body {
  font-family: Arial, sans-serif;
  margin: 0;
  padding: 0;
  text-align: center;
}

#upgradeUi {
  position: fixed; 
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  z-index: 999; /* 다른 UI 위로 오게 1*/
  background: #fff;
  padding: 20px;
  border-radius: 10px;
}

header {
  background: #333;
  color: white;
  padding: 13px;
  position: relative;
  height: 120px;
}

header h1 {
  margin: 0.4em 0;
}

header img {
  position: absolute;
  left: 5%;
  top: 50%;
  transform: translateY(-50%);
}

nav {
  margin-top: 10px;
}

nav button {
  padding: 10px 20px;
  margin: 5px;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  background: none;
  color: white;
  font-size: 16px;
}
nav button:hover {
  background: #45a049;
}

main {
  padding: 20px;
}

/* 탭 콘텐츠 기본 숨김 */
.tab-content {
  display: none;
}
.tab-content.active {
  display: block;
  animation: fadeIn 0.4s ease;
}

/* 광고 박스 */
.adsbygoogle {
  margin: 20px auto;
}

/* 애니메이션 */
@keyframes fadeIn {
  from { opacity: 0; }
  to   { opacity: 1; }
}

/* 모바일 대응 */
@media (max-width: 768px) {
  #board-canvas {
    width: 95vw;
    height: 95vw;
  }
}