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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background: #f0f2f5;
  min-height: 100vh;
  padding: 24px 16px;
}

.container {
  max-width: 640px;
  margin: 0 auto;
}

h1 {
  font-size: 1.5rem;
  font-weight: 700;
  color: #1a1a2e;
  margin-bottom: 20px;
}

.compose {
  display: flex;
  gap: 8px;
  margin-bottom: 24px;
}

#message-input {
  flex: 1;
  padding: 10px 14px;
  border: 1px solid #d1d5db;
  border-radius: 8px;
  font-size: 1rem;
  outline: none;
  background: #fff;
  transition: border-color 0.15s;
}

#message-input:focus {
  border-color: #6366f1;
}

#send-btn {
  padding: 10px 20px;
  background: #6366f1;
  color: #fff;
  border: none;
  border-radius: 8px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s;
}

#send-btn:hover {
  background: #4f46e5;
}

#send-btn:disabled {
  background: #a5b4fc;
  cursor: not-allowed;
}

#messages {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.message {
  background: #fff;
  border: 1px solid #e5e7eb;
  border-radius: 10px;
  padding: 14px 16px;
}

.message-text {
  color: #111827;
  font-size: 1rem;
  word-break: break-word;
}

.message-time {
  margin-top: 6px;
  font-size: 0.75rem;
  color: #9ca3af;
}

.empty {
  text-align: center;
  color: #9ca3af;
  font-size: 0.95rem;
  padding: 40px 0;
}