main.css

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}
  
html {
    scroll-behavior: smooth;
}

body {
    font-family: "Poppins", sans-serif;
    background: #ededed;
    color: yellowgreen;
    line-height: 1.5;
}

header {
    text-align: center;
    background-color: yellowgreen;
    color: #fff;
    padding: 1.5rem 0;
}

main {
    padding-bottom: 5rem;
}

.container {
    width: 90%;
    margin: 0 auto;
    max-width: 800px;
}

.center {
    display: flex;
    justify-content: center;
    align-items: center;
}

.card {
    background-color: #fff;
    padding: 2rem;
    margin-top: 2rem;
    border-radius: .8rem;
    box-shadow: 0 4px 8px rgba(154, 160, 185, .05), 0 8px 16px rgba(166, 173, 201, .2);
}

.text-center {
    text-align: center;
}

.form-group {
    display: flex;
    flex-direction: column;
    margin-bottom: 1.5rem;
}

label {
    font-weight: 700;
}

input[type="text"], input[type="number"], textarea {
    font-family: 'Poppins', sans-serif;
    border-radius: .5rem;
    padding: .5rem;
    font-size: 1.1rem;
}

button {
    font-family: 'Poppins', sans-serif;
    border-radius: .5rem;
    padding: .5rem 1.3rem;
    color: #fff;
    cursor: pointer;
    border: none;
    font-size: 1.1rem;
}

button:hover {
    scale: 1.02;
    box-shadow: 0 2px 4px rgba(154, 160, 185, .05), 0 8px 16px rgba(166, 173, 201, .2);
}

#bookFormSubmit {
    background-color: yellowgreen;
    width: 100%;
    margin-top: 1rem;
}

#bookFormSubmit span {
    font-weight: 700;
}

#searchBook {
    margin-top: 1rem;
}

#searchBookTitle {
    width: 50%;
    margin: 0 .5rem;
}

#searchSubmit {
    background-color: yellowgreen;
    width: 25%;
}

.bookItem {
    border: 1px solid #ededed;
    padding: 1.5rem;
    border-radius: .5rem;
    margin-top: 1rem;
    box-shadow: 0 2px 4px rgba(154, 160, 185, .05), 0 8px 16px rgba(166, 173, 201, .2);
    color: #444;
}

.bookItem p {
    margin: .25rem 0;
}

.bookItem .action {
    margin-top: 1rem;
}

.completeBook, .incompleteBook, .deleteBook, .editBook {
    margin: 0 .2rem;
    font-size: .8rem;
}

.completeBook, .incompleteBook {
    background-color: rgb(25, 135, 84);
}

.deleteBook {
    background-color: rgb(220, 53, 69);
}

.editBook {
    background-color: rgb(13, 110, 253);
}