* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: Impact, Haettenschweiler, 'Arial Narrow Bold', sans-serif;
}

body {
  background: lightblue;
}

.header-container {
  border-bottom: 2px solid black;
  padding: 20px 10px 20px 10px;
  background: whitesmoke;
  box-shadow: 2px 2px 2px gray;
}

.btn-container {
  padding: 2rem;
}

.add-book-btn {
  padding: 10px;
  margin: 0 auto;
  display: block;
  cursor: pointer;
  background: blue;
  color: aliceblue;
  border: 2px solid black;
  outline: none;
  border-radius: 6px;
  font-size: 1.2rem;
}

.book-shelf {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 500px));
  padding: 10px;
  gap: 1rem;
  justify-content: center;
}

.book {
  background: white;
  border-radius: 1rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
  padding: 20px;
}

.delete-btn {
  background: red;
  outline: none;
  border: none;
  color: white;
  padding: 10px;
  border-radius: 5px;
  font-size: 1.2rem;
  width: 90%;
}

.read-stat {
  background: blue;
  outline: none;
  border: none;
  color: white;
  padding: 10px;
  border-radius: 5px;
  font-size: 1.2rem;
  width: 90%;
}

.read-stat-active {
  background: green;
  outline: none;
  border: none;
  color: white;
  padding: 10px;
  border-radius: 5px;
}

.modal {
   /* Hidden by default */
  display: none;
  position: fixed; /* Stay in place */
  z-index: 1; /* Sit on top */
  left: 0;
  top: 0;
  width: 100%; /* Full width */
  height: 100%; /* Full height */
  background-color: rgba(0,0,0,0.5); /* Black w/ opacity */
  justify-content: center;
  align-items: center;
}

.modal-form {
  background-color: white;
  display: flex;
  flex-direction: column;
  gap: 1rem;
  width: 95vw;
  padding: 1rem;
  border-radius: 1rem;
}

.form-header {
  border-bottom: 2px solid black;
  margin-bottom: 1rem;
  display: flex;
  justify-content: space-between;
}

form input {
  width: 100%;
  height: 2rem;
  border-radius: 0.3rem;
  background: #d1d5db;
  border: 2px solid #cbd5e1;
  outline: none;
  font-size: 1rem;
}

input:required:focus:valid {
  border: 2px solid green;
}

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

.submit-btn {
  margin-top: 1.01rem;
  outline: none;
  border: none;
  color: white;
  padding: 10px;
  border-radius: 5px;
  font-size: 1.2rem;
  width: 90%;
  background: blue;
  margin: 0 auto;
  cursor: pointer;
}

.exit-btn {
  cursor: pointer;
}

@media screen and (min-width: 900px) {
  .book h4 {
    font-size: 1.5rem;
  }

  .modal-form {
    width: 500px;
  }
}