@charset "UTF-8";

body {
  background: #ccc;
  font-family: 'Courier New, sans-serif';
  font-weight: bold;
  font-size: 16px;
}

#container {
  width: 170px;
  margin: 0 auto;
  color: #fff;
}

#board {
  background: #fff;
  padding: 10px;
  border-radius: 8px;
  display: flex;
  flex-wrap: wrap;
}

.panel {
  cursor: pointer;
  background: #00aaff;
  width: 40px;
  height: 40px;
  margin: 5px;
  border-radius: 5px;
  box-shadow: 0 4px 0 #0088cc;
  line-height: 40px;
  text-align: center;
  position: relative;
}

.panel.hidden::after {
  content: '';
  cursor: pointer;
  background:lightgray;
  width: 40px;
  height: 40px;
  border-radius: 5px;
  box-shadow: 0 4px 0 lightgray;
  position: absolute;
  top: 0;
  left: 0;
}

.panel.flipped {
  background: lightgray;
  box-shadow: 0 4px 0 gray;
}

#btn {
  cursor: pointer;
  background: #f44336;
  box-shadow: 0 5px 0 #d1483e;
  padding: 7px;
  margin-top: 10px;
  border-radius: 5px;
  text-align: center;
}

#btn.restart {
  background: #24b168;
  box-shadow: 0 5px 0 #20995b;
}

#btn:hover {
  opacity: .8;
}

#btn:active {
  margin-top: 15px;
  box-shadow: none;
}

#score {
  text-align: right;
  margin: 10px 0;
  font-size: 24px;
}