body {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  width: 100vw;
  margin: 0;
  padding: 0;
  background: #111;
}
.container {
  display: grid;
  grid-template-columns: repeat(30, 1rem);
  grid-template-rows: repeat(30, 1rem);
  grid-gap: 0.2rem;
}
.square {
  height: 100%;
  width: 100%;

  background-color: #2f2f2f;
  box-shadow: 0 0 2px #000;
  transition: all 2s;
}
.square:hover {
  transition-duration: 0ms;
  background-color: var(--color);
  box-shadow: 0 0 2px var(--color), 0 0 10px var(--color);
}
/* 我发现根本不需要增加hover类 */