style.css

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

html {
    box-sizing: border-box;
}

body {
    margin: 0;
    min-height: 100vh;
    font-family: 'Creepster', cursive, sans-serif;
    letter-spacing: 2px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(#ff9e0d, #554e4e);
    color: rgb(250, 0, 0);
    text-shadow: 1px 2px 2px #ffee00;
    font-size: 20px;
}

.container {
    width: 480px;
    height: 630px;
    background: rgb(27, 26, 26);
    display: flex;
    flex-direction: column;
    align-items: center;
    border-radius: 10px;
    box-shadow: 0 5px 35px 10px rgba(255, 255, 255, 0.4);
}

/* Form */

form {
    width: 90%;
}

.form-group {
    height: 65px;
}

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

input {
    width: 100%;
    height: 35px;
    padding: 5px;
    border: 1px solid black;
    border-radius: 5px;
    outline: none;
    box-sizing: border-box;
    transition: all 0.3s;

}

input:valid {
    border: 2px solid rgb(73, 247, 82);
}

input:invalid {
    border: 2px solid red;
}

button {
    cursor: pointer;
    color: rgb(250, 0, 0);
    text-shadow: 0.5px 0.5px 2px #ffee00;
    border: none;
    border-radius: 5px;
    height: 50px;
    width: 100%;
    font-family: 'Creepster', cursive, sans-serif;
    font-size: 20px;
    letter-spacing: 2px;
    margin-top: 5px;
}

button:hover {
    filter: brightness(200%);
    background: rgb(26, 24, 24);
}

button:focus {
    outline: none;
}

.message-container {
    border-radius: 5px;
    outline: none;
    width: 90%;
    margin-top: 5px;
    display: flex;
    justify-content: center;
    color: rgb(250, 0, 0);
    text-shadow: 0.5px 0.5px 2px #ffee00;
}