html,
body {
  margin: 0;
  height: 100%;
  background: #eaf2f8;
  color: #102a43;
  font-family: "IBM Plex Sans", "Segoe UI", sans-serif;
}

.app {
  min-height: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 12px;
  padding: 16px;
  box-sizing: border-box;
}

.app h1 {
  margin: 0;
  letter-spacing: 0.04em;
  font-size: 1.35rem;
}

.frame {
  position: relative;
  border: 2px solid #486581;
  box-shadow: 0 10px 20px rgba(16, 42, 67, 0.2);
  background: #0b1f31;
}

canvas {
  display: block;
  width: min(96vw, 960px);
  height: calc(min(96vw, 960px) * 0.5625);
  max-height: 84vh;
}

.overlay {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  gap: 8px;
  background: rgba(3, 28, 47, 0.76);
  color: #d9f2ff;
  padding: 18px;
}

#start-btn {
  border: 0;
  padding: 10px 18px;
  border-radius: 6px;
  font-size: 0.95rem;
  background: #17bebb;
  color: #072a40;
  font-weight: 700;
  cursor: pointer;
}

#start-btn:hover {
  background: #29d6d2;
}