style.css

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

html {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: Sen, sans-serif;
  letter-spacing: 2px;
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: #c9ced3;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='40' height='40' viewBox='0 0 40 40'%3E%3Cg fill-rule='evenodd'%3E%3Cg fill='%23000000' fill-opacity='0.4'%3E%3Cpath d='M0 38.59l2.83-2.83 1.41 1.41L1.41 40H0v-1.41zM0 1.4l2.83 2.83 1.41-1.41L1.41 0H0v1.41zM38.59 40l-2.83-2.83 1.41-1.41L40 38.59V40h-1.41zM40 1.41l-2.83 2.83-1.41-1.41L38.59 0H40v1.41zM20 18.6l2.83-2.83 1.41 1.41L21.41 20l2.83 2.83-1.41 1.41L20 21.41l-2.83 2.83-1.41-1.41L18.59 20l-2.83-2.83 1.41-1.41L20 18.59z'/%3E%3C/g%3E%3C/g%3E%3C/svg%3E");
}

.container {
  width: 480px;
  height: 630px;
  background: white;
  display: flex;
  flex-direction: column;
  align-items: center;
  border-radius: 5px;
  box-shadow: 0 5px 15px 5px rgba(0, 0, 0, 0.1);
}

/* Form */
form {
  width: 90%;
}

.form-group {
  height: 65px;
}

label {
  position: relative;
  bottom: 3px;
}

input {
  width: 100%;
  height: 34px;
  padding: 5px;
  border: 1px solid black;
  border-radius: 2px;
  outline: none;
  box-sizing: border-box;
  transition: all 0.3s;
}

input:valid {
  border: 1px solid chartreuse;
}

input:invalid {
  border: 1px solid crimson;
}

button {
  cursor: pointer;
  color: white;
  background: black;
  border: none;
  border-radius: 2px;
  height: 50px;
  width: 100%;
  font-family: Sen, sans-serif;
  font-size: 20px;
  letter-spacing: 2px;
  margin-top: 5px;
}

button:hover {
  filter: brightness(200%);
  background: rgb(22, 22, 22);
}

button:focus {
  outline: none;
}

.message-container {
  border: 1px solid black;
  border-radius: 2px;
  width: 90%;
  margin-top: 20px;
  display: flex;
  justify-content: center;
  color: black;
}