/* ============================================
   GLASSMORPHISM 2048 - COMPLETE CSS
   ============================================ */

/* ============================================
   KEYFRAME ANIMATIONS
   ============================================ */

@keyframes gradient-shift {
  0% {
    background-position: 0% 50%;
  }
  50% {
    background-position: 100% 50%;
  }
  100% {
    background-position: 0% 50%;
  }
}

@keyframes blob-float-1 {
  0%, 100% {
    transform: translate(0, 0) scale(1);
    opacity: 0.8;
  }
  25% {
    transform: translate(30px, -30px) scale(1.1);
  }
  50% {
    transform: translate(-20px, 20px) scale(0.9);
    opacity: 0.6;
  }
  75% {
    transform: translate(40px, 10px) scale(1.05);
  }
}

@keyframes blob-float-2 {
  0%, 100% {
    transform: translate(0, 0) scale(1);
    opacity: 0.7;
  }
  25% {
    transform: translate(-40px, 30px) scale(0.95);
  }
  50% {
    transform: translate(30px, -20px) scale(1.1);
    opacity: 0.5;
  }
  75% {
    transform: translate(-30px, -30px) scale(0.9);
  }
}

@keyframes blob-float-3 {
  0%, 100% {
    transform: translate(0, 0) scale(1);
    opacity: 0.6;
  }
  25% {
    transform: translate(25px, 40px) scale(1.05);
  }
  50% {
    transform: translate(-35px, -25px) scale(0.95);
    opacity: 0.4;
  }
  75% {
    transform: translate(35px, -35px) scale(1.1);
  }
}

@keyframes move-up {
  0% {
    top: 25px;
    opacity: 1;
  }
  100% {
    top: -50px;
    opacity: 0;
  }
}

@keyframes fade-in {
  0% {
    opacity: 0;
  }
  100% {
    opacity: 1;
  }
}

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

@keyframes pop {
  0% {
    transform: scale(0.8);
    opacity: 0.6;
  }
  50% {
    transform: scale(1.15);
    opacity: 1;
  }
  100% {
    transform: scale(1);
    opacity: 1;
  }
}

/* ============================================
   BASE STYLES
   ============================================ */

html, body {
  margin: 0;
  padding: 0;
  background: linear-gradient(-45deg, #0f0f1e, #1a0f2e, #0a1a3a, #1a0a2e);
  background-size: 400% 400%;
  color: #e0e0e0;
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  font-size: 18px;
  min-height: 100vh;
  animation: gradient-shift 15s ease infinite;
  position: relative;
  overflow-x: hidden;
}

body {
  margin: 80px 0;
}

body::before {
  content: '';
  position: fixed;
  top: 0;
  left: 0;
  width: 200%;
  height: 200%;
  background: radial-gradient(circle at 20% 30%, rgba(147, 51, 234, 0.15) 0%, transparent 50%),
              radial-gradient(circle at 80% 70%, rgba(59, 130, 246, 0.15) 0%, transparent 50%),
              radial-gradient(circle at 40% 80%, rgba(0, 188, 212, 0.1) 0%, transparent 50%);
  pointer-events: none;
  z-index: 0;
}

body::after {
  content: '';
  position: fixed;
  top: -50%;
  right: -50%;
  width: 200%;
  height: 200%;
  background: radial-gradient(circle, rgba(139, 92, 246, 0.08) 0%, transparent 70%);
  pointer-events: none;
  z-index: 0;
  animation: blob-float-1 20s ease-in-out infinite;
}

/* ============================================
   CONTAINER & LAYOUT
   ============================================ */

.container {
  width: 500px;
  margin: 0 auto;
  position: relative;
  z-index: 1;
}

.heading {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 20px;
}

.heading::after {
  content: '';
  display: block;
  clear: both;
}

h1.title {
  font-size: 80px;
  font-weight: 700;
  margin: 0;
  background: linear-gradient(135deg, #a78bfa 0%, #60a5fa 50%, #06b6d4 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  letter-spacing: -2px;
}

.scores-container {
  display: flex;
  gap: 12px;
  align-items: center;
}

.score-container, .best-container {
  position: relative;
  background: rgba(255, 255, 255, 0.1);
  backdrop-filter: blur(10px);
  border: 1px solid rgba(255, 255, 255, 0.2);
  padding: 15px 25px;
  font-size: 25px;
  height: 25px;
  line-height: 47px;
  font-weight: 600;
  border-radius: 12px;
  color: #fff;
  text-align: center;
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1),
              inset 0 1px 1px rgba(255, 255, 255, 0.2);
  transition: all 0.3s ease;
}

.score-container:hover, .best-container:hover {
  background: rgba(255, 255, 255, 0.15);
  box-shadow: 0 12px 40px rgba(167, 139, 250, 0.2),
              inset 0 1px 1px rgba(255, 255, 255, 0.3);
}

.score-container::after, .best-container::after {
  position: absolute;
  width: 100%;
  top: 10px;
  left: 0;
  text-transform: uppercase;
  font-size: 13px;
  line-height: 13px;
  text-align: center;
  color: rgba(255, 255, 255, 0.7);
  font-weight: 500;
  letter-spacing: 0.5px;
}

.score-container::after {
  content: 'Score';
}

.best-container::after {
  content: 'Best';
}

.score-container .score-addition, .best-container .score-addition {
  position: absolute;
  right: 30px;
  color: #60a5fa;
  font-size: 25px;
  line-height: 25px;
  font-weight: 700;
  z-index: 100;
  animation: move-up 600ms ease-in both;
}

/* ============================================
   TYPOGRAPHY
   ============================================ */

p {
  margin-top: 0;
  margin-bottom: 10px;
  line-height: 1.65;
}

a {
  color: #60a5fa;
  font-weight: 600;
  text-decoration: none;
  cursor: pointer;
  transition: color 0.3s ease;
  border-bottom: 1px solid transparent;
}

a:hover {
  color: #a78bfa;
  border-bottom-color: #a78bfa;
}

strong.important {
  text-transform: uppercase;
  font-weight: 700;
  letter-spacing: 0.5px;
  color: #a78bfa;
}

hr {
  border: none;
  border-bottom: 1px solid rgba(255, 255, 255, 0.1);
  margin-top: 20px;
  margin-bottom: 30px;
}

.game-explanation {
  margin-top: 50px;
  color: rgba(255, 255, 255, 0.8);
}

.attribution {
  margin-top: 30px;
  text-align: center;
  font-size: 14px;
  color: rgba(255, 255, 255, 0.6);
}

/* ============================================
   AD SPACES
   ============================================ */

#ad-space-top, #ad-space-bottom {
  display: none;
}

/* ============================================
   ABOVE GAME SECTION
   ============================================ */

.above-game {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 20px;
  gap: 20px;
}

.above-game::after {
  content: '';
  display: block;
  clear: both;
}

.game-intro {
  flex: 1;
  line-height: 42px;
  margin-bottom: 0;
  color: rgba(255, 255, 255, 0.9);
}

.restart-button {
  display: inline-block;
  background: rgba(96, 165, 250, 0.2);
  backdrop-filter: blur(10px);
  border: 1.5px solid rgba(96, 165, 250, 0.4);
  border-radius: 24px;
  padding: 0 28px;
  text-decoration: none;
  color: #60a5fa;
  height: 40px;
  line-height: 40px;
  text-align: center;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.3s ease;
  box-shadow: 0 4px 15px rgba(96, 165, 250, 0.1);
}

.restart-button:hover {
  background: rgba(96, 165, 250, 0.3);
  border-color: rgba(96, 165, 250, 0.6);
  box-shadow: 0 8px 25px rgba(96, 165, 250, 0.25),
              0 0 20px rgba(96, 165, 250, 0.15);
  color: #fff;
}

.restart-button:active {
  transform: scale(0.98);
}

/* ============================================
   GAME CONTAINER
   ============================================ */

.game-container {
  margin-top: 20px;
  position: relative;
  padding: 0;
  cursor: default;
  -webkit-touch-callout: none;
  -ms-touch-callout: none;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  -ms-touch-action: none;
  touch-action: none;
  background: rgba(255, 255, 255, 0.08);
  backdrop-filter: blur(20px);
  border: 1.5px solid rgba(255, 255, 255, 0.15);
  border-radius: 20px;
  width: 500px;
  height: 500px;
  box-sizing: border-box;
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3),
              inset 0 1px 1px rgba(255, 255, 255, 0.1);
  overflow: hidden;
}

.game-container .game-message {
  display: none;
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  background: rgba(15, 15, 30, 0.6);
  backdrop-filter: blur(8px);
  z-index: 100;
  text-align: center;
  animation: fade-in 800ms ease 1200ms both;
}

.game-container .game-message p {
  font-size: 60px;
  font-weight: 700;
  height: 60px;
  line-height: 60px;
  margin-top: 180px;
  color: #fff;
}

.game-container .game-message .lower {
  display: block;
  margin-top: 40px;
}

.game-container .game-message a {
  display: inline-block;
  background: rgba(167, 139, 250, 0.25);
  backdrop-filter: blur(10px);
  border: 1.5px solid rgba(167, 139, 250, 0.4);
  border-radius: 12px;
  padding: 0 24px;
  text-decoration: none;
  color: #a78bfa;
  height: 40px;
  line-height: 40px;
  margin: 0 6px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.3s ease;
  box-shadow: 0 4px 15px rgba(167, 139, 250, 0.1);
}

.game-container .game-message a:hover {
  background: rgba(167, 139, 250, 0.35);
  border-color: rgba(167, 139, 250, 0.6);
  box-shadow: 0 8px 25px rgba(167, 139, 250, 0.25),
              0 0 20px rgba(167, 139, 250, 0.15);
  color: #fff;
}

.game-container .game-message a.keep-playing-button {
  display: none;
}

.game-container .game-message.game-won {
  background: rgba(34, 197, 94, 0.1);
  backdrop-filter: blur(12px);
  color: #86efac;
}

.game-container .game-message.game-won a.keep-playing-button {
  display: inline-block;
}

.game-container .game-message.game-over {
  background: rgba(239, 68, 68, 0.1);
  backdrop-filter: blur(12px);
}

.game-container .game-message.game-won,
.game-container .game-message.game-over {
  display: block;
}

/* ============================================
   GRID
   ============================================ */

.grid-container {
  position: absolute;
  z-index: 1;
  padding: 15px;
}

.grid-row {
  margin-bottom: 15px;
  display: flex;
  gap: 15px;
}

.grid-row:last-child {
  margin-bottom: 0;
}

.grid-row::after {
  content: '';
  display: block;
  clear: both;
}

.grid-cell {
  width: 107px;
  height: 107px;
  float: left;
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.06);
  backdrop-filter: blur(10px);
  border: 1px solid rgba(255, 255, 255, 0.1);
  box-shadow: inset 0 1px 1px rgba(255, 255, 255, 0.08);
  transition: all 0.3s ease;
}

.grid-cell:last-child {
  margin-right: 0;
}

/* ============================================
   TILE POSITIONS (DESKTOP - 500px)
   ============================================ */

.tile-container {
  position: absolute;
  z-index: 2;
  padding: 15px;
}

.tile, .tile .tile-inner {
  width: 107px;
  height: 107px;
  line-height: 107px;
}

.tile {
  position: absolute;
  transition: 100ms ease-in-out;
  transition-property: transform;
}

/* Position transforms - Column 1 */
.tile.tile-position-1-1 {
  transform: translate(0px, 0px);
}

.tile.tile-position-1-2 {
  transform: translate(0px, 121px);
}

.tile.tile-position-1-3 {
  transform: translate(0px, 242px);
}

.tile.tile-position-1-4 {
  transform: translate(0px, 363px);
}

/* Position transforms - Column 2 */
.tile.tile-position-2-1 {
  transform: translate(121px, 0px);
}

.tile.tile-position-2-2 {
  transform: translate(121px, 121px);
}

.tile.tile-position-2-3 {
  transform: translate(121px, 242px);
}

.tile.tile-position-2-4 {
  transform: translate(121px, 363px);
}

/* Position transforms - Column 3 */
.tile.tile-position-3-1 {
  transform: translate(242px, 0px);
}

.tile.tile-position-3-2 {
  transform: translate(242px, 121px);
}

.tile.tile-position-3-3 {
  transform: translate(242px, 242px);
}

.tile.tile-position-3-4 {
  transform: translate(242px, 363px);
}

/* Position transforms - Column 4 */
.tile.tile-position-4-1 {
  transform: translate(363px, 0px);
}

.tile.tile-position-4-2 {
  transform: translate(363px, 121px);
}

.tile.tile-position-4-3 {
  transform: translate(363px, 242px);
}

.tile.tile-position-4-4 {
  transform: translate(363px, 363px);
}

/* ============================================
   TILE INNER (CONTENT)
   ============================================ */

.tile .tile-inner {
  border-radius: 14px;
  text-align: center;
  font-weight: 700;
  z-index: 10;
  font-size: 55px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: linear-gradient(135deg, rgba(255, 255, 255, 0.14) 0%, rgba(255, 255, 255, 0.06) 100%);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid rgba(255, 255, 255, 0.18);
  border-top-color: rgba(255, 255, 255, 0.3);
  border-left-color: rgba(255, 255, 255, 0.25);
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.15),
              inset 0 1px 0 rgba(255, 255, 255, 0.15),
              inset 0 -1px 0 rgba(0, 0, 0, 0.05);
  color: #fff;
  text-shadow: 0 1px 3px rgba(0, 0, 0, 0.3);
}

/* ============================================
   TILE COLORS & VALUES
   ============================================ */

/* --- Tile 2: 맑은 유리 --- */
.tile.tile-2 .tile-inner {
  background: linear-gradient(135deg, rgba(200, 210, 230, 0.22) 0%, rgba(180, 195, 220, 0.10) 100%);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 1px solid rgba(200, 210, 230, 0.35);
  border-top-color: rgba(220, 230, 250, 0.45);
  box-shadow: 0 8px 28px rgba(0, 0, 0, 0.12),
              inset 0 1px 0 rgba(255, 255, 255, 0.25),
              inset 0 -1px 0 rgba(0, 0, 0, 0.05);
  color: rgba(230, 235, 245, 0.95);
  text-shadow: 0 1px 3px rgba(0, 0, 0, 0.25);
}

/* --- Tile 4: 따뜻한 유리 (가독성 강화) --- */
.tile.tile-4 .tile-inner {
  background: linear-gradient(135deg, rgba(210, 190, 160, 0.28) 0%, rgba(190, 165, 130, 0.14) 100%);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 1px solid rgba(230, 210, 180, 0.4);
  border-top-color: rgba(245, 230, 200, 0.5);
  box-shadow: 0 8px 28px rgba(0, 0, 0, 0.15),
              inset 0 1px 0 rgba(255, 240, 210, 0.22),
              inset 0 -1px 0 rgba(0, 0, 0, 0.06);
  color: #ffffff;
  text-shadow: 0 1px 4px rgba(0, 0, 0, 0.45), 0 0 8px rgba(0, 0, 0, 0.2);
}

/* --- Tile 8: 오렌지 유리 --- */
.tile.tile-8 .tile-inner {
  background: linear-gradient(135deg, rgba(249, 140, 50, 0.22) 0%, rgba(230, 100, 30, 0.10) 100%);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 1px solid rgba(249, 140, 50, 0.4);
  border-top-color: rgba(255, 170, 80, 0.5);
  box-shadow: 0 8px 30px rgba(249, 115, 22, 0.15),
              inset 0 1px 0 rgba(255, 200, 150, 0.2),
              inset 0 -1px 0 rgba(0, 0, 0, 0.05);
  color: #fff;
  text-shadow: 0 1px 4px rgba(180, 70, 0, 0.4);
}

/* --- Tile 16: 진한 오렌지 유리 --- */
.tile.tile-16 .tile-inner {
  background: linear-gradient(135deg, rgba(245, 100, 50, 0.22) 0%, rgba(220, 70, 30, 0.10) 100%);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 1px solid rgba(245, 100, 50, 0.45);
  border-top-color: rgba(255, 140, 90, 0.5);
  box-shadow: 0 8px 30px rgba(239, 68, 68, 0.15),
              inset 0 1px 0 rgba(255, 180, 150, 0.18),
              inset 0 -1px 0 rgba(0, 0, 0, 0.05);
  color: #fff;
  text-shadow: 0 1px 4px rgba(160, 40, 0, 0.4);
}

/* --- Tile 32: 레드 오렌지 유리 --- */
.tile.tile-32 .tile-inner {
  background: linear-gradient(135deg, rgba(230, 50, 50, 0.22) 0%, rgba(200, 30, 30, 0.10) 100%);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 1px solid rgba(230, 50, 50, 0.45);
  border-top-color: rgba(255, 100, 100, 0.5);
  box-shadow: 0 8px 30px rgba(220, 38, 38, 0.15),
              inset 0 1px 0 rgba(255, 150, 150, 0.18),
              inset 0 -1px 0 rgba(0, 0, 0, 0.05);
  color: #fff;
  text-shadow: 0 1px 4px rgba(140, 20, 20, 0.4);
}

/* --- Tile 64: 레드 유리 --- */
.tile.tile-64 .tile-inner {
  background: linear-gradient(135deg, rgba(200, 25, 25, 0.25) 0%, rgba(170, 15, 15, 0.12) 100%);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 1px solid rgba(200, 25, 25, 0.5);
  border-top-color: rgba(240, 80, 80, 0.5);
  box-shadow: 0 8px 30px rgba(191, 18, 18, 0.18),
              inset 0 1px 0 rgba(255, 130, 130, 0.15),
              inset 0 -1px 0 rgba(0, 0, 0, 0.05);
  color: #fff;
  text-shadow: 0 1px 4px rgba(120, 10, 10, 0.5);
}

/* --- Tile 128: 골드 유리 (글로우 시작) --- */
.tile.tile-128 .tile-inner {
  background: linear-gradient(135deg, rgba(250, 204, 21, 0.22) 0%, rgba(220, 170, 10, 0.10) 100%);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 1px solid rgba(250, 204, 21, 0.45);
  border-top-color: rgba(255, 225, 80, 0.55);
  box-shadow: 0 8px 35px rgba(250, 204, 21, 0.2),
              0 0 15px rgba(250, 204, 21, 0.1),
              inset 0 1px 0 rgba(255, 240, 150, 0.2);
  font-size: 45px;
  color: #fff;
  text-shadow: 0 0 10px rgba(250, 204, 21, 0.3), 0 1px 3px rgba(0, 0, 0, 0.3);
}

/* --- Tile 256: 밝은 골드 유리 --- */
.tile.tile-256 .tile-inner {
  background: linear-gradient(135deg, rgba(250, 204, 21, 0.25) 0%, rgba(220, 170, 10, 0.12) 100%);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 1px solid rgba(250, 204, 21, 0.5);
  border-top-color: rgba(255, 225, 80, 0.6);
  box-shadow: 0 8px 38px rgba(250, 204, 21, 0.25),
              0 0 20px rgba(250, 204, 21, 0.12),
              inset 0 1px 0 rgba(255, 240, 150, 0.2);
  font-size: 45px;
  color: #fff;
  text-shadow: 0 0 12px rgba(250, 204, 21, 0.35), 0 1px 3px rgba(0, 0, 0, 0.3);
}

/* --- Tile 512: 강한 골드 유리 --- */
.tile.tile-512 .tile-inner {
  background: linear-gradient(135deg, rgba(250, 204, 21, 0.28) 0%, rgba(220, 170, 10, 0.14) 100%);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 1px solid rgba(250, 204, 21, 0.55);
  border-top-color: rgba(255, 225, 80, 0.65);
  box-shadow: 0 8px 40px rgba(250, 204, 21, 0.3),
              0 0 25px rgba(250, 204, 21, 0.15),
              inset 0 1px 0 rgba(255, 240, 150, 0.2);
  font-size: 45px;
  color: #fff;
  text-shadow: 0 0 14px rgba(250, 204, 21, 0.4), 0 1px 3px rgba(0, 0, 0, 0.3);
}

/* --- Tile 1024: 빛나는 골드 유리 --- */
.tile.tile-1024 .tile-inner {
  background: linear-gradient(135deg, rgba(250, 204, 21, 0.3) 0%, rgba(220, 170, 10, 0.16) 100%);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 1px solid rgba(250, 204, 21, 0.6);
  border-top-color: rgba(255, 225, 80, 0.7);
  box-shadow: 0 8px 42px rgba(250, 204, 21, 0.35),
              0 0 30px rgba(250, 204, 21, 0.18),
              inset 0 1px 0 rgba(255, 240, 150, 0.22);
  font-size: 35px;
  color: #fff;
  text-shadow: 0 0 16px rgba(250, 204, 21, 0.45), 0 1px 3px rgba(0, 0, 0, 0.3);
}

/* --- Tile 2048: 최강 골드 유리 --- */
.tile.tile-2048 .tile-inner {
  background: linear-gradient(135deg, rgba(250, 204, 21, 0.35) 0%, rgba(220, 170, 10, 0.18) 100%);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 1.5px solid rgba(250, 204, 21, 0.65);
  border-top-color: rgba(255, 225, 80, 0.75);
  box-shadow: 0 8px 45px rgba(250, 204, 21, 0.4),
              0 0 35px rgba(250, 204, 21, 0.2),
              inset 0 1px 0 rgba(255, 240, 150, 0.25);
  font-size: 35px;
  color: #fff;
  text-shadow: 0 0 18px rgba(250, 204, 21, 0.5), 0 1px 3px rgba(0, 0, 0, 0.3);
}

/* --- Tile Super: 다크 골드 보더 유리 --- */
.tile.tile-super .tile-inner {
  background: linear-gradient(135deg, rgba(15, 15, 30, 0.5) 0%, rgba(30, 20, 50, 0.35) 100%);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 2px solid rgba(250, 204, 21, 0.55);
  border-top-color: rgba(255, 225, 80, 0.65);
  box-shadow: 0 8px 40px rgba(250, 204, 21, 0.25),
              0 0 30px rgba(250, 204, 21, 0.12),
              inset 0 1px 0 rgba(255, 240, 150, 0.1);
  font-size: 30px;
  color: #facc15;
  text-shadow: 0 0 18px rgba(250, 204, 21, 0.5), 0 1px 3px rgba(0, 0, 0, 0.4);
}

/* ============================================
   TILE ANIMATIONS
   ============================================ */

.tile-new .tile-inner {
  animation: appear 200ms ease 100ms backwards;
}

.tile-merged .tile-inner {
  z-index: 20;
  animation: pop 250ms cubic-bezier(0.34, 1.56, 0.64, 1) 80ms backwards;
  box-shadow: 0 0 25px rgba(167, 139, 250, 0.35),
              0 8px 32px rgba(0, 0, 0, 0.15),
              inset 0 1px 1px rgba(255, 255, 255, 0.2);
}

/* ============================================
   MOBILE RESPONSIVE (max-width: 520px)
   ============================================ */

@media screen and (max-width: 520px) {
  html, body {
    font-size: 15px;
  }

  body {
    margin: 20px 0;
    padding: 0 20px;
  }

  h1.title {
    font-size: 32px;
    margin-top: 15px;
  }

  .container {
    width: 280px;
    margin: 0 auto;
  }

  .score-container, .best-container {
    margin-top: 0;
    padding: 12px 10px;
    min-width: 40px;
    font-size: 14px;
    height: 14px;
    line-height: 36px;
  }

  .heading {
    margin-bottom: 10px;
  }

  .above-game {
    flex-direction: column;
    gap: 10px;
    margin-bottom: 15px;
  }

  .game-intro {
    width: 100%;
    display: block;
    box-sizing: border-box;
    line-height: 1.65;
    font-size: 14px;
  }

  .restart-button {
    width: 100%;
    padding: 0;
    display: block;
    box-sizing: border-box;
  }

  /* Game Container Mobile */
  .game-container {
    margin-top: 15px;
    position: relative;
    padding: 0;
    cursor: default;
    -webkit-touch-callout: none;
    -ms-touch-callout: none;
    -webkit-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    -ms-touch-action: none;
    touch-action: none;
    background: rgba(255, 255, 255, 0.08);
    backdrop-filter: blur(20px);
    border: 1.5px solid rgba(255, 255, 255, 0.15);
    border-radius: 16px;
    width: 280px;
    height: 280px;
    box-sizing: border-box;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3),
                inset 0 1px 1px rgba(255, 255, 255, 0.1);
  }

  .game-container .game-message {
    display: none;
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    background: rgba(15, 15, 30, 0.6);
    backdrop-filter: blur(8px);
    z-index: 100;
    text-align: center;
    animation: fade-in 800ms ease 1200ms both;
  }

  .game-container .game-message p {
    font-size: 30px;
    font-weight: 700;
    height: 30px;
    line-height: 30px;
    margin-top: 90px;
    color: #fff;
  }

  .game-container .game-message .lower {
    display: block;
    margin-top: 30px;
  }

  .game-container .game-message a {
    display: inline-block;
    background: rgba(167, 139, 250, 0.25);
    backdrop-filter: blur(10px);
    border: 1.5px solid rgba(167, 139, 250, 0.4);
    border-radius: 10px;
    padding: 0 16px;
    text-decoration: none;
    color: #a78bfa;
    height: 32px;
    line-height: 32px;
    margin: 0 4px;
    font-weight: 600;
    font-size: 13px;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 4px 15px rgba(167, 139, 250, 0.1);
  }

  .game-container .game-message a.keep-playing-button {
    display: none;
  }

  .game-container .game-message.game-won a.keep-playing-button {
    display: inline-block;
  }

  /* Grid Mobile */
  .grid-container {
    position: absolute;
    z-index: 1;
    padding: 10px;
  }

  .grid-row {
    margin-bottom: 10px;
    display: flex;
    gap: 10px;
  }

  .grid-row:last-child {
    margin-bottom: 0;
  }

  .grid-cell {
    width: 58px;
    height: 58px;
    float: left;
    border-radius: 10px;
    background: rgba(255, 255, 255, 0.06);
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.1);
    box-shadow: inset 0 1px 1px rgba(255, 255, 255, 0.08);
  }

  /* Tiles Mobile */
  .tile, .tile .tile-inner {
    width: 58px;
    height: 58px;
    line-height: 58px;
  }

  /* Mobile Position transforms - Column 1 */
  .tile.tile-position-1-1 {
    transform: translate(0px, 0px);
  }

  .tile.tile-position-1-2 {
    transform: translate(0px, 67px);
  }

  .tile.tile-position-1-3 {
    transform: translate(0px, 135px);
  }

  .tile.tile-position-1-4 {
    transform: translate(0px, 202px);
  }

  /* Mobile Position transforms - Column 2 */
  .tile.tile-position-2-1 {
    transform: translate(67px, 0px);
  }

  .tile.tile-position-2-2 {
    transform: translate(67px, 67px);
  }

  .tile.tile-position-2-3 {
    transform: translate(67px, 135px);
  }

  .tile.tile-position-2-4 {
    transform: translate(67px, 202px);
  }

  /* Mobile Position transforms - Column 3 */
  .tile.tile-position-3-1 {
    transform: translate(135px, 0px);
  }

  .tile.tile-position-3-2 {
    transform: translate(135px, 67px);
  }

  .tile.tile-position-3-3 {
    transform: translate(135px, 135px);
  }

  .tile.tile-position-3-4 {
    transform: translate(135px, 202px);
  }

  /* Mobile Position transforms - Column 4 */
  .tile.tile-position-4-1 {
    transform: translate(202px, 0px);
  }

  .tile.tile-position-4-2 {
    transform: translate(202px, 67px);
  }

  .tile.tile-position-4-3 {
    transform: translate(202px, 135px);
  }

  .tile.tile-position-4-4 {
    transform: translate(202px, 202px);
  }

  .tile .tile-inner {
    font-size: 35px;
  }

  .tile.tile-128 .tile-inner,
  .tile.tile-256 .tile-inner,
  .tile.tile-512 .tile-inner {
    font-size: 20px;
  }

  .tile.tile-1024 .tile-inner,
  .tile.tile-2048 .tile-inner {
    font-size: 18px;
  }

  .tile.tile-super .tile-inner {
    font-size: 10px;
  }
}