:root {
  --ink: #16202a;
  --muted: #56606b;
  --accent: #0b6bcb;
  --warn: #8a4b00;
  --bg: #f6f7f8;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font: 18px/1.45 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}

main {
  max-width: 560px;
  margin: 0 auto;
  padding: 20px 16px 32px;
}

h1 { font-size: 22px; margin: 0 0 20px; }
.big { font-size: 20px; font-weight: 600; }
.small { color: var(--muted); font-size: 15px; }
.warn { color: var(--warn); font-weight: 600; }

button {
  display: block;
  width: 100%;
  min-height: 64px;
  margin: 12px 0;
  border: 2px solid var(--accent);
  border-radius: 14px;
  background: #fff;
  color: var(--accent);
  font: inherit;
  font-size: 20px;
  font-weight: 600;
}

button.primary { background: var(--accent); color: #fff; }
button:active { transform: translateY(1px); }

progress { width: 100%; height: 18px; }

#stage {
  position: relative;
  margin-top: 12px;
}

/* A visible frame is required: mobile browsers throttle hidden or offscreen iframes. */
#stage iframe {
  display: block;
  width: 100%;
  height: 55vh;
  border: 1px solid #cfd4d9;
  border-radius: 8px;
  background: #fff;
}

/* Taps must not reach the test page. */
#stage::after {
  content: "";
  position: absolute;
  inset: 0;
}