* { margin: 0; padding: 0; box-sizing: border-box; -webkit-tap-highlight-color: transparent; user-select: none; }
html, body {
  width: 100%; height: 100vh; overflow: hidden;
  font-family: 'Apple SD Gothic Neo', -apple-system, sans-serif;
  touch-action: none;
  background: #fff8e7;
}
.back-btn {
  position: fixed;
  top: max(12px, env(safe-area-inset-top));
  left: max(12px, env(safe-area-inset-left));
  width: 52px; height: 52px;
  border-radius: 50%;
  background: rgba(255,255,255,0.85);
  border: 3px solid #ff8fb1;
  display: flex; align-items: center; justify-content: center;
  font-size: 26px;
  text-decoration: none;
  color: #ff5e87;
  z-index: 1000;
  box-shadow: 0 4px 12px rgba(0,0,0,0.15);
  cursor: pointer;
}
.back-btn:active { transform: scale(0.9); }