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

:root {
  --bg: #f5f5f5;
  --text: #111;
  --btn-bg: #ffffff;
  --btn-text: #111;
  --btn-border: rgba(0,0,0,0.12);
  --btn-shadow: rgba(0,0,0,0.10);
  --btn-disabled: 0.65;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0b0b0c;
    --text: #f2f2f2;
    --btn-bg: #151518;
    --btn-text: #f2f2f2;
    --btn-border: rgba(255,255,255,0.14);
    --btn-shadow: rgba(0,0,0,0.35);
    --btn-disabled: 0.6;
  }
}

body {
  background: var(--bg);
  color: var(--text);
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
}

.wrap {
  height: 100vh;
  width: 100vw;

  display: flex;
  align-items: center;
  justify-content: center;

  padding: 16px;
  box-sizing: border-box;
}

.bigbtn {
  width: 100%;
  height: 100%;
  max-width: 900px;
  max-height: 900px;

  border: 1px solid var(--btn-border);
  border-radius: 22px;

  background: var(--btn-bg);
  color: var(--btn-text);

  box-shadow: 0 10px 30px var(--btn-shadow);

  font-size: clamp(28px, 6vw, 64px);
  font-weight: 800;
  letter-spacing: 0.2px;

  display: flex;
  align-items: center;
  justify-content: center;

  padding: 18px;
  text-align: center;

  -webkit-tap-highlight-color: transparent;
  user-select: none;
}

.bigbtn:active {
  transform: scale(0.99);
}

.bigbtn:disabled {
  opacity: var(--btn-disabled);
}