index.css

:root {
  color-scheme: light dark;
  font-size: 1.125rem;

  --text-color: #334259;
  --text-inverted-color: #fff;
  --text-muted-color: rgba(0, 0, 0, 0.5);
  --background-color: #fff;
  --button-background-color: #f0f0f0;
  --button-hover-background-color: #e0e0e0;
  --card-front-background-image: linear-gradient(120deg, #c471f5 0%, #fa71cd 100%);
  --card-back-background-image: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --table-row-border-color: #dee2e6;
}

@media (prefers-color-scheme: dark) {
  :root {
    --text-color: #fff;
    --text-inverted-color: #242828;
    --text-muted-color: rgba(255, 255, 255, 0.5);
    --background-color: #242828;
    --button-background-color: #343838;
    --button-hover-background-color: #444848;
    --card-front-background-image: linear-gradient(120deg, #f6d365 0%, #fda085 100%);
    --card-back-background-image: linear-gradient(120deg, #43e97b 0%, #38f9d7 100%);
    --table-row-border-color: #555;
  }
}

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

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

@media (min-width: 400px) {
  :root {
    font-size: 1.25rem;
  }
}

body {
  background-color: var(--background-color);
  color: var(--text-color);
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", "Liberation Sans", sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji";
  line-height: 1.5;
}

.button {
  align-items: center;
  background-color: var(--button-background-color);
  border: 1px solid transparent;
  border-radius: .25rem;
  box-shadow: none;
  color: var(--text-color);
  cursor: pointer;
  display: inline-flex;
  font-size: inherit;
  justify-content: flex-start;
  margin: 0;
  outline: 0;
  text-align: center;
  text-decoration: none;
  transition: color .15s ease-in-out, background-color .15s ease-in-out, border-color .15s ease-in-out, box-shadow .15s ease-in-out;
  user-select: none;
  vertical-align: middle;
}

.button:active,
.button:hover {
  background-color: var(--button-hover-background-color);
  color: var(--text-color);
}

.button {
  padding: .375rem .75rem;
}