* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
  width: 100%;
  height: 100%;
}

body {
  font-family: sans-serif;
  font-size: 1em;
  line-height: 1;
  letter-spacing: 0.2px;
}

h1,
h2,
h3,
h4,
h5 {
  letter-spacing: 0.4px;
}

a {
  text-decoration: none;
  color: dodgerblue;
}

a:hover {
  text-decoration: none;
  color: deepskyblue;
}

template {
  display: none;
}

main {
  display: flex;
  width: 100%;
  height: 100%;
}

.container {
  margin: 0 auto;
  max-width: 720px;
}

.header {
  height: 60px;
}

.grid {
  display: flex;
  flex-wrap: wrap;
  flex-direction: row;
}

.cell {
  display: inline-block;
  width: 40px;
  height: 40px;
  border: 2px solid #302021;
  text-align: center;
  line-height: 37px;
  font-weight: bold;
  cursor: pointer;
  font-family: sans-serif;
  font-size: 20px;
  cursor: pointer;
  margin: 4px;
}

.active {
  background-color: orange;
}