style.css

:root {
  --background-color: #333;
  --text-color: #ccc;
  --text-color-light: #fff;
  --text-color-dark: #aaa;
}

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

body {
  background-color: var(--background-color);
  display: flex;
  flex-direction: column;
  width: min-content;
  height: 100vh;
  margin: 0 auto;
  font-size: 7.5vmin;
}

.header {
  display: flex;
  padding-bottom: 1vmin;
  margin-top: 2.5vmin;
  border-bottom: 1px solid var(--text-color);
  align-items: center;
  gap: 1vmin;
  color: var(--text-color);
}

.restart {
  all: unset;
  border-radius: 3px;
  padding: 8px;
  background-color: var(--text-color-dark);
  font-size: max(1vmin, 20px);
  color: white;
  cursor: pointer;
}

.title {
  text-align: center;
  margin: 0;
  font-size: max(5vmin, 20px);
  flex-grow: 1;
}

.stat-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: flex-end;
}

.stat-label {
  position: relative;
  font-size: max(2vmin, 10px);
  color: var(--text-color-dark);
  text-align: center;
  line-height: 1.2;
}

.score-container {
  flex-basis: calc(max(10vmin, 70px) + 1vmin);
  flex-shrink: 0;
}

.score-amount {
  animation: show 100ms ease-in-out;
}

.stat-amount {
  font-size: max(3vmin, 15px);
  font-weight: bold;
  text-align: center;
}

.game-board {
  margin: auto 0;
  display: grid;
  grid-template-columns: repeat(var(--grid-size), var(--cell-size));
  grid-template-rows: repeat(var(--grid-size), var(--cell-size));
  background-color: #ccc;
  border-radius: 1vmin;
  gap: var(--cell-gap);
  padding: var(--cell-gap);
  position: relative;
}

.cell {
  background-color: var(--text-color-dark);
  border-radius: 1vmin;
}

.tile {
  /* --x: 2;
  --y: 3;
  --background-lightness: 80%;
  --text-lightness: 20%; */
  position: absolute;
  display: flex;
  justify-content: center;
  align-items: center;
  width: var(--cell-size);
  height: var(--cell-size);
  border-radius: 1vmin;
  top: calc(var(--y) * (var(--cell-size) + var(--cell-gap)) + var(--cell-gap));
  left: calc(var(--x) * (var(--cell-size) + var(--cell-gap)) + var(--cell-gap));
  font-weight: bold;
  background-color: hsl(200, 50%, var(--background-lightness));
  color: hsl(200, 25%, var(--text-lightness));
  /* Use when the tile appears */
  animation: show 200ms ease-in-out;
  /* Use when the tile moves */
  transition: 100ms ease-in-out;
}

@keyframes show {
  0% {
    opacity: 0.5;
    transform: scale(0);
  }
}