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

button:hover,
a:hover {
  cursor: pointer;
}

.clearfix::after {
  content: "";
  display: block;
  clear: both;
}

html {
  min-height: 100%;
  width: 100%;
  font-size: 16px;
  font-family: "Rubik", sans-serif;
  line-height: 1.5em;
  color: #776e65;
  background: #faf8ef;
}

.wrapper {
  max-width: 500px;
  margin: 0 auto;
  padding: 15px;
}

h2 {
  font-style: italic;
}

/* Introduction */
.intro {
  margin-bottom: 60px;
}
.intro_title {
  text-align: center;
  color: #776e65;
  font-size: 3rem;
}

@media (max-width: 768px) {
  .intro {
    display: none;
  }
}

/**/
/* Guide instructions */
.guide {
  border-bottom: 1px solid grey;
}
.guide:first-of-type {
  margin-top: 4rem;
  border-top: 1px solid gray;
}
.guide_arrow {
  display: inline-block;
  margin: 15px;
  font-size: 3rem;
  color: #fff;
}

.controls_game, .controls_score {
  display: inline-block;
  width: 50%;
  float: left;
}
@media all and (max-width: 767px) {
  .controls_game, .controls_score {
    width: 100%;
  }
}
.controls_game-btn {
  margin-bottom: 1rem;
  padding: 0.5em 0.75em;
  background: #8f7a66;
  color: #f9f6f2;
  -webkit-appearance: none;
     -moz-appearance: none;
          appearance: none;
  border: none;
  border-radius: 3px;
  box-shadow: none;
  letter-spacing: 0.05em;
  font-weight: bold;
  text-transform: none;
}
.controls_game-btn:hover {
  background: #9f8b76;
}
.controls_score {
  display: inline-block;
  min-width: 4em;
  margin-bottom: 4rem;
  padding: 0.5em 0.75em;
  text-align: center;
  background: #bbada0;
  border-radius: 3px;
}
.controls_score-label, .controls_score-text {
  display: inline-block;
}
.controls_score-label {
  color: #f9f6f2;
}
.controls_score-text {
  color: #f9f6f2;
  font-size: 2rem;
}

/**/
/*
  Gameboard:
  the container for the static grid background; and generated tiles/numbers;
*/
.gameboard {
  /* Position: relative; set for tile-container, which absolutely positions over it to match grid's dimensions; */
  position: relative;
  width: 100%;
  max-width: 500px;
  height: 100%;
  max-height: 500px;
  margin: auto;
  padding: 8px;
  background: #bbada0;
  border-radius: 5px;
  box-shadow: none;
}
.gameboard::before {
  content: "";
  display: block;
  padding-bottom: 100%;
}

/**/
/*
  Grid:
  Creates the static grid background and individual grid cells;
*/
.grid {
  width: 100%;
  height: 100%;
  position: absolute;
  top: 0;
  bottom: 0;
  right: 0;
  left: 0;
  margin: auto;
}
.grid_cell, .tile {
  display: inline-block;
  height: 25%;
  width: 25%;
  padding: 8px;
  float: left;
  background-clip: content-box;
}
.grid_cell {
  background: #cdc1b4;
}

/**/
/*
  Tile container:
  Contains the dynamically-generated tiles;
  absolutely positioned over gameboard to match grid dimensions;
*/
.tile-container {
  /* absolutely positioned over gameboard to match dimensions */
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  margin: auto;
  border-radius: 5px;
}

.tile {
  display: table;
  background: transparent;
  background-clip: content-box;
  position: absolute;
  z-index: 2;
  will-change: top, left;
  transition-property: top, left;
  transition-duration: 0.175s;
  transition-timing-function: ease-out;
}
.tile.initialize {
  -webkit-animation-name: newTile;
          animation-name: newTile;
  -webkit-animation-duration: 0.175s;
          animation-duration: 0.175s;
  -webkit-animation-timing-function: linear;
          animation-timing-function: linear;
  -webkit-animation-fill-mode: forwards;
          animation-fill-mode: forwards;
}
@-webkit-keyframes newTile {
  0% {
    opacity: 0;
  }
  50% {
    opacity: 0;
    transform: scale(0);
  }
  75% {
    opacity: 1;
    transform: scale(0.5);
  }
  100% {
    opacity: 1;
    transform: scale(1);
  }
}
@keyframes newTile {
  0% {
    opacity: 0;
  }
  50% {
    opacity: 0;
    transform: scale(0);
  }
  75% {
    opacity: 1;
    transform: scale(0.5);
  }
  100% {
    opacity: 1;
    transform: scale(1);
  }
}
.tile_number {
  display: table-cell;
  vertical-align: middle;
  text-align: center;
  font-size: 2rem;
  font-weight: bold;
  color: #776e65;
  border-radius: 3px;
}

.tile:nth-of-type(1) {
  z-index: 2;
}

.tile:nth-of-type(2) {
  z-index: 3;
}

.tile:nth-of-type(3) {
  z-index: 4;
}

.tile:nth-of-type(4) {
  z-index: 5;
}

.tile:nth-of-type(5) {
  z-index: 6;
}

.tile:nth-of-type(6) {
  z-index: 7;
}

.tile:nth-of-type(7) {
  z-index: 8;
}

.tile:nth-of-type(8) {
  z-index: 9;
}

.tile:nth-of-type(9) {
  z-index: 10;
}

.tile:nth-of-type(10) {
  z-index: 11;
}

.tile:nth-of-type(11) {
  z-index: 12;
}

.tile:nth-of-type(12) {
  z-index: 13;
}

.tile:nth-of-type(13) {
  z-index: 14;
}

.tile:nth-of-type(14) {
  z-index: 15;
}

.tile:nth-of-type(15) {
  z-index: 16;
}

.tile:nth-of-type(16) {
  z-index: 17;
}

.tile[data-x="0"][data-y="0"] {
  top: 0%;
  left: 0%;
}

.tile[data-x="0"][data-y="25"] {
  top: 25%;
  left: 0%;
}

.tile[data-x="0"][data-y="50"] {
  top: 50%;
  left: 0%;
}

.tile[data-x="0"][data-y="75"] {
  top: 75%;
  left: 0%;
}

.tile[data-x="0"][data-y="100"] {
  top: 100%;
  left: 0%;
}

.tile[data-x="25"][data-y="0"] {
  top: 0%;
  left: 25%;
}

.tile[data-x="25"][data-y="25"] {
  top: 25%;
  left: 25%;
}

.tile[data-x="25"][data-y="50"] {
  top: 50%;
  left: 25%;
}

.tile[data-x="25"][data-y="75"] {
  top: 75%;
  left: 25%;
}

.tile[data-x="25"][data-y="100"] {
  top: 100%;
  left: 25%;
}

.tile[data-x="50"][data-y="0"] {
  top: 0%;
  left: 50%;
}

.tile[data-x="50"][data-y="25"] {
  top: 25%;
  left: 50%;
}

.tile[data-x="50"][data-y="50"] {
  top: 50%;
  left: 50%;
}

.tile[data-x="50"][data-y="75"] {
  top: 75%;
  left: 50%;
}

.tile[data-x="50"][data-y="100"] {
  top: 100%;
  left: 50%;
}

.tile[data-x="75"][data-y="0"] {
  top: 0%;
  left: 75%;
}

.tile[data-x="75"][data-y="25"] {
  top: 25%;
  left: 75%;
}

.tile[data-x="75"][data-y="50"] {
  top: 50%;
  left: 75%;
}

.tile[data-x="75"][data-y="75"] {
  top: 75%;
  left: 75%;
}

.tile[data-x="75"][data-y="100"] {
  top: 100%;
  left: 75%;
}

.tile[data-x="100"][data-y="0"] {
  top: 0%;
  left: 100%;
}

.tile[data-x="100"][data-y="25"] {
  top: 25%;
  left: 100%;
}

.tile[data-x="100"][data-y="50"] {
  top: 50%;
  left: 100%;
}

.tile[data-x="100"][data-y="75"] {
  top: 75%;
  left: 100%;
}

.tile[data-x="100"][data-y="100"] {
  top: 100%;
  left: 100%;
}

.tile_number[data-value="2"] {
  background: #eee4da;
  color: #776e65;
}

.tile_number[data-value="4"] {
  background: #ede0c8;
  color: #776e65;
}

.tile_number[data-value="8"] {
  background: #f2b179;
  color: #f9f6f2;
}

.tile_number[data-value="16"] {
  background: #f59563;
  color: #f9f6f2;
}

.tile_number[data-value="32"] {
  background: #f67c5f;
  color: #f9f6f2;
}

.tile_number[data-value="64"] {
  background: #f65e3b;
  color: #f9f6f2;
}

.tile_number[data-value="128"] {
  background: #edcf72;
  color: #f9f6f2;
}

.tile_number[data-value="256"] {
  background: #edcc61;
  color: #f9f6f2;
}

.tile_number[data-value="512"] {
  background: #edc850;
  color: #f9f6f2;
}

.tile_number[data-value="1024"] {
  background: #edc53f;
  color: #f9f6f2;
}

.tile_number[data-value="2048"] {
  background: #edc22e;
  color: #f9f6f2;
}