stylesheet.css

:root {
  --number-of-squares: 16;
  --background-color: white;
}

body {
  background-color: #c0d7bb;
}

h3 {
  color: black;
}

.controls {
  width: 100%;
  margin: auto;
  margin-top: -10px;
  margin-bottom: 10px;
  text-align: center;
}

.controls input{
  text-align: center;
  width: 150px;
}

.controls button {
 background-color: #85bda6;
 color: black;
 border-radius: 4px;
 border-width: 1px;
 border: solid #85bda6;
 padding: 5px;
 margin-top: 5px;
}

#board {
  border: black solid;
  width: 75vh;
  height: 75vh;
  display: grid;
  grid-template-columns: repeat(var(--number-of-squares), 1fr);
  grid-template-rows: repeat(var(--number-of-squares), 1fr);
  margin: auto;
}

.grid {
  background: #a9fff7;
}

@keyframes fade-in {
  from {opacity: 0;}
  to   {opacity: 1;}
}

.selected {
  animation: fade-in .5s;
  background-color: #3e885b;
}