body {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-color: #f0f0f0;
    margin: 0;
}

#game-area {
    position: relative;
    width: 80vw;
    height: 80vh;
    border: 2px solid #333;
    background-color: #fff;
    display: flex;
    justify-content: center;
    align-items: center;
}

#start-btn {
    padding: 1rem 2rem;
    font-size: 1.5rem;
    cursor: pointer;
}

.hidden {
    display: none;
}

#dog {
    position: absolute;
    width: 16px;
    height: 16px;
    background-image: url('https://opengameart.org/sites/default/files/spritesheet_white.png');
    background-repeat: no-repeat;
    background-position: 0 0;
    left: 50%;
    top: 50%;
    transform: translate(-50%, -50%);
    transition: left 0.1s linear, top 0.1s linear;
    image-rendering: pixelated; /* keep it crispy */
    zoom: 4; /* make it bigger */
}

#dog.walking {
    animation: walk-cycle 0.6s steps(6) infinite;
}

#dog.left {
    transform: translate(-50%, -50%) scaleX(-1);
}

@keyframes walk-cycle {
    0% {
        background-position: 0 0;
    }
    100% {
        background-position: -96px 0;
    }
}