:root {
    --crab-frame-count: 7;
    --crab-frame-width: 140px;
    --crab-frame-height: 120px;
    --crab-sprite-duration: 1.15s;
}

.crab-sprite-layer {
    position: fixed;
    inset: 0;
    pointer-events: none;
    z-index: 30;
    overflow: hidden;
}

.crab-sprite-orbit {
    position: absolute;
    left: 0;
    top: 0;
    width: var(--crab-frame-width);
    height: var(--crab-frame-height);
    will-change: transform;
}

.crab-sprite-orbit.is-moving {
    transition-property: transform;
    transition-timing-function: steps(32, end);
}

.crab-sprite-core {
    position: relative;
    width: 100%;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    filter: drop-shadow(0 14px 20px rgba(0, 0, 0, 0.24));
}

.crab-sprite-orbit.is-moving .crab-sprite-core {
    animation: crabCrawlBob 0.5s steps(3, end) infinite;
}

.crab-sprite-core::before {
    content: "";
    position: absolute;
    inset: -10px;
    border-radius: 50%;
    background: radial-gradient(circle, rgba(99, 191, 255, 0.28) 0%, rgba(99, 191, 255, 0.12) 42%, rgba(99, 191, 255, 0) 74%);
    z-index: 0;
}

.crab-sprite-core::after {
    content: "";
    position: absolute;
    left: 50%;
    bottom: -8px;
    width: 78px;
    height: 14px;
    transform: translateX(-50%);
    background: radial-gradient(ellipse at center, rgba(0, 0, 0, 0.28) 0%, rgba(0, 0, 0, 0) 72%);
    z-index: 0;
}

.crab-sprite-mask {
    position: relative;
    width: var(--crab-frame-width);
    height: var(--crab-frame-height);
    overflow: hidden;
    z-index: 1;
    -webkit-mask-image: radial-gradient(circle at center, #000 62%, transparent 100%);
    mask-image: radial-gradient(circle at center, #000 62%, transparent 100%);
    -webkit-mask-repeat: no-repeat;
    mask-repeat: no-repeat;
    -webkit-mask-size: 100% 100%;
    mask-size: 100% 100%;
}

.crab-sprite-frame {
    width: 100%;
    height: 100%;
    background-image: url('../images/xie2.png');
    background-repeat: no-repeat;
    background-position: 0 0;
    background-size: calc(var(--crab-frame-width) * var(--crab-frame-count)) var(--crab-frame-height);
    animation: crabSpriteFrames var(--crab-sprite-duration) steps(7, end) infinite;
    animation-play-state: paused;
    will-change: background-position;
}

.crab-sprite-orbit.is-moving .crab-sprite-frame {
    animation-play-state: running;
}

@keyframes crabSpriteFrames {
    from {
        background-position: 0 0;
    }

    to {
        background-position: calc(var(--crab-frame-width) * -7) 0;
    }
}

@keyframes crabCrawlBob {
    0% {
        transform: translateY(0);
    }

    50% {
        transform: translateY(-3px);
    }

    100% {
        transform: translateY(0);
    }
}

@media (max-width: 768px) {
    :root {
        --crab-frame-width: 108px;
        --crab-frame-height: 92px;
        --crab-sprite-duration: 1.25s;
    }

    .crab-sprite-layer {
        z-index: 12;
    }
}

@media (prefers-reduced-motion: reduce) {
    .crab-sprite-orbit.is-moving {
        transition: none;
    }

    .crab-sprite-frame {
        animation-duration: 1.4s;
    }
}