* { 
  box-sizing: border-box; 
  margin: 0; 
  padding: 0; 
  font-family: 'Segoe UI', -apple-system, BlinkMacSystemFont, sans-serif; 
}

body { 
  display: flex; 
  height: 100vh; 
  background-color: #f0f2f5; 
  color: #3b4a44; 
}

#app { 
  display: flex; 
  width: 100%; 
  height: 100%; 
}

#auth-screen { 
  display: flex; 
  flex-direction: column; 
  align-items: center; 
  justify-content: center; 
  width: 100%; 
  height: 100%; 
  background: #00a884; 
  color: white; 
}

#chat-screen { 
  display: none; 
  width: 100%; 
  height: 100%; 
}

.auth-box { 
  background: white; 
  padding: 30px; 
  border-radius: 8px; 
  width: 90%; 
  max-width: 400px; 
  box-shadow: 0 4px 10px rgba(0,0,0,0.1); 
  text-align: center; 
}

.auth-box h2 {
  color: #3b4a44;
  margin-bottom: 10px;
}

.auth-box input { 
  width: 100%; 
  padding: 12px; 
  margin: 15px 0; 
  border: 1px solid #e9edef; 
  border-radius: 4px; 
  font-size: 16px; 
  color: #3b4a44;
}

.auth-box button { 
  width: 100%; 
  padding: 12px; 
  background: #00a884; 
  border: none; 
  color: white; 
  font-weight: bold; 
  cursor: pointer; 
  border-radius: 4px; 
  transition: background 0.2s; 
}

.auth-box button:hover { 
  background: #008069; 
}

#sidebar { 
  width: 30%; 
  border-right: 1px solid #e9edef; 
  background: white; 
  display: flex; 
  flex-direction: column; 
}

#sidebar-header { 
  padding: 15px; 
  background: #f0f2f5; 
  font-weight: bold; 
  color: #008069; 
}

#contact-selector { 
  padding: 10px; 
  display: flex; 
  gap: 5px; 
  border-bottom: 1px solid #e9edef; 
}

#contact-selector input { 
  flex: 1; 
  padding: 8px; 
  border: 1px solid #e9edef; 
  border-radius: 4px; 
}

#contact-selector button { 
  padding: 8px; 
  background: #00a884; 
  color: white; 
  border: none; 
  border-radius: 4px; 
  cursor: pointer; 
}

#chat-list { 
  flex: 1; 
  overflow-y: auto; 
}

.chat-item { 
  padding: 15px; 
  border-bottom: 1px solid #f0f2f5; 
  cursor: pointer; 
  transition: background 0.1s; 
}

.chat-item:hover { 
  background: #f0f2f5; 
}

#main-chat { 
  width: 70%; 
  display: flex; 
  flex-direction: column; 
  background: #efeae2; 
}

#chat-header { 
  padding: 15px; 
  background: #f0f2f5; 
  border-bottom: 1px solid #e9edef; 
  font-weight: bold; 
}

#message-container { 
  flex: 1; 
  padding: 20px; 
  overflow-y: auto; 
  display: flex; 
  flex-direction: column; 
  gap: 10px; 
}

.message { 
  max-width: 60%; 
  padding: 10px; 
  border-radius: 8px; 
  font-size: 14px; 
  word-wrap: break-word; 
}

.message.sent { 
  background: #d9fdd3; 
  align-self: flex-end; 
}

.message.received { 
  background: white; 
  align-self: flex-start; 
}

#input-area { 
  padding: 10px; 
  background: #f0f2f5; 
  display: flex; 
}

#input-area input { 
  flex: 1; 
  padding: 12px; 
  border: none; 
  border-radius: 8px; 
  font-size: 15px; 
}