* { box-sizing: border-box; }
html, body {
  margin: 0;
  width: 100%;
  height: 100%;
  overflow: hidden;
  background: #07111d;
  font-family: Arial, Helvetica, sans-serif;
}
body {
  display: flex;
  align-items: center;
  justify-content: center;
}
#game-shell {
  position: relative;
  width: 100%;
  height: 100%;
  max-width: 100%;
  max-height: 100%;
  overflow: hidden;
  background: linear-gradient(180deg, #081322 0%, #050c16 100%);
}
#gameCanvas {
  display: block;
  width: 100%;
  height: 100%;
  background: #17202e;
}
.overlay {
  position: absolute;
  inset: 0;
  display: none;
  align-items: center;
  justify-content: center;
  background: rgba(3, 8, 16, 0.58);
  backdrop-filter: blur(3px);
  padding: 16px;
}
.overlay.visible { display: flex; }
.overlay-card {
  width: min(92%, 360px);
  text-align: center;
  color: #eef7ff;
  background: rgba(8, 18, 32, 0.94);
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: 20px;
  padding: 24px 20px;
  box-shadow: 0 15px 40px rgba(0,0,0,0.35);
}
.overlay-card h1,
.overlay-card h2 {
  margin: 0 0 12px;
}
.overlay-card p {
  margin: 0 0 14px;
  line-height: 1.5;
  color: #d8e8ff;
}
.overlay-card .small {
  font-size: 14px;
  color: #99b3d4;
}
.ui-btn {
  border: 0;
  border-radius: 14px;
  padding: 12px 18px;
  min-width: 150px;
  font-size: 16px;
  font-weight: 700;
  cursor: pointer;
  color: #03101a;
  background: linear-gradient(135deg, #35d7ff, #00a8ff);
}