:root {
  color-scheme: dark;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: #071016;
  color: #edf7ff;
}

* {
  box-sizing: border-box;
}

html,
body {
  width: 100%;
  min-height: 100%;
  margin: 0;
}

body {
  display: grid;
  place-items: center;
  min-height: 100vh;
  overflow: hidden;
  background:
    radial-gradient(circle at 20% 15%, rgba(0, 224, 255, 0.14), transparent 28%),
    radial-gradient(circle at 80% 20%, rgba(255, 64, 129, 0.12), transparent 24%),
    #071016;
}

.shell {
  position: relative;
  width: min(100vw, 980px);
  height: min(100vh, 720px);
  display: grid;
  place-items: center;
  padding: 20px;
}

canvas {
  width: 100%;
  height: 100%;
  max-width: 920px;
  max-height: 680px;
  border: 1px solid rgba(237, 247, 255, 0.2);
  background: #0b1620;
  box-shadow: 0 20px 70px rgba(0, 0, 0, 0.36);
}

.start-screen {
  position: absolute;
  inset: 20px;
  display: grid;
  place-items: center;
  background: rgba(7, 16, 22, 0.72);
  backdrop-filter: blur(8px);
}

.start-screen[hidden] {
  display: none;
}

.start-panel {
  width: min(90%, 420px);
  padding: 28px;
  border: 1px solid rgba(237, 247, 255, 0.18);
  border-radius: 8px;
  background: rgba(11, 22, 32, 0.86);
  text-align: center;
}

.eyebrow {
  margin: 0 0 8px;
  color: #00e0ff;
  font-size: 13px;
  font-weight: 700;
  text-transform: uppercase;
}

h1 {
  margin: 0 0 24px;
  font-size: 32px;
  line-height: 1.1;
}

.mode-buttons {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}

.mode-button {
  min-height: 48px;
  border: 1px solid rgba(237, 247, 255, 0.28);
  border-radius: 8px;
  background: rgba(237, 247, 255, 0.08);
  color: #edf7ff;
  font: inherit;
  font-weight: 700;
  cursor: pointer;
}

.mode-button:hover,
.mode-button:focus-visible {
  border-color: #00e0ff;
  outline: none;
}

.mode-button.primary {
  background: #00e0ff;
  color: #071016;
}

@media (max-width: 720px) {
  body {
    overflow: auto;
  }

  .shell {
    height: 100vh;
    padding: 10px;
  }

  .start-screen {
    inset: 10px;
  }

  .mode-buttons {
    grid-template-columns: 1fr;
  }
}