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

:root {
  --white: #ffffff;
  --gray-50: #f9fafb;
  --gray-100: #f3f4f6;
  --gray-200: #e5e7eb;
  --gray-300: #d1d5db;
  --gray-400: #9ca3af;
  --gray-500: #6b7280;
  --gray-600: #4b5563;
  --gray-700: #374151;
  --gray-800: #1f2937;
  --gray-900: #111827;
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow: 0 1px 3px 0 rgb(0 0 0 / 0.1), 0 1px 2px -1px rgb(0 0 0 / 0.1);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
}

html, body {
  height: 100%;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  background-color: var(--gray-50);
  color: var(--gray-800);
  -webkit-font-smoothing: antialiased;
  overflow: hidden;
}

.chat-container {
  display: flex;
  flex-direction: column;
  height: 100%;
  height: 100dvh; /* Dynamic viewport height for mobile */
  max-width: 768px;
  margin: 0 auto;
  background-color: var(--white);
  box-shadow: var(--shadow);
  position: relative;
}

/* Header */
.chat-header {
  position: sticky;
  top: 0;
  z-index: 10;
  padding: 16px 20px;
  background-color: var(--white);
  border-bottom: 1px solid var(--gray-200);
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-shrink: 0;
}

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

.header-spacer {
  width: 36px;
  flex-shrink: 0;
}

.clear-button {
  width: 36px;
  height: 36px;
  border: none;
  border-radius: 50%;
  background-color: transparent;
  color: var(--gray-400);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background-color 0.15s ease, color 0.15s ease;
  flex-shrink: 0;
}

.clear-button:hover {
  background-color: var(--gray-100);
  color: var(--gray-600);
}

.chat-header h1 {
  font-size: 1.5rem;
  font-weight: 600;
  color: var(--gray-900);
  letter-spacing: -0.025em;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 1px;
}

.title-icon {
  width: 28px;
  height: 28px;
}

.chat-header p {
  font-size: 0.875rem;
  color: var(--gray-500);
  margin-top: 2px;
}

.online-status {
  font-size: 0.75rem;
  color: var(--gray-400);
  margin-top: 4px;
}

.online-indicator {
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

.online-dot {
  width: 8px;
  height: 8px;
  background-color: #22c55e;
  border-radius: 50%;
  display: inline-block;
}

/* Messages Area */
.chat-messages {
  flex: 1;
  overflow-y: auto;
  padding: 16px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  background-color: var(--white);
}

.message {
  max-width: 85%;
  padding: 12px 16px;
  border-radius: 16px;
  font-size: 0.9375rem;
  line-height: 1.5;
  animation: fadeIn 0.2s ease-out;
}

@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(8px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.message.received {
  align-self: flex-start;
  background-color: var(--gray-100);
  color: var(--gray-800);
  border-bottom-left-radius: 4px;
}

.message.sent {
  align-self: flex-end;
  background-color: var(--gray-800);
  color: var(--white);
  border-bottom-right-radius: 4px;
}

.message.system {
  align-self: center;
  background-color: transparent;
  color: var(--gray-500);
  font-size: 0.8125rem;
  padding: 8px 16px;
  max-width: 100%;
}

.message-meta {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 4px;
  font-size: 0.75rem;
}

.message.received .message-meta {
  color: var(--gray-500);
}

.message.sent .message-meta {
  color: var(--gray-300);
}

.message-user {
  font-weight: 500;
}

.message-time {
  opacity: 0.8;
}

.message-text {
  word-wrap: break-word;
}

/* Input Area */
.chat-input-area {
  position: sticky;
  bottom: 0;
  z-index: 10;
  padding: 12px 16px;
  background-color: var(--white);
  border-top: 1px solid var(--gray-200);
  flex-shrink: 0;
}

.chat-form {
  display: flex;
  gap: 12px;
  align-items: center;
}

.chat-input {
  flex: 1;
  padding: 12px 16px;
  border: 1px solid var(--gray-200);
  border-radius: 24px;
  font-size: 1rem;
  background-color: var(--gray-50);
  color: var(--gray-800);
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.chat-input:focus {
  outline: none;
  border-color: var(--gray-400);
  background-color: var(--white);
  box-shadow: var(--shadow-sm);
}

.chat-input::placeholder {
  color: var(--gray-400);
}

.send-button {
  width: 44px;
  height: 44px;
  border: none;
  border-radius: 50%;
  background-color: var(--gray-800);
  color: var(--white);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background-color 0.15s ease, transform 0.1s ease;
  flex-shrink: 0;
}

.send-button:hover {
  background-color: var(--gray-700);
}

.send-button:active {
  transform: scale(0.95);
}

.send-button:disabled {
  background-color: var(--gray-300);
  cursor: not-allowed;
}

/* Empty State */
.empty-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  height: 100%;
  color: var(--gray-400);
  text-align: center;
  padding: 20px;
}

.empty-state svg {
  width: 48px;
  height: 48px;
  margin-bottom: 12px;
  opacity: 0.5;
}

.empty-state p {
  font-size: 0.9375rem;
}

/* Safe area for iOS */
@supports (padding-bottom: env(safe-area-inset-bottom)) {
  .chat-input-area {
    padding-bottom: calc(12px + env(safe-area-inset-bottom));
  }
}

/* Desktop styles */
@media (min-width: 768px) {
  body {
    padding: 20px;
  }

  .chat-container {
    height: calc(100vh - 40px);
    border-radius: 12px;
    overflow: hidden;
    box-shadow: var(--shadow-md);
  }

  .chat-header {
    padding: 20px 24px;
  }

  .chat-messages {
    padding: 20px;
  }

  .chat-input-area {
    padding: 16px 20px;
  }

  .message {
    max-width: 70%;
  }
}