.coin {

    width: 32px;
    height: 32px;

    position: absolute;

    background-image: url('../images/coin.png');
    background-size: cover;
    pointer-events: none;
    transform: translate(-50%, -50%);
    will-change: transform, opacity;

}

/* 高級金屬微光 */
@keyframes coinGlow {
    0% {
        filter: brightness(1);
    }

    50% {
        filter: brightness(1.25);
    }

    100% {
        filter: brightness(1);
    }
}

#particle-layer {
    position: fixed;
    /* 跟著頁面滾動 */
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vw;
    /* ❗固定一個可視高，不要 auto */
    pointer-events: none;
    overflow: visible;
    z-index: 9999;
}

@media screen and (min-width: 768px) {
    .coin {
        width: 60px;
        height: 60px;
    }
}