<form action="#!" id="main">
  <h2>Login to your account</h2>
  <div class="input-parent">
    <label for="username">Username or Email</label>
    <input type="text" id="username" />
  </div>
  <div class="input-parent">
    <label for="password">Password</label>
    <input type="password" id="password" />
  </div>
  <button type="submit">Login</button>
</form>

*,
*:before,
*:after {
  margin: 0;
  padding: 0;
  font-family: inherit;
  box-sizing: border-box;
}
#main {
  width: max-content;
  margin: 40px auto;
  font-family: "Segoe UI", sans-serif;
  padding: 25px 28px;
  background: #151414;
  border-radius: 4px;
  border: 1px solid #302d2d;
  animation: popup 0.4s cubic-bezier(0.68, -0.55, 0.27, 1.55);
}
@keyframes popup {
  0% {
    transform: scale(0.2);
    opacity: 0;
  }
  100% {
    transform: scale(1);
    opacity: 1;
  }
}
h2 {
  text-align: center;
  font-size: 28px;
  margin-bottom: 20px;
  font-weight: 400;
  color: #e7e7e7;
}
.input-parent {
  display: block;
  margin-bottom: 20px;
}
label {
  display: block;
  font-size: 16px;
  margin-bottom: 8px;
  color: #a4a4a4;
}
.input-parent input {
  padding: 10px 8px;
  width: 100%;
  font-size: 16px;
  background: #323131;
  border: none;
  color: #c7c7c7;
  border-radius: 4px;
  outline: none;
  transition: all 0.2s ease;
}
.input-parent input:hover {
  background: #404040;
}
.input-parent input:focus {
  box-shadow: 0px 0px 0px 1px #0087ff;
}
button {
  padding: 10px 18px;
  font-size: 15px;
  background: #1a3969;
  width: 100%;
  border: none;
  border-radius: 4px;
  color: #f4f4f4;
  transition: all 0.2s ease;
}
button:hover {
  opacity: 0.9;
}
button:focus {
  box-shadow: 0px 0px 0px 3px black;
}
body {
  background: #1c1b1b;
}