:root {
  --bg: #f1f1f1;
  --card: white;
  --self: #cdeaff;
  --text: black;
}
[data-theme="dark"] {
  --bg: #121212;
  --card: #1f1f1f;
  --self: #2b8cbf;
  --text: #f1f1f1;
}
body {
  font-family: Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  margin: 0;
  padding: 0;
}
.chat-container {
  max-width: 600px;
  margin: 50px auto;
  background: var(--card);
  border-radius: 10px;
  overflow: hidden;
  box-shadow: 0 0 10px rgba(0,0,0,0.1);
  display: flex;
  flex-direction: column;
  height: 80vh;
}
.chat-header {
  padding: 10px;
  background: #007bff;
  color: white;
  text-align: center;
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.chat-box {
  flex: 1;
  padding: 10px;
  overflow-y: auto;
}
.chat-message {
  margin-bottom: 10px;
  padding: 8px;
  background: #e0e0e0;
  border-radius: 5px;
}
.chat-message.self {
  background: var(--self);
  text-align: right;
}
.chat-input {
  display: flex;
  border-top: 1px solid #ccc;
}
.chat-input input {
  flex: 1;
  padding: 10px;
  border: none;
  font-size: 16px;
}
.chat-input button {
  padding: 10px;
  background: #007bff;
  color: white;
  border: none;
  cursor: pointer;
}
.chat-input button:hover {
  background: #0056b3;
}
.username-modal {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.5);
  display: flex;
  align-items: center;
  justify-content: center;
}
.username-modal input {
  padding: 10px;
  font-size: 16px;
}
.username-modal button {
  margin-left: 10px;
  padding: 10px;
}