* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
body {
  font-family: "Segoe UI", Tahoma, sans-serif;
  background: linear-gradient(135deg, #667eea, #764ba2);
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}
.chat-container {
  width: 90%;
  max-width: 500px;
  height: 600px;
  background: white;
  border-radius: 20px;
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
  display: flex;
  flex-direction: column;
  overflow: hidden;
}
.chat-header {
  background: linear-gradient(135deg, #667eea, #764ba2);
  color: white;
  padding: 15px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.chat-header .title {
  font-size: 20px;
  font-weight: bold;
}
.online-users {
  font-size: 12px;
  opacity: 0.9;
}
.chat-messages {
  flex: 1;
  padding: 20px;
  overflow-y: auto;
  background: #f5f5f5;
}
.message {
  margin-bottom: 15px;
  display: flex;
  align-items: flex-end;
  animation: slideIn 0.3s ease;
}
@keyframes slideIn {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}
.message-bubble {
  max-width: 70%;
  padding: 10px 14px;
  border-radius: 18px;
  word-wrap: break-word;
}
.message .username {
  font-weight: bold;
  font-size: 12px;
  margin-bottom: 5px;
  display: block;
}
.sent {
  justify-content: flex-end;
}
.received {
  justify-content: flex-start;
}
.sent .message-bubble {
  background: linear-gradient(135deg, #667eea, #764ba2);
  color: white;
  border-bottom-right-radius: 4px;
}
.received .message-bubble {
  background: white;
  color: #333;
  border-bottom-left-radius: 4px;
  box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}
.message-time {
  font-size: 10px;
  margin-top: 3px;
  opacity: 0.7;
  text-align: right;
}
.avatar {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  margin: 0 8px;
  object-fit: cover;
}
.chat-input-area {
  padding: 15px;
  background: white;
  border-top: 1px solid #ddd;
  display: flex;
  gap: 10px;
}
.chat-input {
  flex: 1;
  padding: 12px 16px;
  border: 2px solid #eee;
  border-radius: 25px;
  font-size: 14px;
  outline: none;
  transition: border-color 0.3s;
}
.chat-input:focus {
  border-color: #667eea;
}
.send-button {
  padding: 12px 24px;
  background: linear-gradient(135deg, #667eea, #764ba2);
  color: white;
  border: none;
  border-radius: 25px;
  cursor: pointer;
  font-weight: bold;
  transition: transform 0.2s, box-shadow 0.2s;
}
.send-button:hover {
  transform: translateY(-2px);
  box-shadow: 0 5px 15px rgba(102, 126, 234, 0.4);
}
.username-setup {
  text-align: center;
  padding: 20px;
  background: white;
  border-radius: 15px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
}
.username-setup input {
  width: 80%;
  padding: 10px;
  border-radius: 10px;
  border: 2px solid #ccc;
  margin-bottom: 10px;
}
.username-setup button {
  background: linear-gradient(135deg, #667eea, #764ba2);
  color: white;
  border: none;
  padding: 10px 20px;
  border-radius: 10px;
  cursor: pointer;
}