*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html, body {
  width: 100%; height: 100%;
  background: #0d1117;
  display: flex; justify-content: center; align-items: center;
  font-family: sans-serif;
  overflow: hidden;
}
#wrap { position: relative; }
#menuBtn {
  position: absolute;
  top: 10px; right: 10px;
  padding: 6px 14px;
  background: rgba(20,20,40,0.82);
  color: rgba(255,255,255,0.75);
  border: 1px solid rgba(255,255,255,0.18);
  border-radius: 6px;
  font: bold 12px sans-serif;
  letter-spacing: 1px;
  cursor: pointer;
  display: none;
  transition: background 0.15s, color 0.15s;
}
#menuBtn:hover {
  background: rgba(40,40,80,0.95);
  color: #fff;
}
#c {
  display: block;
  border: 2px solid rgba(255,255,255,0.08);
  border-radius: 6px;
  box-shadow: 0 8px 40px rgba(0,0,0,0.7);
}