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

:root {
  --primary: #5b8def;
  --primary-dark: #4a7bd4;
  --danger: #ff6b6b;
  --success: #51cf66;
  --bg: #f5f7fa;
  --card: #ffffff;
  --text: #2d3436;
  --text-muted: #888;
  --border: #e8ecf0;
  --shadow: 0 2px 12px rgba(0,0,0,0.08);
  --radius: 12px;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  overflow-x: hidden;
}

.page {
  display: none;
  width: 100%;
  min-height: 100vh;
}

.page.active {
  display: flex;
}

.hidden {
  display: none !important;
}

.login-container {
  margin: auto;
  text-align: center;
  padding: 2rem;
}

.login-container h1 {
  font-size: 2.5rem;
  margin-bottom: 0.5rem;
  color: var(--primary);
}

.login-container p {
  color: var(--text-muted);
  margin-bottom: 2rem;
}

.login-form {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  max-width: 320px;
  margin: 0 auto;
  background: var(--card);
  padding: 2rem;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.login-hint {
  margin-top: 1rem;
  font-size: 0.85rem;
  color: var(--text-muted);
}

.login-form input:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

.login-form input {
  padding: 0.8rem 1rem;
  border: 1.5px solid var(--border);
  border-radius: 8px;
  background: var(--bg);
  color: var(--text);
  font-size: 1rem;
  outline: none;
  transition: border-color 0.3s;
}

.login-form input:focus {
  border-color: var(--primary);
}

.register-link {
  display: block;
  text-align: center;
  color: var(--primary);
  text-decoration: none;
  font-size: 0.9rem;
  padding: 0.5rem;
}

.register-link:hover {
  text-decoration: underline;
}

button {
  cursor: pointer;
  border: none;
  border-radius: 8px;
  font-size: 1rem;
  padding: 0.7rem 1.2rem;
  transition: all 0.2s;
}

button:active {
  transform: scale(0.97);
}

#login-btn, #reg-submit-btn {
  background: var(--primary);
  color: white;
  font-size: 1.1rem;
  padding: 0.9rem;
  border-radius: 8px;
}

#login-btn:hover, #reg-submit-btn:hover {
  background: var(--primary-dark);
}

.lobby-layout {
  width: 100%;
  display: flex;
  flex-direction: column;
  height: 100vh;
}

.lobby-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.8rem 1.5rem;
  background: var(--card);
  border-bottom: 1px solid var(--border);
  box-shadow: 0 1px 4px rgba(0,0,0,0.04);
}

.lobby-header h2 {
  font-size: 1.2rem;
  color: var(--primary);
}

.user-info {
  display: flex;
  align-items: center;
  gap: 0.8rem;
}

#current-user {
  font-weight: 600;
  color: var(--text);
}

#user-stats {
  color: var(--text-muted);
  font-size: 0.85rem;
}

#logout-btn {
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--text-muted);
  padding: 0.4rem 0.8rem;
  font-size: 0.85rem;
  border-radius: 6px;
}

.lobby-content {
  display: flex;
  flex: 1;
  overflow: hidden;
}

.lobby-main {
  flex: 1;
  padding: 1.5rem;
  overflow-y: auto;
}

.lobby-sidebar {
  width: 320px;
  border-left: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  background: var(--card);
}

.sidebar-tabs {
  display: flex;
  border-bottom: 1px solid var(--border);
}

.tab-btn {
  flex: 1;
  padding: 0.7rem;
  background: var(--bg);
  color: var(--text-muted);
  font-size: 0.9rem;
  border-radius: 0;
  border: none;
  border-bottom: 2px solid transparent;
  position: relative;
}

.tab-btn.active {
  background: var(--card);
  color: var(--primary);
  border-bottom-color: var(--primary);
  font-weight: 600;
}

.sidebar-panel {
  flex: 1;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.mode-selection {
  margin-bottom: 1.5rem;
}

.mode-selection h3,
.game-settings h3 {
  margin-bottom: 0.8rem;
  font-size: 1rem;
  color: var(--text);
}

.mode-buttons {
  display: flex;
  gap: 0.8rem;
  flex-wrap: wrap;
}

.mode-btn {
  padding: 0.9rem 1.5rem;
  background: var(--card);
  border: 1.5px solid var(--border);
  color: var(--text);
  font-size: 1rem;
  font-weight: 500;
  min-width: 120px;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

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

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

.game-settings {
  background: var(--card);
  padding: 1.5rem;
  border-radius: var(--radius);
  margin-bottom: 1.5rem;
  box-shadow: var(--shadow);
}

.setting-group {
  margin-bottom: 1rem;
}

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

.setting-options {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
}

.opt-btn {
  padding: 0.5rem 1rem;
  background: var(--bg);
  border: 1.5px solid var(--border);
  color: var(--text);
  font-size: 0.9rem;
  border-radius: 8px;
}

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

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

.action-btn {
  background: var(--primary);
  color: white;
  padding: 0.7rem 1.3rem;
  font-size: 0.95rem;
  margin-top: 0.5rem;
  margin-right: 0.5rem;
  border-radius: 8px;
}

.action-btn:hover {
  background: var(--primary-dark);
}

.action-btn.danger {
  background: var(--danger);
}

.action-btn.danger:hover {
  background: #e05555;
}

.small-btn {
  padding: 0.3rem 0.6rem;
  font-size: 0.8rem;
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--text-muted);
  border-radius: 6px;
}

#room-list {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  max-height: 300px;
  overflow-y: auto;
}

.room-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.8rem 1rem;
  background: var(--card);
  border-radius: var(--radius);
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
}

.room-item-info {
  display: flex;
  flex-direction: column;
  gap: 0.2rem;
}

.room-item-host {
  font-weight: 600;
}

.room-item-details {
  font-size: 0.8rem;
  color: var(--text-muted);
}

.room-join-btn {
  background: var(--success);
  color: white;
  padding: 0.5rem 1rem;
  border-radius: 8px;
}

.matching-animation {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 1.1rem;
  padding: 1rem 0;
  color: var(--primary);
}

.dots span {
  animation: blink 1.4s infinite;
  font-size: 2rem;
}

.dots span:nth-child(2) { animation-delay: 0.2s; }
.dots span:nth-child(3) { animation-delay: 0.4s; }

@keyframes blink {
  0%, 20% { opacity: 0; }
  50% { opacity: 1; }
  100% { opacity: 0; }
}

#leaderboard-section {
  margin-top: 1.5rem;
}

#leaderboard {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
  max-height: 200px;
  overflow-y: auto;
}

.lb-item {
  display: flex;
  justify-content: space-between;
  padding: 0.5rem 0.8rem;
  background: var(--card);
  border-radius: 8px;
  font-size: 0.9rem;
  border: 1px solid var(--border);
}

.lb-rank {
  width: 30px;
  color: var(--text-muted);
}

.lb-name {
  flex: 1;
}

.lb-stats {
  color: var(--text-muted);
}

.online-users-section {
  margin-top: 1.5rem;
}

#online-users-list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
}

.online-user-tag {
  padding: 0.3rem 0.6rem;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 20px;
  font-size: 0.85rem;
}

.chat-messages {
  flex: 1;
  overflow-y: auto;
  padding: 0.8rem;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.chat-msg {
  padding: 0.4rem 0.6rem;
  border-radius: 8px;
  font-size: 0.85rem;
  word-break: break-word;
  background: var(--bg);
}

.chat-msg .msg-time {
  color: var(--text-muted);
  font-size: 0.75rem;
  margin-right: 0.3rem;
}

.chat-msg .msg-user {
  color: var(--primary);
  font-weight: 600;
  margin-right: 0.4rem;
}

.chat-msg .msg-text {
  color: var(--text);
}

.chat-msg.system-msg {
  color: var(--text-muted);
  font-style: italic;
  text-align: center;
  background: none;
}

.chat-msg.pm-mine {
  background: #e8f4fd;
}

.chat-input-area {
  display: flex;
  padding: 0.8rem;
  gap: 0.5rem;
  border-top: 1px solid var(--border);
}

.chat-input-area input {
  flex: 1;
  padding: 0.6rem;
  border: 1.5px solid var(--border);
  border-radius: 8px;
  background: var(--bg);
  color: var(--text);
  font-size: 0.9rem;
  outline: none;
}

.chat-input-area input:focus {
  border-color: var(--primary);
}

.chat-input-area button {
  background: var(--primary);
  color: white;
  padding: 0.6rem 1rem;
  border-radius: 8px;
}

.game-layout {
  width: 100%;
  height: 100vh;
  display: flex;
  flex-direction: column;
}

.game-info-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.8rem 1.5rem;
  background: var(--card);
  border-bottom: 1px solid var(--border);
  box-shadow: 0 1px 4px rgba(0,0,0,0.04);
  flex-shrink: 0;
}

.player-info {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.player-name {
  font-weight: 600;
  font-size: 0.95rem;
  padding: 0.2rem 0.6rem;
  border-radius: 6px;
}

.player-score {
  background: var(--primary);
  color: white;
  padding: 0.2rem 0.5rem;
  border-radius: 6px;
  font-weight: 600;
  font-size: 0.85rem;
}

.player1-info .player-name {
  background: #333;
  color: white;
}

.player2-info .player-name {
  background: #f0f0f0;
  color: #333;
  border: 1px solid #ddd;
}

.game-status {
  display: flex;
  flex-direction: column;
  align-items: center;
  font-size: 0.85rem;
}

#game-round {
  color: var(--text-muted);
}

#game-turn {
  color: var(--primary);
  font-weight: 600;
}

.game-main-area {
  flex: 1;
  display: flex;
  overflow: hidden;
  min-height: 0;
}

.board-container {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
  min-height: 0;
  min-width: 0;
  overflow: hidden;
}

#game-board {
  display: block;
  touch-action: none;
  border-radius: 8px;
  box-shadow: var(--shadow);
}

.game-chat {
  width: 260px;
  border-left: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  background: var(--card);
  flex-shrink: 0;
}

.game-chat h4 {
  padding: 0.8rem;
  border-bottom: 1px solid var(--border);
  font-size: 0.9rem;
  color: var(--text-muted);
}

.game-controls {
  display: flex;
  justify-content: center;
  gap: 0.8rem;
  padding: 0.8rem;
  background: var(--card);
  border-top: 1px solid var(--border);
  flex-shrink: 0;
  flex-wrap: wrap;
}

#sound-toggle-btn {
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 0.5rem 0.8rem;
  font-size: 0.85rem;
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
}

#sound-toggle-btn svg {
  vertical-align: middle;
  flex-shrink: 0;
}

#toast-container {
  position: fixed;
  top: 1rem;
  right: 1rem;
  z-index: 9999;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.toast {
  padding: 0.8rem 1.2rem;
  border-radius: var(--radius);
  background: var(--card);
  border: 1px solid var(--border);
  color: var(--text);
  animation: slideIn 0.3s ease;
  max-width: 300px;
  box-shadow: var(--shadow);
}

.toast.error {
  border-color: var(--danger);
  background: #fff5f5;
  color: var(--danger);
}

.toast.success {
  border-color: var(--success);
  background: #f0fff4;
  color: #2b8a3e;
}

@keyframes slideIn {
  from { transform: translateX(100%); opacity: 0; }
  to { transform: translateX(0); opacity: 1; }
}

#modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.4);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 10000;
}

#modal-content {
  background: var(--card);
  padding: 2rem;
  border-radius: 16px;
  text-align: center;
  max-width: 380px;
  width: 90%;
  box-shadow: 0 8px 32px rgba(0,0,0,0.15);
}

#modal-title {
  font-size: 1.4rem;
  margin-bottom: 0.6rem;
  color: var(--text);
}

#modal-message {
  color: var(--text-muted);
  margin-bottom: 1.5rem;
  line-height: 1.5;
}

#modal-buttons {
  display: flex;
  gap: 0.8rem;
  justify-content: center;
  flex-wrap: wrap;
}

#modal-buttons button {
  min-width: 100px;
}

.friend-add-area {
  display: flex;
  padding: 0.8rem;
  gap: 0.5rem;
  border-bottom: 1px solid var(--border);
}

.friend-add-area input {
  flex: 1;
  padding: 0.5rem 0.8rem;
  border: 1.5px solid var(--border);
  border-radius: 8px;
  background: var(--bg);
  color: var(--text);
  font-size: 0.85rem;
  outline: none;
}

.friend-add-area input:focus {
  border-color: var(--primary);
}

.friend-add-area button {
  background: var(--primary);
  color: white;
  padding: 0.5rem 0.8rem;
  font-size: 0.85rem;
  border-radius: 8px;
}

#friend-requests {
  padding: 0.5rem 0.8rem;
}

#friend-requests h4 {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 0.4rem;
}

.request-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.5rem 0;
  border-bottom: 1px solid var(--border);
}

.request-from {
  font-weight: 600;
  font-size: 0.9rem;
}

.request-actions {
  display: flex;
  gap: 0.3rem;
}

.req-accept-btn {
  background: var(--success);
  color: white;
  padding: 0.3rem 0.6rem;
  font-size: 0.8rem;
  border-radius: 6px;
}

.req-reject-btn {
  background: var(--danger);
  color: white;
  padding: 0.3rem 0.6rem;
  font-size: 0.8rem;
  border-radius: 6px;
}

#friends-list {
  flex: 1;
  overflow-y: auto;
  padding: 0.5rem 0.8rem;
}

.empty-hint {
  color: var(--text-muted);
  font-size: 0.85rem;
  text-align: center;
  padding: 1rem 0;
}

.friend-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.6rem 0;
  border-bottom: 1px solid var(--border);
}

.friend-item-info {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.friend-status {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  display: inline-block;
}

.friend-status.online {
  background: var(--success);
}

.friend-status.offline {
  background: #ccc;
}

.friend-name {
  font-size: 0.9rem;
  font-weight: 500;
}

.unread-badge {
  background: var(--danger);
  color: white;
  font-size: 0.7rem;
  font-weight: 600;
  padding: 0.1rem 0.4rem;
  border-radius: 10px;
  min-width: 18px;
  text-align: center;
  line-height: 1.3;
}

.tab-badge {
  background: var(--danger);
  color: white;
  font-size: 0.65rem;
  font-weight: 600;
  padding: 0.1rem 0.35rem;
  border-radius: 10px;
  min-width: 16px;
  text-align: center;
  line-height: 1.2;
  margin-left: 0.3rem;
  vertical-align: middle;
}

.friend-item-actions {
  display: flex;
  gap: 0.3rem;
}

.friend-chat-btn {
  background: var(--primary);
  color: white;
  padding: 0.25rem 0.6rem;
  font-size: 0.8rem;
  border-radius: 6px;
}

.friend-del-btn {
  background: var(--bg);
  color: var(--text-muted);
  border: 1px solid var(--border);
  padding: 0.25rem 0.6rem;
  font-size: 0.8rem;
  border-radius: 6px;
}

#pm-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.3);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 9500;
}

#pm-window {
  width: 400px;
  max-width: 90vw;
  height: 500px;
  max-height: 80vh;
  background: var(--card);
  border-radius: 16px;
  box-shadow: 0 8px 32px rgba(0,0,0,0.15);
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.pm-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.8rem 1rem;
  border-bottom: 1px solid var(--border);
  background: var(--bg);
}

.pm-header span {
  font-weight: 600;
  font-size: 1rem;
}

#pm-close-btn {
  background: none;
  color: var(--text-muted);
  font-size: 1.2rem;
  padding: 0.2rem 0.5rem;
  border-radius: 6px;
}

#pm-close-btn:hover {
  background: var(--border);
}

#pm-messages {
  flex: 1;
  overflow-y: auto;
  padding: 0.8rem;
}

@media (max-width: 768px) {
  .lobby-content {
    flex-direction: column;
  }

  .lobby-sidebar {
    width: 100%;
    border-left: none;
    border-top: 1px solid var(--border);
    max-height: 280px;
  }

  .lobby-header {
    flex-direction: column;
    gap: 0.5rem;
    padding: 0.6rem 1rem;
  }

  .lobby-header h2 {
    font-size: 1rem;
  }

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

  .mode-btn {
    width: 100%;
    min-width: unset;
  }

  .setting-options {
    flex-wrap: wrap;
  }

  .opt-btn {
    flex: 1;
    min-width: 60px;
    text-align: center;
  }

  .game-layout {
    height: 100dvh;
  }

  .game-main-area {
    flex-direction: column;
  }

  .board-container {
    flex: 1;
    width: 100%;
    height: auto;
    padding: 0.3rem;
    min-height: 0;
  }

  .game-chat {
    width: 100%;
    border-left: none;
    border-top: 1px solid var(--border);
    max-height: 150px;
    min-height: 100px;
  }

  .game-info-bar {
    padding: 0.5rem 0.8rem;
    font-size: 0.8rem;
  }

  .player-name {
    font-size: 0.8rem;
    padding: 0.15rem 0.4rem;
  }

  .player-score {
    font-size: 0.75rem;
    padding: 0.15rem 0.4rem;
  }

  .game-controls {
    padding: 0.5rem;
    gap: 0.5rem;
  }

  .game-controls button {
    padding: 0.5rem 0.7rem;
    font-size: 0.8rem;
  }

  .login-container h1 {
    font-size: 2rem;
  }

  #online-options {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
  }

  .room-item {
    flex-direction: column;
    gap: 0.5rem;
    align-items: flex-start;
  }

  .room-join-btn {
    width: 100%;
  }

  #pm-window {
    height: 70vh;
  }
}

.uc-layout {
  width: 100%;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.uc-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.8rem 1.5rem;
  background: var(--card);
  border-bottom: 1px solid var(--border);
  box-shadow: 0 1px 4px rgba(0,0,0,0.04);
}

.uc-header h2 {
  font-size: 1.2rem;
  color: var(--primary);
}

.uc-content {
  flex: 1;
  padding: 1.5rem;
  max-width: 800px;
  margin: 0 auto;
  width: 100%;
}

.uc-card {
  background: var(--card);
  padding: 1.5rem;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  margin-bottom: 1.5rem;
}

.uc-card h3 {
  margin-bottom: 1rem;
  font-size: 1.1rem;
  color: var(--text);
}

.uc-info-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 1rem;
}

.uc-info-item {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
}

.uc-label {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.uc-value {
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--text);
}

.uc-form {
  display: flex;
  flex-direction: column;
  gap: 0.8rem;
  max-width: 400px;
}

.uc-form input {
  padding: 0.8rem 1rem;
  border: 1.5px solid var(--border);
  border-radius: 8px;
  background: var(--bg);
  color: var(--text);
  font-size: 1rem;
  outline: none;
}

.uc-form input:focus {
  border-color: var(--primary);
}

.uc-history {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
  max-height: 400px;
  overflow-y: auto;
}

.history-item {
  display: flex;
  align-items: center;
  gap: 0.8rem;
  padding: 0.6rem 0.8rem;
  background: var(--bg);
  border-radius: 8px;
  font-size: 0.9rem;
}

.history-result {
  padding: 0.2rem 0.6rem;
  border-radius: 6px;
  font-weight: 600;
  font-size: 0.85rem;
}

.history-result.win {
  background: #e6f9ed;
  color: #2b8a3e;
}

.history-result.loss {
  background: #fff0f0;
  color: #e03131;
}

.history-result.draw {
  background: #f0f0f0;
  color: #666;
}

.history-opponent {
  flex: 1;
  font-weight: 500;
}

.history-size {
  color: var(--text-muted);
  font-size: 0.8rem;
}

.history-time {
  color: var(--text-muted);
  font-size: 0.8rem;
}

#user-center-btn {
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--text-muted);
  padding: 0.4rem 0.8rem;
  font-size: 0.85rem;
  border-radius: 6px;
  cursor: pointer;
}

#user-center-btn:hover {
  border-color: var(--primary);
  color: var(--primary);
}

@media (max-width: 768px) {
  .uc-content {
    padding: 1rem;
  }

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

  .history-item {
    flex-wrap: wrap;
    gap: 0.4rem;
  }
}

@media (max-width: 480px) {
  .uc-card {
    padding: 1rem;
  }

  .uc-info-grid {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 480px) {
  .lobby-main {
    padding: 1rem;
  }

  .game-settings {
    padding: 1rem;
  }

  .opt-btn {
    padding: 0.4rem 0.6rem;
    font-size: 0.8rem;
  }

  .login-form {
    padding: 1.5rem;
  }
}