:root {
  --primary: #2563eb;
  --primary-light: #3b82f6;
  --primary-dark: #1d4ed8;
  --bg-main: #ffffff;
  --bg-secondary: #f8fafc;
  --bg-tertiary: #f1f5f9;
  --text-primary: #0f172a;
  --text-secondary: #64748b;
  --text-tertiary: #cbd5e1;
  --border-color: #e2e8f0;
  --border-color-light: #f1f5f9;
  --shadow-sm: 0 4px 12px rgba(15, 23, 42, 0.06);
  --shadow-md: 0 12px 24px rgba(15, 23, 42, 0.1);
  --shadow-lg: 0 20px 40px rgba(15, 23, 42, 0.15);
}

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

html, body {
  height: 100%;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  background: linear-gradient(135deg, #f0f4f8 0%, #d9e2ec 100%);
  color: var(--text-primary);
  overflow: hidden;
}

.app-container {
  height: 100vh;
  display: flex;
  flex-direction: column;
  background: var(--bg-main);
  max-width: 1000px;
  margin: 0 auto;
  box-shadow: var(--shadow-lg);
}

/* HEADER */
.header {
  flex-shrink: 0;
  background: var(--bg-main);
  border-bottom: 1px solid var(--border-color);
  padding: 18px 24px;
  backdrop-filter: blur(10px);
  animation: slideDown 0.4s ease-out;
}

.header__content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  max-width: 100%;
  gap: 18px;
}

.header__user {
  display: flex;
  align-items: center;
  gap: 14px;
}

.header__actions {
  display: flex;
  align-items: center;
  gap: 18px;
}

.tabs {
  display: flex;
  gap: 10px;
  background: #f8fafc;
  border: 1px solid var(--border-color);
  border-radius: 999px;
  padding: 6px;
}

.tab {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 10px 16px;
  border-radius: 999px;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-secondary);
  text-decoration: none;
  transition: all 0.2s ease;
}

.tab:hover {
  background: #eef2ff;
  color: var(--primary);
}

.tab--active {
  background: linear-gradient(135deg, var(--primary-light) 0%, var(--primary) 100%);
  color: white;
}

.avatar {
  width: 56px;
  height: 56px;
  border-radius: 50%;
  background: linear-gradient(135deg, #3b82f6 0%, #2563eb 100%);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.3rem;
  font-weight: 700;
  color: white;
  box-shadow: var(--shadow-sm);
  animation: popIn 0.5s ease-out;
}

.user-info {
  animation: fadeIn 0.5s ease-out 0.1s backwards;
}

.user-label {
  font-size: 0.75rem;
  color: var(--text-tertiary);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 2px;
  font-weight: 600;
}

.user-name {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text-primary);
}

.header__status {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 14px;
  border-radius: 20px;
  background: #f0fdf4;
  animation: fadeIn 0.5s ease-out 0.2s backwards;
}

.status-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: #16a34a;
  animation: pulse 2s infinite;
}

.status-text {
  font-size: 0.9rem;
  color: #16a34a;
  font-weight: 600;
}

/* CHAT WRAPPER */
.chat-wrapper {
  flex: 1;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.messages-container {
  flex: 1;
  overflow-y: auto;
  padding: 20px 24px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  background: linear-gradient(180deg, var(--bg-main) 0%, var(--bg-secondary) 100%);
}

.messages-container::-webkit-scrollbar {
  width: 8px;
}

.messages-container::-webkit-scrollbar-track {
  background: transparent;
}

.messages-container::-webkit-scrollbar-thumb {
  background: var(--border-color);
  border-radius: 4px;
}

.messages-container::-webkit-scrollbar-thumb:hover {
  background: var(--text-tertiary);
}

.empty-state {
  margin: auto;
  text-align: center;
  color: var(--text-secondary);
  animation: fadeIn 0.6s ease-out;
}

.empty-icon {
  font-size: 4rem;
  margin-bottom: 12px;
  animation: bounce 2s infinite;
}

.empty-state p {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 6px;
}

.empty-state span {
  font-size: 0.95rem;
  color: var(--text-tertiary);
}

/* MESSAGES */
.message {
  max-width: 75%;
  padding: 12px 16px;
  border-radius: 16px;
  font-size: 0.95rem;
  line-height: 1.5;
  animation: slideIn 0.3s ease-out;
  word-wrap: break-word;
}

.message.incoming {
  align-self: flex-start;
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color-light);
  color: var(--text-primary);
}

.message.outgoing {
  align-self: flex-end;
  background: linear-gradient(135deg, var(--primary-light) 0%, var(--primary) 100%);
  color: white;
  box-shadow: var(--shadow-sm);
}

.message-meta {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 8px;
  margin-top: 6px;
  font-size: 0.8rem;
}

.message-author {
  font-weight: 600;
  opacity: 0.9;
}

.message-time {
  opacity: 0.7;
  font-size: 0.75rem;
}

/* INPUT SECTION */
.input-section {
  flex-shrink: 0;
  padding: 16px 24px;
  background: var(--bg-main);
  border-top: 1px solid var(--border-color);
  animation: slideUp 0.4s ease-out;
}

.nickname-setup {
  display: flex;
  gap: 10px;
  animation: fadeIn 0.5s ease-out;
}

.nickname-input {
  flex: 1;
  padding: 12px 16px;
  border: 1.5px solid var(--border-color);
  border-radius: 12px;
  font-size: 0.95rem;
  color: var(--text-primary);
  background: var(--bg-secondary);
  transition: all 0.2s ease;
}

.nickname-input:focus {
  outline: none;
  border-color: var(--primary);
  background: var(--bg-main);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.join-btn {
  padding: 12px 24px;
  border: none;
  border-radius: 12px;
  background: linear-gradient(135deg, var(--primary-light) 0%, var(--primary) 100%);
  color: white;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s ease;
  box-shadow: var(--shadow-sm);
}

.join-btn:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
}

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

.message-form {
  display: flex;
  gap: 10px;
  animation: fadeIn 0.5s ease-out;
}

.message-input {
  flex: 1;
  padding: 12px 16px;
  border: 1.5px solid var(--border-color);
  border-radius: 12px;
  font-size: 0.95rem;
  color: var(--text-primary);
  background: var(--bg-secondary);
  transition: all 0.2s ease;
}

.message-input:focus {
  outline: none;
  border-color: var(--primary);
  background: var(--bg-main);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.send-btn {
  width: 44px;
  height: 44px;
  border: none;
  border-radius: 12px;
  background: linear-gradient(135deg, var(--primary-light) 0%, var(--primary) 100%);
  color: white;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s ease;
  box-shadow: var(--shadow-sm);
}

.send-btn:hover:not(:disabled) {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
}

.send-btn:active:not(:disabled) {
  transform: translateY(0);
}

.send-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.send-icon {
  font-size: 1.2rem;
  display: inline-block;
}

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

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

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

@keyframes fadeIn {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

@keyframes popIn {
  0% {
    transform: scale(0.8);
    opacity: 0;
  }
  60% {
    transform: scale(1.1);
  }
  100% {
    transform: scale(1);
    opacity: 1;
  }
}

@keyframes pulse {
  0%, 100% {
    opacity: 1;
  }
  50% {
    opacity: 0.6;
  }
}

@keyframes bounce {
  0%, 100% {
    transform: translateY(0);
  }
  50% {
    transform: translateY(-8px);
  }
}

/* RESPONSIVE */
@media (max-width: 768px) {
  .app-container {
    border-radius: 0;
    height: 100vh;
  }

  .message {
    max-width: 85%;
  }

  .header {
    padding: 14px 16px;
  }

  .chat-wrapper {
    padding: 0;
  }

  .messages-container {
    padding: 16px;
  }

  .input-section {
    padding: 12px 16px;
  }
}