style.css

@import url("https://fonts.googleapis.com/css2?family=Open+Sans&display=swap");

* {
  padding: 0;
  margin: 0;
  box-sizing: border-box;
}

body {
  background-color: darkslateblue;
  font-family: "Open Sans", sans-serif;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}
.container {
  background-color: #fff;
  width: 400px;
  border-radius: 5px;
  overflow: hidden;
}
.header {
  background-color: #f7f7f7;
}
.header h2 {
  padding: 20px;
  text-align: center;
}
.form {
  padding: 20px 30px;
}
.form-control {
  margin-bottom: 10px;
  padding-bottom: 20px;
  position: relative;
}
.form-control label {
  display: block;
  margin-bottom: 5px;
}
.form-control input {
  display: block;
  width: 100%;
  padding: 10px;
  border-radius: 5px;
  outline: none;
  border: 2px solid #f0f0f0;
}
.form-control i {
  position: absolute;
  right: 10px;
  top: 40px;
  visibility: hidden;
}
.form-control small {
  position: absolute;
  left: 0;
  margin-top: 5px;
  visibility: hidden;
}
.form button {
  display: block;
  width: 100%;
  background-color: darkslateblue;
  color: white;
  padding: 10px;
  outline: none;
  border: none;
  border-radius: 5px;
  text-align: center;
}
.form-control.success input {
  border-color: rgb(48, 207, 48);
}
.form-control.success .fa-check-circle {
  visibility: visible;
  color: rgb(48, 207, 48);
}
.form-control.error input {
  border-color: red;
}
.form-control.error .fa-exclamation-circle {
  color: red;
  visibility: visible;
}
.form-control.error small {
  visibility: visible;
  color: red;
}