:root {
    --bg-color-start: #1e293b;
    --bg-color-end: #0f172a;
    --game-container-bg: #ffffff;
    --grid-cell-bg: #e2e8f0;
    --text-color: #1e293b;
    --text-color-light: #f8fafc;
}

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

body {
    margin: 0;
    padding: 0;
    background: radial-gradient(circle at center, var(--bg-color-start) 0%, var(--bg-color-end) 100%);
    color: var(--text-color-light);
    /* Light text for body background */
    font-family: "Poppins", "Clear Sans", "Helvetica Neue", Arial, sans-serif;
    font-size: 18px;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    touch-action: none;
    /* Prevent default touch actions like pull-to-refresh */
    overscroll-behavior: none;
    /* Prevent bounce effects */
}

.container {
    width: 500px;
    margin: 0 auto;
}

.heading {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 30px;
}

.title-wrapper {
    display: flex;
    flex-direction: column;
}

.brand {
    font-size: 40px;
    font-weight: 700;
    color: #cbd5e1;
    margin-bottom: -15px;
    /* Pull 2048 closer */
    text-shadow: 0 0 10px rgba(255, 255, 255, 0.3);
}

.title {
    font-size: 80px;
    font-weight: 700;
    margin: 0;
    line-height: .9;
    text-shadow: 0 0 10px rgba(255, 255, 255, 0.5);
}

.scores-container {
    text-align: right;
    display: flex;
    gap: 8px;
}

.score-container,
.best-container {
    position: relative;
    background: rgba(255, 255, 255, 0.1);
    padding: 15px 25px;
    font-size: 25px;
    height: 55px;
    line-height: 25px;
    font-weight: bold;
    border-radius: 3px;
    color: white;
    text-align: center;
    display: flex;
    flex-direction: column;
    justify-content: center;
    backdrop-filter: blur(5px);
    box-shadow: 0 0 10px rgba(0, 191, 255, 0.3);
    border: 1px solid rgba(255, 255, 255, 0.2);
}

.score-container::after,
.best-container::after {
    position: absolute;
    width: 100%;
    top: 5px;
    left: 0;
    text-transform: uppercase;
    font-size: 13px;
    line-height: 13px;
    text-align: center;
    color: #cbd5e1;
}

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

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

.game-intro {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    flex-wrap: wrap;
    /* Allow wrapping if needed */
    gap: 10px;
    /* Space between text and button */
}

.game-intro-text {
    line-height: 1.5;
    margin: 0;
    color: #e2e8f0;
}

.buttons-wrapper {
    display: flex;
    gap: 10px;
}

.restart-button,
.undo-button {
    background: #3b82f6;
    /* Blue button */
    border-radius: 3px;
    padding: 0 20px;
    text-decoration: none;
    color: #ffffff;
    height: 40px;
    line-height: 42px;
    display: block;
    text-align: center;
    border: none;
    font-size: 18px;
    font-weight: bold;
    cursor: pointer;
    outline: none;
    font-family: inherit;
    transition: all 0.2s ease;
    box-shadow: 0 0 10px rgba(59, 130, 246, 0.5);
}

.undo-button {
    background: #8b5cf6;
    /* Purple for undo */
    box-shadow: 0 0 10px rgba(139, 92, 246, 0.5);
}

.restart-button:hover {
    background-color: #2563eb;
    box-shadow: 0 0 15px rgba(59, 130, 246, 0.8);
}

.undo-button:hover {
    background-color: #7c3aed;
    box-shadow: 0 0 15px rgba(139, 92, 246, 0.8);
}

.undo-button:disabled {
    background: #94a3b8;
    cursor: not-allowed;
    box-shadow: none;
    opacity: 0.7;
}

.game-container {
    position: relative;
    padding: 15px;
    cursor: default;
    background: var(--game-container-bg);
    /* White box */
    border-radius: 6px;
    width: 500px;
    height: 500px;
    box-sizing: border-box;
    box-shadow: 0 0 30px rgba(0, 191, 255, 0.2);
    /* Soft blue glow */
}

.game-message {
    display: none;
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    background: rgba(255, 255, 255, 0.8);
    /* Lighter overlay */
    z-index: 100;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    text-align: center;
    animation: fade-in 800ms ease 1200ms;
    animation-fill-mode: both;
    color: var(--text-color);
}

.game-message.game-over {
    display: flex;
    animation: fade-in 400ms ease;
}

.game-message.game-won {
    display: flex;
    background: rgba(237, 194, 46, 0.5);
    color: #f9f6f2;
}

.game-message p {
    font-size: 60px;
    font-weight: bold;
    height: 60px;
    line-height: 60px;
    margin-bottom: 30px;
}

.game-message .lower {
    display: block;
    margin-top: 59px;
}

.game-message a {
    display: inline-block;
    background: #3b82f6;
    border-radius: 3px;
    padding: 0 20px;
    text-decoration: none;
    color: #ffffff;
    height: 40px;
    line-height: 42px;
    margin-left: 9px;
    font-weight: bold;
    cursor: pointer;
    box-shadow: 0 0 10px rgba(59, 130, 246, 0.5);
}

.grid-container {
    position: absolute;
    z-index: 1;
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-template-rows: repeat(4, 1fr);
    gap: 15px;
    width: 470px;
    height: 470px;
}

.grid-cell {
    width: 100%;
    height: 100%;
    border-radius: 3px;
    background: var(--grid-cell-bg);
    /* Light gray for cells */
}

.tile-container {
    position: absolute;
    z-index: 2;
    width: 470px;
    height: 470px;
    pointer-events: none;
}

.tile {
    position: absolute;
    width: 106.25px;
    height: 106.25px;
    border-radius: 3px;
    background: #eee4da;
    text-align: center;
    font-weight: bold;
    z-index: 10;
    font-size: 55px;
    line-height: 106.25px;
    transition: transform 100ms ease-in-out;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}

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

.tile-merged {
    z-index: 20;
    animation: pop 200ms ease 100ms;
    animation-fill-mode: backwards;
}

/* New Color Scheme: Cool Blues -> Purples -> Pinks -> Hot Pinks */

.tile-2 {
    background: #c7d2fe;
    color: #1e293b;
}

.tile-4 {
    background: #a5b4fc;
    color: #1e293b;
}

.tile-8 {
    background: #818cf8;
    color: #ffffff;
}

.tile-16 {
    background: #6366f1;
    color: #ffffff;
    box-shadow: 0 0 10px rgba(99, 102, 241, 0.4);
}

.tile-32 {
    background: #4f46e5;
    color: #ffffff;
    box-shadow: 0 0 10px rgba(79, 70, 229, 0.5);
}

.tile-64 {
    background: #4338ca;
    color: #ffffff;
    box-shadow: 0 0 15px rgba(67, 56, 202, 0.6);
}

.tile-128 {
    background: #7c3aed;
    color: #ffffff;
    font-size: 45px;
    box-shadow: 0 0 15px rgba(124, 58, 237, 0.6);
}

.tile-256 {
    background: #9333ea;
    color: #ffffff;
    font-size: 45px;
    box-shadow: 0 0 20px rgba(147, 51, 234, 0.7);
}

.tile-512 {
    background: #c026d3;
    color: #ffffff;
    font-size: 45px;
    box-shadow: 0 0 20px rgba(192, 38, 211, 0.7);
}

.tile-1024 {
    background: #db2777;
    color: #ffffff;
    font-size: 35px;
    box-shadow: 0 0 25px rgba(219, 39, 119, 0.8);
}

.tile-2048 {
    background: #e11d48;
    color: #ffffff;
    font-size: 35px;
    box-shadow: 0 0 30px rgba(225, 29, 72, 0.9);
}

.tile-super {
    background: #0f172a;
    color: #ffffff;
    font-size: 30px;
    box-shadow: 0 0 30px rgba(0, 0, 0, 1);
}

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

    100% {
        opacity: 1;
        transform: scale(1);
    }
}

@keyframes pop {
    0% {
        transform: scale(0);
    }

    50% {
        transform: scale(1.2);
    }

    100% {
        transform: scale(1);
    }
}

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

    100% {
        opacity: 1;
    }
}

.game-explanation {
    margin-top: 50px;
    color: #cbd5e1;
}

.important {
    text-transform: uppercase;
    color: #93c5fd;
}

/* Mobile Responsiveness */
@media screen and (max-width: 520px) {
    .container {
        width: 280px;
        margin: 20px auto 0;
    }

    .title {
        font-size: 27px;
        margin-top: 15px;
    }

    .scores-container {
        margin-top: 0;
        min-width: min-content;
    }

    .score-container,
    .best-container {
        padding: 5px 10px;
        font-size: 18px;
        height: 35px;
        line-height: 40px;
    }

    .score-container::after,
    .best-container::after {
        font-size: 10px;
        top: -5px;
        line-height: normal;
        padding-top: 6px;
    }

    .game-container {
        margin-top: 40px;
        position: relative;
        padding: 10px;
        width: 280px;
        height: 280px;
        box-sizing: border-box;
    }

    .grid-container {
        width: 260px;
        height: 260px;
        gap: 10px;
    }

    .grid-cell {
        width: 100%;
        /* 57.5px */
    }

    .tile {
        width: 57.5px;
        height: 57.5px;
        line-height: 57.5px;
        font-size: 35px;
    }

    .tile-128,
    .tile-256,
    .tile-512 {
        font-size: 25px;
    }

    .tile-1024,
    .tile-2048 {
        font-size: 15px;
    }

    .game-explanation {
        margin-top: 30px;
    }
}