/* Structural grid boundaries and core application layout */
* { 
  box-sizing: border-box; 
  margin: 0; 
  padding: 0; 
  font-family: sans-serif; 
}
body { 
  display: flex; 
  height: 100vh; 
  background: #1e1e24; 
  color: #fff; 
}
.game { 
  flex: 2; 
  display: flex; 
  flex-direction: column; 
  align-items: center; 
  justify-content: center; 
  position: relative; 
  overflow: hidden; 
  background: #151518; 
}
.upgrades { 
  flex: 1; 
  background: #2c2c35; 
  border-left: 4px solid #444; 
  padding: 20px; 
  overflow-y: auto; 
  display: flex; 
  flex-direction: column; 
  gap: 15px; 
}
#upgrades-container {
  display: flex; 
  flex-direction: column; 
  gap: 12px;
}
.sidebar-title { 
  font-size: 1.5rem; 
  color: #fff; 
  border-bottom: 2px solid #444; 
  padding-bottom: 10px; 
}