body {
  height: 90vmin;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
}

.sqr-row {
  display: flex;
}

.sqr,.edge {
  display: flex;
  justify-content: center;
  align-items: center;
  width: 25px;
  height: 25px;
  border: 1px solid black;
}

button {
  margin: 10px;
}