/* ============================================
   PERIODIC TABLE MEMORY MASTER - Main Styles
   ============================================ */

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

body {
  font-family:
    -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen", "Ubuntu", "Cantarell",
    "Fira Sans", "Droid Sans", "Helvetica Neue", sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  min-height: 100vh;
  color: #333;
}

/* ============================================
   App Container & Layout
   ============================================ */

.app-container {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

.app-header {
  background: rgba(255, 255, 255, 0.95);
  padding: 30px 20px;
  text-align: center;
  border-bottom: 1px solid rgba(0, 0, 0, 0.08);
}

.app-header .header-icon {
  font-size: 48px;
  color: var(--color-primary, #1cb0f6);
  margin-bottom: 10px;
}

.app-header h1 {
  font-size: 32px;
  color: var(--color-primary, #1cb0f6);
  margin-bottom: 10px;
  font-weight: 700;
}

.app-header p {
  font-size: 16px;
  color: var(--color-text-muted, #6b7280);
}

.app-main {
  flex: 1;
  padding: 30px 20px;
  max-width: 1200px;
  margin: 0 auto;
  width: 100%;
}

.app-footer {
  background: rgba(0, 0, 0, 0.1);
  color: white;
  text-align: center;
  padding: 20px;
  margin-top: 30px;
}

/* ============================================
   Screens
   ============================================ */

.screen {
  display: none;
  animation: fadeIn 0.3s ease-in;
}

.screen.active {
  display: block;
}

@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.screen-content {
  background: white;
  border-radius: 12px;
  padding: 40px;
  border: 1px solid rgba(0, 0, 0, 0.08);
}

.screen-content h2 {
  font-size: 28px;
  color: #333;
  margin-bottom: 10px;
}

.subtitle {
  font-size: 16px;
  color: #999;
  margin-bottom: 30px;
}

/* ============================================
   Chunk Selection Grid
   ============================================ */

.chunks-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 20px;
  margin: 30px 0;
}

.chunk-card {
  background: white;
  border: 2px solid #eee;
  border-radius: 8px;
  padding: 20px;
  cursor: pointer;
  transition: all 0.3s ease;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.chunk-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: linear-gradient(
    90deg,
    var(--color-primary, #1cb0f6),
    var(--color-primary-dark, #0b8fde)
  );
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.3s ease;
}

.chunk-card:hover {
  border-color: var(--color-primary, #1cb0f6);
  border-width: 2px;
  transform: translateY(-4px);
}

.chunk-card:hover::before {
  transform: scaleX(1);
}

.chunk-number {
  font-size: 48px;
  font-weight: bold;
  color: var(--color-primary, #1cb0f6);
  margin-bottom: 10px;
}

.chunk-title {
  font-size: 18px;
  font-weight: 600;
  color: var(--color-text-dark, #1a1a1a);
  margin-bottom: 5px;
}

.chunk-range {
  font-size: 14px;
  color: var(--color-text-muted, #6b7280);
  margin-bottom: 10px;
}

.chunk-description {
  font-size: 14px;
  color: var(--color-text-body, #2c2c2c);
  font-style: italic;
}

/* ============================================
   Recommended Section
   ============================================ */

.recommended-badge {
  display: inline-block;
  background: linear-gradient(135deg, var(--color-accent-gold, #ffe66d), #ffed4e);
  color: var(--color-text-dark, #1a1a1a);
  padding: 8px 16px;
  border-radius: 20px;
  font-size: 14px;
  font-weight: 600;
  margin-bottom: 20px;
}

.recommended-box {
  background: linear-gradient(135deg, var(--color-accent-gold, #ffe66d) 0%, #fff8dc 100%);
  border: 2px solid var(--color-secondary, #ff7d00);
  border-radius: 8px;
  padding: 30px;
  margin-bottom: 30px;
}

.recommended-box h2 {
  color: var(--color-text-dark, #1a1a1a);
  margin-bottom: 15px;
  font-size: 28px;
}

.rec-why {
  color: var(--color-text-body, #2c2c2c);
  font-size: 16px;
  line-height: 1.6;
  margin-bottom: 25px;
}

.rec-buttons {
  display: flex;
  gap: 15px;
  flex-wrap: wrap;
  align-items: center;
}

/* ============================================
   Techniques Grid
   ============================================ */

.alternatives-section {
  margin-top: 40px;
  padding-top: 30px;
  border-top: 2px solid var(--color-bg-light, #f0f2f5);
}

.alternatives-section h3 {
  font-size: 22px;
  color: var(--color-text-dark, #1a1a1a);
  margin-bottom: 10px;
}

.techniques-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 15px;
  margin: 25px 0;
}

.technique-option {
  background: white;
  border: 2px solid #ddd;
  border-radius: 8px;
  padding: 20px;
  cursor: pointer;
  transition: all 0.3s ease;
  text-align: center;
  position: relative;
}

.technique-option:hover {
  border-color: var(--color-primary, #1cb0f6);
  border-width: 2px;
  background: #f8f9ff;
}

.technique-option.recommended {
  border-color: var(--color-accent-gold, #ffe66d);
  background: #fffacd;
}

.tech-icon {
  font-size: 36px;
  color: var(--color-primary, #1cb0f6);
  margin-bottom: 10px;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 50px;
  background: linear-gradient(
    135deg,
    var(--color-primary-light, #5ec5f8),
    var(--color-bg-light, #f0f2f5)
  );
  border-radius: 8px;
}

.tech-name {
  font-size: 16px;
  font-weight: 600;
  color: var(--color-text-dark, #1a1a1a);
  margin-bottom: 8px;
}

.tech-desc {
  font-size: 14px;
  color: var(--color-text-muted, #6b7280);
  line-height: 1.4;
}

/* ============================================
   Buttons
   ============================================ */

.btn {
  padding: 12px 24px;
  border: none;
  border-radius: 6px;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.3s ease;
  text-transform: none;
}

.btn-primary {
  background: linear-gradient(
    135deg,
    var(--color-primary, #1cb0f6),
    var(--color-primary-dark, #0b8fde)
  );
  color: white;
}

.btn-primary:hover {
  transform: translateY(-2px);
  border-color: rgba(28, 176, 246, 0.5);
}

.btn-primary:active {
  transform: translateY(0);
}

.btn-secondary {
  background: var(--color-bg-light, #f0f2f5);
  color: var(--color-text-dark, #1a1a1a);
  margin-top: 20px;
}

.btn-secondary:hover {
  background: var(--color-bg-soft, #f8f9fa);
}

.btn-link {
  background: none;
  color: var(--color-primary, #1cb0f6);
  text-decoration: underline;
  padding: 8px 12px;
  cursor: pointer;
}

.btn-link:hover {
  color: var(--color-primary-dark, #0b8fde);
}

/* ============================================
   Responsive Design
   ============================================ */

@media (max-width: 768px) {
  .app-header {
    padding: 20px 15px;
  }

  .app-header h1 {
    font-size: 24px;
  }

  .screen-content {
    padding: 25px 15px;
  }

  .chunks-grid {
    grid-template-columns: 1fr;
    gap: 15px;
  }

  .techniques-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .rec-buttons {
    flex-direction: column;
  }

  .rec-buttons .btn {
    width: 100%;
  }
}

@media (max-width: 480px) {
  body {
    font-size: 14px;
  }

  .app-header h1 {
    font-size: 20px;
  }

  .screen-content h2 {
    font-size: 22px;
  }

  .chunk-number {
    font-size: 36px;
  }

  .recommended-box {
    padding: 20px;
  }

  .recommended-box h2 {
    font-size: 22px;
  }

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

/* ============================================
   Accessibility
   ============================================ */

.btn:focus,
.chunk-card:focus,
.technique-option:focus {
  outline: 2px solid #667eea;
  outline-offset: 2px;
}

/* ============================================
   Utility Classes
   ============================================ */

.text-center {
  text-align: center;
}

.mt-3 {
  margin-top: 30px;
}

.mb-3 {
  margin-bottom: 30px;
}