body {
  font-family: 'Roboto', sans-serif;
  margin: 0;
  padding: 0;
  color: #333;
  background: #f9f9f9 url('/img/Nền.svg') center/cover no-repeat fixed;
}

header {
  background: #FFF9E5;
  color: #000;
  padding: 5px;
  text-align: center;
  font-size: 13px;
}

.container {
  font-size: 4px;
  padding: 20px;
  max-width: 1100px;
  margin: auto;
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 36px;
}

.psi-book-box {
  background: #fff;
  border-radius: 10px;
  box-shadow: 0 4px 10px rgba(0,0,0,0.06);
  padding: 10px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  height: 100%;
  transition: transform 0.3s, box-shadow 0.3s;
}

.psi-book-box:hover {
  transform: translateY(-4px);
  box-shadow: 0 6px 18px rgba(0,0,0,0.1);
}

.psi-book-content {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 14px;
}

.psi-book-text {
  flex: 2;
  padding-left: 10px;
}

.psi-book-title {
  font-size: 16px;
  font-weight: bold;
  margin-bottom: 6px;
  line-height: 1.4;
}

.psi-tag {
  display: inline-block;
  background: #e0f2ff;
  color: #005baa;
  font-size: 10px;
  font-weight: 500;
  padding: 4px 10px;
  border-radius: 999px;
  margin: 6px 0;
}

.psi-book-description {
  font-size: 10px;
  line-height: 1.4;
  color: #444;
}

.psi-highlight {
  color: red;
  font-weight: bold;
}

.psi-book-links {
  list-style: none;
  padding: 0;
  margin: 8px 0;
}

.psi-book-links li {
  font-size: 14px;
  line-height: 1.6;
}

.psi-book-links a {
  color: #005baa;
  text-decoration: none;
  transition: color 0.3s;
}

.psi-book-links a:hover {
  text-decoration: underline;
  color: #003d7a;
}

.psi-buy-btn {
  margin-top: 10px;
  background: #005baa;
  color: #fff;
  padding: 10px 20px;
  font-weight: bold;
  text-decoration: none;
  border-radius: 6px;
  font-size: 13px;
  display: inline-block;
  transition: background 0.3s;
}

.psi-buy-btn:hover {
  background: #f57f17;
}

.psi-book-image {
  flex: 1;
  display: flex;
  justify-content: center;
  align-items: flex-start;
  padding-top: 60px;
}

.psi-book-image img {
  max-width: 150px;
  width: 100px;
  height: auto;
  border-radius: 6px;
  margin-top: 0 !important;
}

/* Load More button */
.load-more-container {
  display: flex;
  justify-content: center;
  align-items: center;
  margin: 20px auto;
  width: 100%;
  position: relative;
}

.spinner {
  width: 40px;
  height: 40px;
  border: 6px solid #f3f3f3;
  border-top: 6px solid #3498db;
  border-radius: 50%;
  animation: spin 1s linear infinite;
  position: absolute;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

#loadMoreBtn {
  padding: 12px 24px;
  background: #005baa;
  color: white;
  font-size: 16px;
  font-weight: bold;
  border: none;
  border-radius: 6px;
  cursor: pointer;
  transition: background 0.3s;
}

#loadMoreBtn:hover {
  background: #003d7a;
}

#loadMoreBtn:disabled {
  background: #ccc;
  cursor: not-allowed;
}

#loadMoreBtn:disabled:hover {
  background: #ccc;
}

#loadMoreBtn:disabled .spinner {
  display: none;
}

/* Popup */
.popup-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.5);
  justify-content: center;
  align-items: center;
  z-index: 9999;
}

.popup-overlay.show {
  display: flex !important;
}

.popup-form {
  background: #fffef5;
  padding: 20px;
  border-radius: 10px;
  width: 90%;
  max-width: 500px;
  box-shadow: 0 6px 20px rgba(0,0,0,0.2);
  font-size: 14px;
  position: relative;
}

.popup-form h3 {
  text-align: center;
  font-size: 16px;
  margin-bottom: 16px;
}

.popup-form label {
  display: block;
  margin-bottom: 10px;
}

.popup-form input {
  width: 96%;
  padding: 8px;
  border: 1px solid #4442b2;
  border-radius: 6px;
  margin-top: 2px;
}

.popup-form button {
  width: 100%;
  margin-top: 12px;
  padding: 10px;
  font-size: 15px;
  font-weight: bold;
  border: none;
  border-radius: 8px;
  cursor: pointer;
}

.popup-form button[type="submit"] {
  background: #005baa;
  color: white;
}

.popup-form .close-btn {
  position: absolute;
  top: 10px;
  right: 16px;
  font-size: 22px;
  font-weight: bold;
  color: #333;
  cursor: pointer;
}

/* Responsive */
@media (max-width: 576px) {
  .container {
    grid-template-columns: 1fr;
  }

  .psi-book-content {
    flex-direction: column;
    align-items: flex-start;
    gap: 0;
    text-align: left;
  }

  .psi-book-text {
    width: 100%;
  }

  .psi-tag {
    margin-bottom: 4px !important;
  }

  .psi-book-image {
    margin: 0 !important;
    padding: 0 !important;
    text-align: center;
  }

  .psi-book-image img {
    max-width: 100px;
    margin: 4px auto !important;
  }

  .psi-book-description {
    margin-top: 4px !important;
    padding-top: 0 !important;
  }

  .psi-book-text > * {
    margin-top: 0 !important;
  }
}