* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
  width: 100%;
  height: 100%;
  background: radial-gradient(circle at 50% 20%, #2b3e5d, #0b1222 70%);
  color: #e8eef7;
  font-family: "Inter", "Segoe UI", sans-serif;
}

#game-shell {
  position: relative;
  width: 100%;
  height: 100%;
  overflow: hidden;
}

#game-container {
  position: absolute;
  inset: 0;
  z-index: 1;
}

#game-container canvas {
  display: block;
  width: 100vw;
  height: 100vh;
}

.panel {
  position: absolute;
  backdrop-filter: blur(6px);
  background: rgba(8, 15, 28, 0.55);
  border: 1px solid rgba(255, 255, 255, 0.18);
  border-radius: 14px;
  box-shadow: 0 10px 28px rgba(0, 0, 0, 0.28);
}

#hud {
  top: 14px;
  left: 14px;
  z-index: 20;
  display: grid;
  grid-template-columns: repeat(2, minmax(140px, 1fr));
  gap: 10px 14px;
  padding: 12px 14px;
  min-width: 300px;
}

.stat {
  display: flex;
  flex-direction: column;
  gap: 3px;
}

.stat span {
  font-size: 0.75rem;
  opacity: 0.8;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.stat strong {
  font-size: 1rem;
  font-weight: 600;
}

.center-panel {
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
  width: min(92vw, 440px);
  padding: 18px 20px;
  text-align: center;
  z-index: 30;
}

.center-panel h1,
.center-panel h2 {
  margin: 0 0 8px;
  font-weight: 700;
  letter-spacing: 0.02em;
}

.center-panel p {
  margin: 6px 0 14px;
  line-height: 1.45;
  opacity: 0.9;
}

button {
  border: none;
  border-radius: 10px;
  background: linear-gradient(180deg, #5fa5ff, #3d6fd4);
  color: #f6fbff;
  padding: 10px 14px;
  font-weight: 600;
  cursor: pointer;
  transition: transform 120ms ease, filter 120ms ease;
}

button:hover {
  transform: translateY(-1px);
  filter: brightness(1.05);
}

button:disabled {
  opacity: 0.45;
  cursor: default;
  transform: none;
}

.upgrade-list {
  margin: 8px 0 12px;
  display: grid;
  grid-template-columns: 1fr;
  gap: 8px;
}

.upgrade-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 8px 10px;
  border-radius: 10px;
  background: rgba(255, 255, 255, 0.06);
  text-align: left;
  gap: 8px;
}

.upgrade-label {
  font-size: 0.9rem;
}

.hidden {
  display: none;
}

@media (max-width: 700px) {
  #hud {
    min-width: unset;
    width: calc(100vw - 28px);
    grid-template-columns: repeat(2, minmax(110px, 1fr));
  }
}