style.css

html {
  box-sizing: border-box;
  height: 100%;
}

*,
*:before,
*:after {
  box-sizing: inherit;
}

:root {
  --bg-color: #111;
  --text-color: #eee;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg-color: #111;
    --text-color: #eee;
  }
}

body {
  margin: 0;
  height: 100%;
  background-color: var(--bg-color);
  color: var(--text-color);
  font-family: -apple-system, system-ui, sans-serif;
  font-variant: tabular-nums;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  font-size:5vmin;
}

#title {
  font-size:15vmin;
}

.progress-bar-container {
  width: 90%;
  height: 25%;
  min-height: 40px;
  max-height: 60px;
  box-shadow: 0 0 0 2px var(--text-color);
  border: 2px solid var(--bg-color);
  border-radius: 10px;
  overflow: hidden;
}

#progress-bar {
  height: 100%;
  width: 0; /* gets updated via JS */
  background-color: var(--text-color);
}