:root {
  --size: 4;
  --gap: 14px;
  --board-size: 460px;
  --cell-size: calc((var(--board-size) - (var(--size) + 1) * var(--gap)) / var(--size));
  --bg: #faf8ef;
  --board-bg: #bbada0;
  --cell-bg: rgba(238, 228, 218, 0.35);
  --text-dark: #776e65;
  --text-light: #f9f6f2;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: "Segoe UI", "Clear Sans", Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text-dark);
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: flex-start;
  padding: 24px 16px;
  -webkit-tap-highlight-color: transparent;
}

.container {
  width: 100%;
  max-width: var(--board-size);
}

header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 18px;
  gap: 12px;
}

h1 {
  font-size: 64px;
  font-weight: 800;
  line-height: 1;
  color: var(--text-dark);
}

.subtitle {
  margin-top: 6px;
  font-size: 14px;
  color: #8f8579;
}

.scores {
  display: flex;
  gap: 10px;
}

.score-box {
  background: var(--board-bg);
  border-radius: 8px;
  padding: 8px 18px;
  text-align: center;
  display: flex;
  flex-direction: column;
  min-width: 92px;
  position: relative;
}

.score-label {
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 1px;
  color: #eee4da;
}

.score-value {
  font-size: 24px;
  font-weight: 800;
  color: #fff;
}

.score-add {
  position: absolute;
  left: 0;
  right: 0;
  top: 12px;
  font-size: 22px;
  font-weight: 800;
  color: rgba(119, 110, 101, 0.9);
  animation: scoreUp 0.6s ease-in both;
  pointer-events: none;
}

@keyframes scoreUp {
  0% { opacity: 1; transform: translateY(0); }
  100% { opacity: 0; transform: translateY(-26px); }
}

.controls {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 16px;
  gap: 12px;
  flex-wrap: wrap;
}

.hint {
  font-size: 13px;
  color: #8f8579;
  flex: 1;
  min-width: 140px;
}

.btn {
  background: #8f7a66;
  color: var(--text-light);
  border: none;
  border-radius: 8px;
  padding: 11px 18px;
  font-size: 15px;
  font-weight: 700;
  cursor: pointer;
  transition: background 0.15s ease, transform 0.1s ease;
}

.btn:hover { background: #9f8b77; }
.btn:active { transform: scale(0.96); }

.board-wrapper {
  position: relative;
  width: var(--board-size);
  max-width: 100%;
  aspect-ratio: 1 / 1;
  background: var(--board-bg);
  border-radius: 12px;
  padding: var(--gap);
  touch-action: none;
  margin: 0 auto;
}

.grid-bg {
  position: absolute;
  inset: var(--gap);
  display: grid;
  grid-template-columns: repeat(var(--size), 1fr);
  grid-template-rows: repeat(var(--size), 1fr);
  gap: var(--gap);
}

.grid-cell {
  background: var(--cell-bg);
  border-radius: 8px;
}

.tile-container {
  position: absolute;
  inset: var(--gap);
}

.tile {
  position: absolute;
  top: 0;
  left: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  border-radius: 8px;
  font-weight: 800;
  font-size: 34px;
  background: #eee4da;
  color: var(--text-dark);
  transition: transform 0.12s ease-in-out;
  z-index: 10;
}

.tile-new {
  animation: appear 0.18s ease 0.05s backwards;
}

@keyframes appear {
  0% { transform: scale(0); }
  100% { transform: scale(1); }
}

.tile-merged {
  animation: pop 0.18s ease;
  z-index: 20;
}

@keyframes pop {
  0% { transform: scale(1); }
  50% { transform: scale(1.18); }
  100% { transform: scale(1); }
}

/* Tile colors */
.tile-2    { background: #eee4da; color: #776e65; }
.tile-4    { background: #ede0c8; color: #776e65; }
.tile-8    { background: #f2b179; color: #f9f6f2; }
.tile-16   { background: #f59563; color: #f9f6f2; }
.tile-32   { background: #f67c5f; color: #f9f6f2; }
.tile-64   { background: #f65e3b; color: #f9f6f2; }
.tile-128  { background: #edcf72; color: #f9f6f2; font-size: 30px; }
.tile-256  { background: #edcc61; color: #f9f6f2; font-size: 30px; }
.tile-512  { background: #edc850; color: #f9f6f2; font-size: 30px; }
.tile-1024 { background: #edc53f; color: #f9f6f2; font-size: 24px; }
.tile-2048 { background: #edc22e; color: #f9f6f2; font-size: 24px; box-shadow: 0 0 24px 6px rgba(237, 194, 46, 0.6); }
.tile-super { background: #3c3a32; color: #f9f6f2; font-size: 22px; }

.game-message {
  position: absolute;
  inset: 0;
  background: rgba(238, 228, 218, 0.73);
  border-radius: 12px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 18px;
  z-index: 100;
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.3s ease;
}

.game-message.show {
  opacity: 1;
  visibility: visible;
  animation: fadeIn 0.8s ease;
}

.game-message.win { background: rgba(237, 194, 46, 0.55); }

@keyframes fadeIn {
  0% { opacity: 0; }
  100% { opacity: 1; }
}

#message-text {
  font-size: 44px;
  font-weight: 800;
  color: #776e65;
}

footer {
  margin-top: 22px;
  font-size: 13px;
  line-height: 1.5;
  color: #8f8579;
  border-top: 2px solid #d8cdbf;
  padding-top: 14px;
}

.credits {
  margin-top: 8px;
  font-size: 12px;
  color: #a59b8c;
  text-align: right;
}

@media (max-width: 520px) {
  :root { --board-size: 92vw; --gap: 11px; }
  h1 { font-size: 46px; }
  .tile { font-size: 26px; }
  .tile-128, .tile-256, .tile-512 { font-size: 22px; }
  .tile-1024, .tile-2048 { font-size: 18px; }
  .score-box { min-width: 72px; padding: 6px 12px; }
  #message-text { font-size: 32px; }
}