/* 首页「返回顶部」——固定悬浮，大气箭头指引 */

.home-back-top {
    position: fixed;
    z-index: 9980;
    box-sizing: border-box;
    right: max(14px, env(safe-area-inset-right, 0px));
    bottom: max(22px, calc(18px + env(safe-area-inset-bottom, 0px)));
    width: 52px;
    height: 52px;
    padding: 0;
    margin: 0;
    border: none;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 2px;
    background: linear-gradient(155deg, #1e3a5f 0%, #2d5a87 38%, #3d7ab5 100%);
    box-shadow:
        0 4px 14px rgba(15, 40, 70, 0.45),
        0 1px 0 rgba(255, 255, 255, 0.22) inset,
        0 -1px 0 rgba(0, 0, 0, 0.12) inset;
    color: #fff;
    opacity: 0;
    visibility: hidden;
    transform: translate3d(0, 12px, 0) scale(0.92);
    transition:
        opacity 0.35s ease,
        visibility 0.35s ease,
        transform 0.35s cubic-bezier(0.34, 1.2, 0.64, 1),
        box-shadow 0.25s ease;
    -webkit-tap-highlight-color: transparent;
    touch-action: manipulation;
}

.home-back-top.is-visible {
    opacity: 1;
    visibility: visible;
    transform: translate3d(0, 0, 0) scale(1);
}

.home-back-top:active {
    transform: translate3d(0, 0, 0) scale(0.94);
    box-shadow:
        0 2px 10px rgba(15, 40, 70, 0.35),
        0 1px 0 rgba(255, 255, 255, 0.15) inset;
}

@media (hover: hover) and (pointer: fine) {
    .home-back-top:hover {
        box-shadow:
            0 8px 22px rgba(15, 40, 70, 0.5),
            0 1px 0 rgba(255, 255, 255, 0.28) inset;
        transform: translate3d(0, -2px, 0) scale(1.02);
    }

    .home-back-top.is-visible:hover:active {
        transform: translate3d(0, 0, 0) scale(0.94);
    }
}

.home-back-top__ring {
    position: absolute;
    inset: -3px;
    border-radius: 50%;
    border: 2px solid rgba(255, 255, 255, 0.35);
    pointer-events: none;
    opacity: 0.85;
}

.home-back-top__icon {
    position: relative;
    width: 22px;
    height: 22px;
    flex-shrink: 0;
    filter: drop-shadow(0 1px 2px rgba(0, 0, 0, 0.2));
    animation: home-back-top-nudge 2.4s ease-in-out infinite;
}

@keyframes home-back-top-nudge {
    0%,
    100% {
        transform: translateY(0);
    }
    45% {
        transform: translateY(-4px);
    }
    55% {
        transform: translateY(-4px);
    }
}

.home-back-top__label {
    position: relative;
    font-size: 10px;
    font-weight: 700;
    letter-spacing: 0.12em;
    line-height: 1;
    opacity: 0.95;
    text-shadow: 0 1px 2px rgba(0, 0, 0, 0.25);
}

@media screen and (min-width: 800px) {
    .home-back-top {
        width: 56px;
        height: 56px;
        right: max(24px, env(safe-area-inset-right, 0px));
        bottom: max(28px, calc(24px + env(safe-area-inset-bottom, 0px)));
    }

    .home-back-top__icon {
        width: 24px;
        height: 24px;
    }

    .home-back-top__label {
        font-size: 11px;
    }
}