index.css

@import url(https://fonts.googleapis.com/css?family=Poppins:100,100italic,200,200italic,300,300italic,regular,italic,500,500italic,600,600italic,700,700italic,800,800italic,900,900italic);

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

h1.logo {
  margin: auto 5px;
  font-size: 1.23em;
}

a {
  text-decoration: inherit;
  color: inherit;
  cursor: pointer;
}

a.active {
  color: blue;
}

li.link-item {
  padding: 5px 10px;
}

ul.link-list {
  list-style: none;
  display: flex;
  padding: 0;
}

header.nav-bar {
  display: flex;
  justify-content: space-between;
  border: solid 3px black;
}

section {
  display: block;
}

h1 {
  font-size: 3rem;
  margin-top: 0.75rem;
}

.nav-bar {
  display: flex;
  width: 100%;
  border: 4px solid black;
  justify-content: space-between;
  align-items: center;
  margin-top: 10px;
  margin-bottom: 10px;
  padding: 10px;
}

.nav-bar .nav-menu-div {
  display: flex;
  justify-content: center;
  column-gap: 20px;
  font-weight: 700;
}

.nav-bar li {
  list-style-type: none;
}

#first-list,
#second-list {
  border-right: 3px solid black;
  padding-right: 10px;
}

.menu-link:focus {
  color: rgb(67, 133, 246);
}

.container {
  gap: 2.25rem;

  /* background-color: yellow; */
  padding: 10px;
  width: 100%;
}

.container-h2 {
  padding: 20px;
}

.add-page,
.contact-me {
  display: none;
  flex-direction: column;
  row-gap: 10px;
  width: 100%;
  font-size: larger;
  align-items: center;
}

.contact-me h2 {
  padding-bottom: 20px;
}

.display-page {
  justify-content: center;
  align-items: center;
  width: 100%;
}

.book-list {
  list-style: none;
  width: 100%;
  padding: 10px;
  border: 4px solid black;

  /* position: relative; */
  max-height: 15rem;
  overflow-y: scroll;
}

.list {
  display: flex;
  flex-direction: row;
  align-items: center;
  gap: 7px;
  padding: 1rem;
}

.list:nth-child(odd) {
  background-color: rgba(128, 128, 128, 0.6);
}

footer {
  border: 5px solid #333;
  display: flex;
  width: 100%;
  justify-content: space-between;
  align-items: center;
  padding: 8px;
  margin-top: 360px;
  font-weight: bolder;
  font-size: larger;
}

.list h2,
.list button {
  font-size: 22px;
  font-weight: normal;
  margin: 0;
}

.list button {
  border: 3px solid black;
  margin-left: auto;
  padding: 0.25rem 0.6rem;
  box-shadow: 6px 6px 2px 0 black;
}

.list button:active {
  transform: translate(6px, 6px);
  box-shadow: 0 0 0 0 black;
}

.form-heading {
  font-size: 2.75rem;
  text-align: center;
}

#book-form {
  width: 20%;
}

.input {
  margin-bottom: 0.8rem;
  padding: 0.25rem 0.6rem;
  height: 2.6rem;
  width: 100%;
  border: 3px solid black;
}

.add-btn {
  /* width: 80px; */
  align-self: flex-end;
  height: max-content;
  float: right;
  font-weight: bold;
  padding: 0.4rem 1rem;
  border: 3px solid black;
  box-shadow: 4px 4px 2px 0 black;
}

.input::placeholder {
  color: black;
  font-weight: bold;
}

.input.add:active {
  transform: translate(6px, 6px);
  box-shadow: 0 0 0 0 black;
}

.time {
  text-align: right;
}