:root {
	color-scheme: light;
	--board-size: min(92vw, 500px);
	--gap: clamp(8px, 2vw, 15px);
	--board: #bbada0;
	--ink: #776e65;
}

* { box-sizing: border-box; }

body {
	min-width: 280px;
	margin: 0;
	background: #faf8ef;
	color: var(--ink);
	font-family: Arial, Helvetica, sans-serif;
}

button { font: inherit; }

.game-shell {
	width: var(--board-size);
	margin: 0 auto;
	padding: 28px 0 44px;
}

.game-header, .intro-row, .score-area, .message-actions { display: flex; align-items: center; }

.game-header { justify-content: space-between; gap: 18px; }

.back-link {
	display: inline-block;
	margin-bottom: 5px;
	color: #776e65;
	font-size: .86rem;
	font-weight: 700;
	text-decoration-thickness: 1px;
	text-underline-offset: 3px;
}

h1 {
	margin: 0;
	font-size: clamp(3.5rem, 13vw, 5rem);
	line-height: .8;
	letter-spacing: -4px;
}

.score-area { gap: 6px; }

.score-box {
	min-width: 74px;
	padding: 7px 10px 8px;
	border-radius: 3px;
	background: #bbada0;
	color: #fff;
	text-align: center;
	line-height: 1;
}

.score-box span { display: block; color: #eee4da; font-size: .72rem; font-weight: 700; }
.score-box strong { display: block; margin-top: 3px; font-size: 1.3rem; }

.intro-row { justify-content: space-between; gap: 12px; margin: 23px 0 18px; }
.intro-row p { margin: 0; font-size: 1.05rem; line-height: 1.35; }

#new-game, .message-actions button {
	border: 0;
	border-radius: 3px;
	padding: 10px 15px;
	background: #8f7a66;
	color: #f9f6f2;
	cursor: pointer;
	font-weight: 700;
	white-space: nowrap;
}

#new-game:hover, .message-actions button:hover { background: #776e65; }
#new-game:focus-visible, .message-actions button:focus-visible, .back-link:focus-visible { outline: 3px solid #edc22e; outline-offset: 3px; }

.game-board {
	position: relative;
	width: 100%;
	aspect-ratio: 1;
	border-radius: 6px;
	background: var(--board);
	touch-action: none;
}

.grid-background, .tile-layer { position: absolute; inset: var(--gap); }
.grid-background { display: grid; grid-template-columns: repeat(4, 1fr); gap: var(--gap); }
.grid-background span { border-radius: 4px; background: rgba(238, 228, 218, .35); }
.tile-layer { pointer-events: none; }

.tile {
	position: absolute;
	width: calc((100% - (var(--gap) * 3)) / 4);
	height: calc((100% - (var(--gap) * 3)) / 4);
	display: grid;
	place-items: center;
	border-radius: 4px;
	font-size: clamp(1.5rem, 8vw, 3.45rem);
	font-weight: 700;
	line-height: 1;
	transition: transform 95ms ease-in-out;
}

.moving-tile { z-index: 1; will-change: transform; }
.tile-awaiting-motion { opacity: 0; }

.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: clamp(1.25rem, 6.5vw, 2.8rem); }
.tile-256 { background: #edcc61; color: #f9f6f2; font-size: clamp(1.25rem, 6.5vw, 2.8rem); }
.tile-512 { background: #edc850; color: #f9f6f2; font-size: clamp(1.25rem, 6.5vw, 2.8rem); }
.tile-1024 { background: #edc53f; color: #f9f6f2; font-size: clamp(1rem, 5.2vw, 2.3rem); }
.tile-2048 { background: #edc22e; color: #f9f6f2; font-size: clamp(1rem, 5.2vw, 2.3rem); box-shadow: 0 0 18px 5px rgba(243, 215, 116, .55); }
.tile-super { background: #3c3a32; color: #f9f6f2; font-size: clamp(.9rem, 4.5vw, 2rem); }

.game-message {
	position: absolute;
	inset: 0;
	display: grid;
	place-content: center;
	gap: 20px;
	padding: 20px;
	border-radius: 6px;
	background: rgba(238, 228, 218, .73);
	text-align: center;
	z-index: 2;
}

.game-message[hidden] { display: none; }

.game-message p { margin: 0; color: #776e65; font-size: clamp(2.2rem, 10vw, 3.7rem); font-weight: 700; }
.message-actions { justify-content: center; flex-wrap: wrap; gap: 8px; }

.how-to { margin: 28px 0 0; font-size: .9rem; line-height: 1.55; }

@media (max-width: 420px) {
	.game-shell { padding-top: 20px; }
	.score-box { min-width: 62px; padding-right: 7px; padding-left: 7px; }
	.score-box strong { font-size: 1.1rem; }
	.intro-row p { font-size: .92rem; }
	#new-game { padding: 9px 10px; }
}