:root {
  --custom-primary-color: #004987;
  --custom-primary-rgb: 0, 73, 135;
}

/* --- Logo Icon --- */
.logo {
  color: var(--custom-primary-color);
}

/* --- Category Buttons --- */
.category-button {
  width: 96px;
  height: 96px;
  border: 1px solid var(--bs-border-color-translucent);
  transition: all 0.2s ease-in-out;
  color: var(--custom-primary-color);
  background-color: #fff;
}

.category-button:hover:not(.active):not(:disabled) {
  transform: translateY(-4px);
  box-shadow: var(--bs-box-shadow-lg) !important;
  color: var(--custom-primary-color);
}

.category-button:active,
.category-button.active:active,
.category-button.active,
.category-button:focus,
.category-button.active:focus {
  background-color: var(--custom-primary-color);
  color: #fff;
  border-color: var(--custom-primary-color);
}

.category-button:focus:not(:focus-visible) {
  color: var(--custom-primary-color);
  background-color: #fff;
}

.category-button > .icon {
  font-size: 36px;
  width: 36px;
  height: 36px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

/* --- Letter Buttons --- */
.letter-button {
  width: 32px;
  height: 32px;
  font-weight: bold;
  padding: 0;
  border: 0;
  background-color: var(--bs-secondary-bg);
  color: var(--bs-secondary-color);
  transition: background-color 0.15s ease-in-out;
}
.letter-button:hover:not(:disabled) {
  background-color: var(--bs-secondary-bg-subtle);
}
.letter-button.active {
  background-color: var(--bs-primary);
  color: #fff;
}
.letter-button.relevant {
  background-color: var(--bs-info-bg-subtle);
  color: var(--bs-info-text-emphasis);
  font-weight: bold;
}
.letter-button.relevant:hover:not(:disabled) {
  background-color: var(--bs-info-bg-subtle);
  filter: brightness(0.95);
}
.letter-button:disabled {
  background-color: var(--bs-tertiary-bg);
  color: var(--bs-tertiary-color);
  cursor: not-allowed;
  opacity: 0.65;
}

/* --- Scroll to Top Button --- */
#scroll-to-top-button {
    position: fixed;
    bottom: 20px;
    right: 20px;
    z-index: 1050;
    width: 50px;
    height: 50px;
    font-size: 1.5rem;
    background-color: var(--custom-primary-color);
    border-color: var(--custom-primary-color);
}

#scroll-to-top-button:hover,
#scroll-to-top-button:focus {
    background-color: rgba(var(--custom-primary-rgb), 0.85);
    border-color: rgba(var(--custom-primary-rgb), 0.85);
}

/* --- Disabled State for Subcategory Cards --- */
.subcategory-card.disabled {
  opacity: 0.6;
  background-color: var(--bs-secondary-bg) !important;
}

.subcategory-card.disabled .card-body,
.subcategory-card.disabled .card-body * {
   cursor: not-allowed;
}

.subcategory-card.disabled a.btn {
  pointer-events: none;
  display: none;
}