/*- GENERAL STYLES -*/
@import url("https://fonts.googleapis.com/css2?family=Inter:wght@400;600;700&display=swap");

:root {
  --bg-color: #0f172a;
  --primary-color: #8a2be2;
  --secondary-color: #4a00e0;
  --accent-color: #3b82f6;
  --text-color: #e2e8f0;
  --card-bg-color: rgba(255, 255, 255, 0.05);
  --card-border-color: rgba(255, 255, 255, 0.1);
  --shadow-color: rgba(0, 0, 0, 0.2);
  --font-family: "Inter", sans-serif;
}

body {
  background-color: var(--bg-color);
  color: var(--text-color);
  font-family: var(--font-family);
  margin: 0;
  padding: 0;
  overflow-x: hidden;
}

.container-wrapper {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 2rem;
}

/*- HEADER -*/
.main-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 2rem 0;
}

.logo {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.logo h1 {
  font-size: 1.75rem;
  font-weight: 700;
}

.main-nav a {
  color: var(--text-color);
  text-decoration: none;
  font-size: 1rem;
  padding: 0.5rem 1rem;
  border-radius: 9999px;
  transition: background-color 0.3s ease;
}

.main-nav a:hover {
  background-color: var(--card-bg-color);
}

/*- HERO SECTION -*/
.hero-section {
  text-align: center;
  padding: 4rem 0;
}

.hero-section h2 {
  font-size: 3rem;
  font-weight: 700;
  background: linear-gradient(
    to right,
    var(--primary-color),
    var(--accent-color)
  );
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  margin-bottom: 1rem;
}

.hero-section p {
  font-size: 1.25rem;
  color: var(--text-color);
  margin-bottom: 2rem;
}

.search-container {
  position: relative;
  max-width: 500px;
  margin: 0 auto;
}

.search-icon {
  position: absolute;
  top: 50%;
  left: 1rem;
  transform: translateY(-50%);
  color: var(--text-color);
}

#searchBooks {
  width: 100%;
  padding: 1rem 1rem 1rem 3rem;
  border: 1px solid var(--card-border-color);
  border-radius: 9999px;
  background-color: var(--card-bg-color);
  font-size: 1rem;
  transition: all 0.3s ease;
}

#searchBooks:focus {
  outline: none;
  border-color: var(--accent-color);
  box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.5);
}

#searchBooks::placeholder {
  color: var(--text-color);
}

/*- BENTO GRID -*/
.bento-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 1.5rem;
  padding: 2rem 0;
}

.book-btn {
  background-color: var(--card-bg-color);
  border: 1px solid var(--card-border-color);
  border-radius: 1rem;
  padding: 1.5rem;
  text-align: left;
  color: var(--text-color);
  transition: all 0.3s ease;
  backdrop-filter: blur(10px);
  position: relative;
  overflow: hidden;
}

.book-btn:hover {
  transform: translateY(-5px);
  border-color: var(--primary-color);
}

.book-btn.category {
  grid-column: span 2;
  background: linear-gradient(
    to right,
    var(--primary-color),
    var(--secondary-color)
  );
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
}

.book-btn h3 {
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.book-btn p {
  font-size: 1rem;
  color: var(--text-color);
}

/*- TOPIC VIEW -*/
.topic-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 2rem 0;
  border-bottom: 1px solid var(--card-border-color);
}

#bookTitle {
  font-size: 2rem;
  font-weight: 700;
}

.topic-controls input,
.topic-controls button {
  padding: 0.5rem 1rem;
  border-radius: 9999px;
  border: 1px solid var(--card-border-color);
  background-color: var(--card-bg-color);
  color: var(--text-color);
  font-size: 1rem;
  transition: all 0.3s ease;
}

.topic-controls input:focus {
  outline: none;
  border-color: var(--accent-color);
}

.topic-controls button:hover {
  background-color: var(--accent-color);
}

#backToBooksBtn {
    background-color: var(--primary-color);
    color: white;
    padding: 0.5rem 1rem;
    border-radius: 0.5rem;
    border: none;
    cursor: pointer;
    transition: background-color 0.3s ease;
}

#backToBooksBtn:hover {
    background-color: var(--secondary-color);
}

#categoryBackBtn {
    background-color: var(--primary-color);
    color: white;
    padding: 0.5rem 1rem;
    border-radius: 0.5rem;
    border: none;
    cursor: pointer;
    transition: background-color 0.3s ease;
}

#categoryBackBtn:hover {
    background-color: var(--secondary-color);
}

.provider-selector {
  display: flex;
  justify-content: center;
  gap: 1rem;
  margin: 2rem 0;
}

.provider-btn {
  padding: 0.5rem 1.5rem;
  border-radius: 9999px;
  border: 1px solid var(--card-border-color);
  background-color: transparent;
  color: var(--text-color);
  font-size: 1rem;
  transition: all 0.3s ease;
}

.provider-btn.active {
  background-color: var(--primary-color);
  border-color: var(--primary-color);
}

/*- TOPIC GRID -*/
.topic-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 1.5rem;
  padding: 2rem 0;
}

.topic-card {
  background-color: var(--card-bg-color);
  border: 1px solid var(--card-border-color);
  border-radius: 1rem;
  padding: 1.5rem;
  backdrop-filter: blur(10px);
  transition: all 0.3s ease;
}

.topic-card:hover {
  border-color: var(--accent-color);
}

.topic-title {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
}

.topic-note {
  font-size: 0.875rem;
  color: #94a3b8;
  margin-bottom: 1rem;
}

.topic-card-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1rem;
}

.math {
  background-color: rgba(138, 43, 226, 0.2);
  color: #c471f5;
  padding: 0.25rem 0.5rem;
  border-radius: 0.25rem;
  font-size: 0.875rem;
  margin-bottom: 1rem;
  display: inline-block;
}

.category-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 2rem;
}

#breadcrumbs {
  text-align: right;
}

.topic-actions {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  border: 1px solid var(--card-border-color);
  padding: 0.5rem;
  border-radius: 0.5rem;
}

.topic-buttons {
  display: flex;
  gap: 0.5rem;
  margin-top: 1rem;
}

.topic-buttons button.search-btn,
.topic-buttons button.study-btn,
.topic-buttons button.copy-btn {
  flex-grow: 1;
  padding: 0.5rem;
  border-radius: 0.5rem;
  border: 1px solid var(--card-border-color);
  background-color: var(--card-bg-color);
  color: var(--text-color);
  cursor: pointer;
  transition: background-color 0.3s ease;
}

.topic-buttons button:hover {
  background-color: var(--accent-color);
}

/*- FOOTER -*/
.main-footer {
  text-align: center;
  padding: 2rem 0;
  border-top: 1px solid var(--card-border-color);
  margin-top: 2rem;
}

/*- UTILITIES -*/
.hidden {
  display: none;
}

.loader {
  border: 4px solid var(--card-bg-color);
  border-top: 4px solid var(--accent-color);
  border-radius: 50%;
  width: 40px;
  height: 40px;
  animation: spin 1s linear infinite;
  position: fixed;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  z-index: 9999;
}

@keyframes spin {
  0% {
    transform: rotate(0deg);
  }
  100% {
    transform: rotate(360deg);
  }
}

#scrollTopBtn {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  width: 3rem;
  height: 3rem;
  background-color: var(--primary-color);
  color: white;
  border: none;
  border-radius: 50%;
  font-size: 1.25rem;
  cursor: pointer;
  transition: all 0.3s ease;
  display: none; /* Hidden by default */
}

#scrollTopBtn:hover {
  background-color: var(--secondary-color);
  transform: scale(1.1);
}

/*- RESPONSIVE STYLES -*/
@media (max-width: 768px) {
  .container-wrapper {
    padding: 0 1rem;
  }

  .main-header {
    flex-direction: column;
    gap: 1rem;
  }

  .hero-section h2 {
    font-size: 2rem;
  }

  .hero-section p {
    font-size: 1rem;
  }

  .bento-grid {
    grid-template-columns: 1fr;
  }

  .book-btn.category {
    grid-column: span 1;
  }

  .topic-header {
    flex-direction: column;
    gap: 1rem;
  }

  .topic-controls {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    width: 100%;
  }

  .provider-selector {
    flex-direction: column;
    gap: 0.5rem;
  }
}