href="#register">Register</a>
      <button class="btn btn--signin" type="submit">Sign in</button>
    </div>
  </form>
</div>
@import url("https://fonts.googleapis.com/css?family=Montserrat:300,400,600&display=swap");
:root {
  --red: #ee596f;
  --yellow: #feb800;
  --green: #07a787;
  --purple: #c765d0;
  --gray: #787878;
  --gray-light: #eee;
  --gray-dark: #2e3c54;
  --font: "Montserrat", sans-serif;
}

a {
  text-decoration: none;
}

a,
button {
  cursor: pointer;
  outline: none;
}

.sign-up {
  font-family: var(--font);
  width: 100%;
  max-width: 800px;
  height: 600px;
  background-color: var(--gray-light);
  margin: 25px auto;
  position: relative;
  overflow: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
}
.sign-up__form {
  background-color: white;
  width: 80%;
  height: 70%;
  margin: 0 auto;
  position: relative;
  z-index: 10;
  border-radius: 8px;
  overflow: hidden;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
	box-shadow: 0 20px 20px 10px rgba(0,0,0,.15);
}
.sign-up__content {
  padding: 40px;
  display: flex;
  flex-flow: column nowrap;
}
.sign-up__title {
  color: var(--gray-dark);
  font-weight: 400;
  text-transform: uppercase;
  font-size: 25px;
  margin-bottom: 30px;
}
.sign-up__inp {
  outline: none;
  margin-bottom: 15px;
  padding: 20px 20px 20px 0;
  border: 0;
  border-bottom: 1px solid var(--gray-light);
  text-transform: uppercase;
  font-size: 16px;
  font-weight: 400;
  font-family: var(--font);
}
.sign-up__buttons {
  display: flex;
  justify-content: space-between;
}
.sign-up__buttons > * {
  width: 50%;
  padding: 20px 15px;
  border: 0;
  text-transform: uppercase;
  font-size: 16px;
}

.circle {
  position: absolute;
  border-radius: 50%;
}
.circle--red {
  width: 250px;
  height: 250px;
  background-color: var(--red);
  top: 25px;
  left: 25px;
  z-index: 1;
}
.circle--yellow {
  width: 100px;
  height: 100px;
  background-color: var(--yellow);
  top: 50px;
  left: 230px;
}
.circle--green {
  width: 300px;
  height: 300px;
  background-color: var(--green);
  bottom: 50px;
  left: 200px;
  z-index: 2;
}
.circle--purple {
  width: 300px;
  height: 300px;
  background-color: var(--purple);
  bottom: -50px;
  right: -50px;
  -webkit-transform: scale(1.8);
          transform: scale(1.8);
}

.forgot__password {
  text-align: center;
  text-transform: uppercase;
  color: var(--gray);
  display: inline-block;
  margin-top: 20px;
}

.btn--register {
  background-color: var(--gray-light);
  color: var(--gray);
}

.btn--signin {
  background-color: var(--gray-dark);
  color: white;
  text-align: right;
}

External CSS

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External JavaScript

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