* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  font-family: 'Segoe UI', 'Helvetica Neue', Arial, sans-serif;
  background: #fff;
  color: #000;
  position: relative;
}

.hint-btn {
  position: fixed;
  top: 20px;
  right: 20px;
  background: rgba(0, 0, 0, 0.05);
  border: 1px solid rgba(0, 0, 0, 0.2);
  color: #000;
  padding: 8px 18px;
  border-radius: 6px;
  cursor: pointer;
  font-size: 14px;
  text-decoration: none;
  transition: background 0.2s;
  z-index: 1000;
}

.hint-btn:hover {
  background: rgba(0, 0, 0, 0.12);
}

.levelup-overlay {
  display: none;
  position: fixed;
  top: 0; left: 0; right: 0; bottom: 0;
  background: rgba(255,255,255,0.95);
  z-index: 9999;
  align-items: center;
  justify-content: center;
}
.levelup-overlay.show {
  display: flex;
}
.levelup-text {
  font-size: 36px;
  font-weight: 900;
  color: #000;
  animation: levelup-pop 0.3s ease-out;
}
@keyframes levelup-pop {
  0% { transform: scale(0.5); opacity: 0; }
  100% { transform: scale(1); opacity: 1; }
}
body.dark .levelup-overlay {
  background: rgba(0,0,0,0.95);
}
body.dark .levelup-text {
  color: #fff;
}

.container {
  text-align: center;
  padding: 20px;
  width: 100%;
  max-width: 800px;
}