main.css

:root {
  --font-size: 2.0rem;
  --font-size--mobile: 1.6rem;
  --line-height: 1.08;

  --margin: 6rem;
  /*originally 3.2rem*/
  --margin--mobile: 1.6rem;

  --columns: 4;
  --columns--mobile: 2;

  --font-family: Arial, sans-serif;
}

*,
*:after,
*:before {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  font-size: 62.5%; /* Now 10px = 1rem! */
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-family);
  font-size: var(--font-size);
  line-height: var(--line-height);

  min-height: 100vh;
  background-image: url("./images/background/Car.png");
  background-attachment: fixed;
  background-repeat: no-repeat;
  background-position: center center;
  background-size: cover;
}

ul {
  list-style-type: none;
}

.images__list {
  display: flex;
  flex-wrap: wrap;
}

.images__list__item {
  width: calc(100vw / var(--columns));
  height: calc(100vw / var(--columns));
  padding: var(--margin);
}

.images__list__item img {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: contain;
  object-position: center center;
}

.tooltip {
  display: none;
  position: fixed;
  top: 0;
  left: 0;

  background: #fff;
  color: #000;
  padding: calc(0.25 * var(--margin));
}

.tooltip.active {
  display: block;
}

@media screen and (max-width: 768px) {
  :root {
    --margin: var(--margin--mobile);
    --font-size: var(--font-size--mobile);
    --columns: var(--columns--mobile);
  }
}