*, *:after, *:before {
  box-sizing: border-box;
}

:root {
  --dark: #53565a;
  --light: #a7a8aa;
  --highlight: #ffd100;
  --background: #7BA7BC;
  --transition: transform .15s;
  --ratio: 4;
  --maxBoardWidth: 80vmin;
}
@media (min-width: 480px) {
  :root {
    --maxBoardWidth: 55vmin;
  }
}

body {
  font-family: Nunito, sans-serif;
  min-height: 100vh;
  margin: 0;
  display: grid;
  place-items: center;
  color: var(--dark);
  background-color: var(--background);
  background: linear-gradient(-20deg, var(--highlight), var(--background) 60%);
}

form, button, input {
  font-family: Nunito, sans-serif;
  color: var(--dark);
  cursor: pointer;
}

#board {
  text-align: center;
  display: grid;
  place-items: center;
  position: relative;
  width: 100%;
}
#board #game-board {
  width: var(--maxBoardWidth);
  height: var(--maxBoardWidth);
  border-radius: 6px;
  border: 1.5vmin solid var(--dark);
  background: var(--dark);
  color: var(--dark);
  cursor: pointer;
  display: flex;
  justify-content: center;
  position: relative;
  overflow: hidden;
}
#board #game-board + p {
  margin: 1em 0 0;
}
#board > p {
  font-size: 1.4rem;
}
#board #options {
  width: var(--maxBoardWidth);
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
}
#board #options .options-group {
  width: 100%;
  padding-top: 1em;
  margin: 1em 0 0;
  border-top: 1px solid;
}
#board #options .options-group input {
  transform: scale(1.5);
  margin-right: 0.5em;
}
#board #options .options-group label {
  vertical-align: middle;
}
#board #options button {
  margin: 1em 0;
  padding: 2vmin 3vmin;
  font-size: 1rem;
  border-radius: 1vmin;
  border: 0.5vmin solid var(--light);
  text-transform: uppercase;
  outline-color: var(--highlight);
}

#innerBoard {
  display: grid;
  height: 100%;
  width: 100%;
  margin: 0 auto;
  overflow: hidden;
}
#innerBoard .square {
  cursor: initial;
  padding: 0;
  font-size: calc(4.2vmin - (var(--ratio) * .1vmin));
  display: grid;
  text-align: center;
  place-items: center;
  border: none;
  background: #fff;
  position: relative;
  z-index: 1;
}
@media (min-width: 480px) {
  #innerBoard .square {
    font-size: calc(4vmin - (var(--ratio) * .2vmin));
  }
}
#innerBoard .square span {
  transition: transform 0.1s;
  pointer-events: none !important;
}
#innerBoard .square:focus {
  outline: none;
}
#innerBoard .square:focus span {
  transform: scale(1.5);
}
#innerBoard .square.possible-move {
  cursor: pointer;
  background: #f1f6f8;
}
#innerBoard .square.possible-move:hover span {
  transform: scale(1.3);
}
#innerBoard .square.correct {
  color: var(--highlight) !important;
}
#innerBoard .square:empty {
  background: var(--dark);
  border-color: var(--dark);
  border: none;
  z-index: 0;
}
#innerBoard .square:empty:focus {
  outline: none;
  border-radius: 8px;
  outline-offset: -1vmin;
  -webkit-animation: swell 0.7s infinite alternate ease-in-out;
          animation: swell 0.7s infinite alternate ease-in-out;
}
#innerBoard .square:empty:focus:before {
  width: 50%;
  height: 50%;
  content: "";
  background-color: var(--highlight);
  position: absolute;
  top: calc(50% - 25%);
  left: calc(50% - 25%);
  transform: rotate(45deg);
}
#innerBoard .square:empty:focus:after {
  content: "";
  width: 45%;
  height: 45%;
  background-color: var(--dark);
  position: absolute;
  top: calc(50% - 22.5%);
  left: calc(50% - 22.5%);
  z-index: 3;
}

.loader {
  display: flex;
  align-items: center;
  position: absolute;
  text-align: left;
  top: -0.5em;
  left: -0.5em;
  width: calc(100% + 1em);
  height: calc(100% + 1em);
  color: #fff;
  background: var(--dark);
  opacity: 0.9;
  z-index: 10;
  text-transform: uppercase;
}
.loader p {
  font-size: calc(.6em + 4vmin);
  padding: 0 1.5em;
}

.fade-enter-active,
.fade-leave-active {
  transition: all 0.2s;
}

.fade-enter,
.fade-leave-to {
  opacity: 0;
  transform: translateY(0.5em);
}

.dot {
  animation: pulse 0.6s infinite reverse;
  -webkit-animation-delay: 0;
          animation-delay: 0;
}
.dot + .dot {
  -webkit-animation-delay: 0.2s;
          animation-delay: 0.2s;
}
.dot:last-of-type {
  -webkit-animation-delay: 0.4s;
          animation-delay: 0.4s;
}

.slide-move {
  transition: var(--transition);
  filter: blur(0.3vmin);
}

@-webkit-keyframes swell {
  0% {
    transform: scale(1);
  }
  100% {
    transform: scale(1.15);
  }
}

@keyframes swell {
  0% {
    transform: scale(1);
  }
  100% {
    transform: scale(1.15);
  }
}
@-webkit-keyframes pulse {
  0% {
    opacity: 0;
  }
  100% {
    opacity: 1;
  }
}
@keyframes pulse {
  0% {
    opacity: 0;
  }
  100% {
    opacity: 1;
  }
}