@import url('https://fonts.googleapis.com/css2?family=Funnel+Sans:ital,wght@0,300..800;1,300..800&display=swap');

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: "Funnel Sans", sans-serif;
  color: #002200;
  image-rendering: pixelated;
}

@keyframes background-move {
  from { background-position: 0px 0px; }
  to { background-position: 64px 112px; }
}

html {
  background-image: url('img/bg.png');
  font-size: 18px;

  animation: background-move 20s infinite linear;
}

main {
  display: block;
  width: 60rem;
  margin: 0 auto;
  padding: 1rem;
  min-height: 100vh;
  background-color: #b4e8b2;
  border: 2px solid #002200;
  text-align: center;
  position: relative;
}

.back {
  position: absolute;
  top: 1rem;
  left: 1rem;
}

div.grid {
  display: grid;
  width: 34rem;
  grid-template-columns: repeat(7, 4rem);
  grid-template-rows: repeat(7, 4rem);
  grid-gap: 1rem;
  margin: 0 auto;
}
div.grid div {
  border: 1px solid #000;
  border-radius: 0.5rem;
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;
  position: relative;
}
div.grid div.gray {
  background-color: #0000007f;
}
div.grid div.hollow {
  background-color: #00000040;
  color: #00000040;
}
div.grid div:not(.gray):not(.hollow) {
  background-color: #0f0;
  font-weight: bold;
  font-size: 2rem;
  cursor: pointer;
}
div.grid div:not(.gray):not(.hollow):nth-child(2n) {
  background-color: #f00;
}