/* ==================== GLOBAL STYLES ==================== */
:root {
  --primary-color: #6366f1;
  --primary-dark: #4f46e5;
  --secondary-color: #8b5cf6;
  --success-color: #10b981;
  --danger-color: #ef4444;
  --warning-color: #f59e0b;
  --background: #0f172a;
  --surface: #1e293b;
  --surface-light: #334155;
  --text-primary: #ffffff;
  --text-secondary: #cbd5e1;
  --border-color: #475569;
  --spacing: 1rem;
  --border-radius: 12px;
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
  --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html, body {
  height: 100%;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', sans-serif;
  background: var(--background);
  color: var(--text-primary);
  line-height: 1.6;
  overflow-x: hidden;
  padding-bottom: 80px;
}

/* ==================== HEADER ==================== */
.app-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
  padding: 1rem;
  box-shadow: var(--shadow);
}

.header-content {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  font-size: 1.5rem;
  font-weight: 700;
  letter-spacing: -0.5px;
}

.menu-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: transparent;
  border: none;
  cursor: pointer;
  padding: 8px;
}

.menu-toggle span {
  width: 25px;
  height: 3px;
  background: white;
  border-radius: 2px;
  transition: var(--transition);
}

.menu-toggle.active span:nth-child(1) {
  transform: rotate(45deg) translate(10px, 10px);
}

.menu-toggle.active span:nth-child(2) {
  opacity: 0;
}

.menu-toggle.active span:nth-child(3) {
  transform: rotate(-45deg) translate(8px, -8px);
}

/* ==================== MAIN CONTENT ==================== */
.app-main {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0;
}

.container {
  padding: 2rem 1rem;
}

.page {
  display: none;
  animation: fadeIn 0.4s ease-in-out;
}

.page.active {
  display: block;
}

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

/* ==================== HOME PAGE ==================== */
.home-hero {
  text-align: center;
  margin-bottom: 3rem;
  animation: slideDown 0.6s ease-out;
}

@keyframes slideDown {
  from {
    opacity: 0;
    transform: translateY(-20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.hero-title {
  font-size: 2.5rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-subtitle {
  font-size: 1.1rem;
  color: var(--text-secondary);
}

/* ==================== CARDS ==================== */
.cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 1.5rem;
  margin-bottom: 3rem;
}

.card {
  background: var(--surface);
  border-radius: var(--border-radius);
  padding: 1.5rem;
  cursor: pointer;
  border: 1px solid var(--border-color);
  transition: var(--transition);
  position: relative;
  overflow: hidden;
}

.card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 4px;
  background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.3s ease;
}

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

.card:hover {
  transform: translateY(-8px);
  box-shadow: var(--shadow);
  border-color: var(--primary-color);
}

.card-icon {
  font-size: 2.5rem;
  margin-bottom: 1rem;
}

.card h3 {
  font-size: 1.25rem;
  margin-bottom: 0.5rem;
}

.card p {
  color: var(--text-secondary);
  font-size: 0.95rem;
  margin-bottom: 1rem;
}

.card-arrow {
  display: inline-block;
  transition: var(--transition);
}

.card:hover .card-arrow {
  transform: translateX(4px);
}

/* ==================== STATS ==================== */
.stats-container {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 1rem;
  padding: 2rem;
  background: var(--surface);
  border-radius: var(--border-radius);
  border: 1px solid var(--border-color);
}

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

.stat-label {
  display: block;
  color: var(--text-secondary);
  font-size: 0.9rem;
  margin-bottom: 0.5rem;
}

.stat-value {
  display: block;
  font-size: 1.8rem;
  font-weight: 700;
  color: var(--primary-color);
}

/* ==================== BUTTONS ==================== */
.btn {
  padding: 0.75rem 1.5rem;
  border: none;
  border-radius: var(--border-radius);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  display: inline-block;
  text-align: center;
  outline: none;
}

.btn-primary {
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  color: white;
  box-shadow: 0 4px 15px rgba(99, 102, 241, 0.3);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(99, 102, 241, 0.4);
}

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

.btn-secondary {
  background: var(--surface-light);
  color: white;
  border: 1px solid var(--border-color);
}

.btn-secondary:hover {
  background: var(--border-color);
}

.btn-large {
  width: 100%;
  padding: 1rem;
  font-size: 1.1rem;
  margin-top: 1rem;
}

/* ==================== FORM ELEMENTS ==================== */
.setup-section {
  margin-bottom: 1.5rem;
}

.setup-section label {
  display: block;
  margin-bottom: 0.5rem;
  font-weight: 600;
  color: var(--text-primary);
}

.setup-input {
  width: 100%;
  padding: 0.75rem;
  background: var(--surface);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  color: var(--text-primary);
  font-size: 1rem;
  transition: var(--transition);
}

.setup-input:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

.button-group {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(100px, 1fr));
  gap: 0.75rem;
}

.mode-btn {
  padding: 0.75rem;
  background: var(--surface);
  border: 2px solid var(--border-color);
  border-radius: var(--border-radius);
  color: var(--text-primary);
  cursor: pointer;
  transition: var(--transition);
  font-weight: 600;
  font-size: 0.9rem;
}

.mode-btn:hover {
  border-color: var(--primary-color);
}

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

/* ==================== PRACTICE PAGE ==================== */
.practice-setup,
.practice-session,
.practice-results {
  animation: fadeIn 0.4s ease-in-out;
}

.hidden {
  display: none !important;
}

.practice-header {
  margin-bottom: 2rem;
}

.progress-info {
  margin-bottom: 1rem;
}

.progress-bar {
  width: 100%;
  height: 8px;
  background: var(--surface);
  border-radius: 4px;
  overflow: hidden;
  margin-top: 0.5rem;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
  transition: width 0.4s ease;
  width: 0%;
}

.practice-timer {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--danger-color);
  text-align: right;
}

.question-card {
  background: var(--surface);
  border-radius: var(--border-radius);
  padding: 2rem;
  margin-bottom: 2rem;
  text-align: center;
  border: 2px solid var(--border-color);
  transition: var(--transition);
}

.question-card:hover {
  border-color: var(--primary-color);
}

.question-text {
  font-size: 2.5rem;
  font-weight: 700;
  margin-bottom: 2rem;
  color: var(--primary-color);
}

.answer-input-group {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
}

.answer-input {
  flex: 1;
  min-width: 150px;
  padding: 1rem;
  background: var(--background);
  border: 2px solid var(--border-color);
  border-radius: var(--border-radius);
  color: var(--text-primary);
  font-size: 1.1rem;
  font-weight: 600;
  transition: var(--transition);
}

.answer-input:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

.answer-input::placeholder {
  color: var(--text-secondary);
}

.feedback {
  padding: 1.5rem;
  border-radius: var(--border-radius);
  margin-bottom: 1rem;
  font-size: 1.1rem;
  font-weight: 600;
  animation: slideDown 0.3s ease-out;
}

.feedback.correct {
  background: rgba(16, 185, 129, 0.1);
  color: var(--success-color);
  border-left: 4px solid var(--success-color);
}

.feedback.wrong {
  background: rgba(239, 68, 68, 0.1);
  color: var(--danger-color);
  border-left: 4px solid var(--danger-color);
}

/* ==================== ARENA PAGE ==================== */
.arena-subtitle {
  color: var(--text-secondary);
  margin-bottom: 2rem;
  font-size: 1.1rem;
}

.arena-info-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 1rem;
  margin-bottom: 2rem;
}

.arena-info-card {
  background: var(--surface);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  padding: 1.5rem;
  text-align: center;
}

.arena-info-label {
  display: block;
  color: var(--text-secondary);
  font-size: 0.9rem;
  margin-bottom: 0.5rem;
}

.arena-info-value {
  display: block;
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--primary-color);
}

.player-name-input {
  margin-bottom: 1rem;
}

.arena-header {
  display: grid;
  grid-template-columns: 120px 1fr;
  gap: 2rem;
  margin-bottom: 2rem;
  align-items: center;
}

.arena-timer-display {
  display: flex;
  justify-content: center;
}

.timer-circle {
  width: 120px;
  height: 120px;
  background: var(--surface);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 4px solid var(--primary-color);
  position: relative;
  overflow: hidden;
}

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

#arenaTimer {
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--primary-color);
  display: block;
}

.arena-stats {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
}

.stat {
  background: var(--surface);
  padding: 1rem;
  border-radius: var(--border-radius);
  text-align: center;
  border: 1px solid var(--border-color);
}

.stat-label {
  color: var(--text-secondary);
  font-size: 0.9rem;
}

.stat-value {
  font-size: 2rem;
  font-weight: 700;
  color: var(--primary-color);
}

/* ==================== RESULTS PAGE ==================== */
.results-summary {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 1rem;
  margin-bottom: 2rem;
}

.result-item {
  background: var(--surface);
  padding: 1.5rem;
  border-radius: var(--border-radius);
  text-align: center;
  border: 1px solid var(--border-color);
}

.result-item span:first-child {
  display: block;
  color: var(--text-secondary);
  font-size: 0.9rem;
  margin-bottom: 0.5rem;
}

.result-value {
  font-size: 1.8rem;
  font-weight: 700;
  color: var(--primary-color);
}

.final-score-display {
  text-align: center;
  margin-bottom: 2rem;
}

.score-circle {
  width: 200px;
  height: 200px;
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto;
  font-size: 4rem;
  font-weight: 700;
  box-shadow: var(--shadow);
  animation: scaleIn 0.5s cubic-bezier(0.34, 1.56, 0.64, 1);
}

@keyframes scaleIn {
  from {
    transform: scale(0);
    opacity: 0;
  }
  to {
    transform: scale(1);
    opacity: 1;
  }
}

/* ==================== LEADERBOARD PAGE ==================== */
.leaderboard-filters {
  display: flex;
  gap: 0.75rem;
  margin-bottom: 2rem;
  flex-wrap: wrap;
}

.filter-btn {
  padding: 0.6rem 1.2rem;
  background: var(--surface);
  border: 2px solid var(--border-color);
  border-radius: var(--border-radius);
  color: var(--text-primary);
  cursor: pointer;
  transition: var(--transition);
  font-weight: 600;
  font-size: 0.9rem;
}

.filter-btn:hover {
  border-color: var(--primary-color);
}

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

.leaderboard-list {
  display: grid;
  gap: 1rem;
}

.leaderboard-item {
  background: var(--surface);
  padding: 1.5rem;
  border-radius: var(--border-radius);
  border: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: var(--transition);
  animation: slideIn 0.3s ease-out;
}

@keyframes slideIn {
  from {
    opacity: 0;
    transform: translateX(-20px);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

.leaderboard-item:hover {
  border-color: var(--primary-color);
  transform: translateX(4px);
}

.leaderboard-rank {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--primary-color);
  min-width: 40px;
}

.leaderboard-info {
  flex: 1;
  margin-left: 1rem;
}

.leaderboard-name {
  font-weight: 600;
  font-size: 1.1rem;
  margin-bottom: 0.25rem;
}

.leaderboard-details {
  color: var(--text-secondary);
  font-size: 0.85rem;
}

.leaderboard-score {
  text-align: right;
  font-weight: 700;
  font-size: 1.3rem;
  color: var(--primary-color);
}

.empty-state {
  text-align: center;
  padding: 3rem;
  color: var(--text-secondary);
  font-size: 1.1rem;
}

/* ==================== ABACUS TOOL ==================== */
.abacus-display {
  background: var(--surface);
  border-radius: var(--border-radius);
  padding: 2rem;
  margin-bottom: 2rem;
  border: 1px solid var(--border-color);
}

.abacus-container {
  display: flex;
  justify-content: center;
  gap: 1rem;
  margin-bottom: 2rem;
  flex-wrap: wrap;
}

.abacus-column {
  width: 80px;
  height: 350px;
  background: var(--background);
  border: 3px solid var(--primary-color);
  border-radius: 8px;
  position: relative;
  padding: 5px;
  display: flex;
  flex-direction: column;
  justify-content: flex-start;
}

.abacus-bead {
  width: 50px;
  height: 30px;
  background: linear-gradient(135deg, #ff9500, #ff7500);
  border-radius: 15px;
  margin: 5px auto;
  cursor: pointer;
  user-select: none;
  transition: all 0.2s cubic-bezier(0.34, 1.56, 0.64, 1);
  position: absolute;
  left: 15px;
  box-shadow: 0 4px 12px rgba(255, 165, 0, 0.3);
}

.abacus-bead:hover {
  transform: scale(1.05);
  box-shadow: 0 6px 16px rgba(255, 165, 0, 0.5);
}

.abacus-bead.active {
  background: linear-gradient(135deg, #ef4444, #dc2626);
  box-shadow: 0 4px 12px rgba(239, 68, 68, 0.3);
}

.abacus-value-display {
  text-align: center;
  margin-bottom: 2rem;
  padding: 1.5rem;
  background: var(--background);
  border-radius: var(--border-radius);
  border: 2px solid var(--primary-color);
}

.value-label {
  display: block;
  color: var(--text-secondary);
  margin-bottom: 0.5rem;
  font-size: 0.95rem;
}

.value-number {
  display: block;
  font-size: 3rem;
  font-weight: 700;
  color: var(--primary-color);
  font-variant-numeric: tabular-nums;
}

.abacus-controls {
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
}

.abacus-guide {
  background: var(--surface);
  padding: 1.5rem;
  border-radius: var(--border-radius);
  border-left: 4px solid var(--primary-color);
  margin-top: 2rem;
}

.abacus-guide h3 {
  margin-bottom: 0.5rem;
  color: var(--primary-color);
}

.abacus-guide p {
  color: var(--text-secondary);
}

/* ==================== BOTTOM NAVIGATION ==================== */
.bottom-nav {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  background: var(--surface);
  border-top: 2px solid var(--border-color);
  display: flex;
  justify-content: space-around;
  z-index: 99;
  max-width: 100vw;
}

.nav-btn {
  flex: 1;
  padding: 0.75rem;
  background: transparent;
  border: none;
  color: var(--text-secondary);
  cursor: pointer;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.3rem;
  font-size: 0.75rem;
  transition: var(--transition);
  border-top: 3px solid transparent;
}

.nav-btn:hover {
  color: var(--primary-color);
}

.nav-btn.active {
  color: var(--primary-color);
  border-top-color: var(--primary-color);
}

.nav-icon {
  font-size: 1.5rem;
}

.nav-label {
  font-weight: 600;
}

/* ==================== RESPONSIVE DESIGN ==================== */
@media (max-width: 768px) {
  .hero-title {
    font-size: 1.8rem;
  }

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

  .container {
    padding: 1rem 0.75rem;
  }

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

  .arena-header {
    grid-template-columns: 1fr;
    text-align: center;
  }

  .leaderboard-item {
    flex-direction: column;
    text-align: center;
  }

  .leaderboard-info {
    margin-left: 0;
    margin-bottom: 0.75rem;
  }

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

@media (max-width: 480px) {
  body {
    padding-bottom: 90px;
  }

  .hero-title {
    font-size: 1.5rem;
  }

  .question-text {
    font-size: 2rem;
  }

  .setup-input {
    width: 100%;
  }

  .answer-input-group {
    flex-direction: column;
  }

  .answer-input {
    width: 100%;
  }

  .abacus-container {
    gap: 0.5rem;
  }

  .abacus-column {
    width: 60px;
    height: 300px;
  }

  .abacus-bead {
    width: 40px;
    height: 24px;
    left: 10px;
  }

  .value-number {
    font-size: 2rem;
  }

  .menu-toggle {
    display: flex;
  }
}