.scroll-top-button {
    --scroll-top-size: 56px;
    --scroll-top-radius: 18px;
    position: fixed;
    right: clamp(14px, 1vw + 12px, 28px);
    bottom: calc(env(safe-area-inset-bottom, 0px) + clamp(14px, 1vw + 12px, 28px));
    width: var(--scroll-top-size);
    height: var(--scroll-top-size);
    display: grid;
    place-items: center;
    padding: 0;
    border: 0;
    border-radius: var(--scroll-top-radius);
    background:
        radial-gradient(circle at 30% 25%, rgba(255, 255, 255, 0.28), transparent 48%),
        linear-gradient(135deg, rgba(89, 110, 245, 0.98), rgba(133, 84, 229, 0.97));
    box-shadow:
        0 18px 42px rgba(84, 99, 229, 0.34),
        0 10px 18px rgba(76, 36, 149, 0.2),
        inset 0 1px 0 rgba(255, 255, 255, 0.38);
    color: #ffffff;
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
    transform: translate3d(0, 18px, 0) scale(0.9);
    transition:
        opacity 0.28s ease,
        transform 0.28s ease,
        visibility 0.28s ease,
        box-shadow 0.28s ease,
        background 0.28s ease;
    z-index: 1040;
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
}

.scroll-top-button::before {
    content: '';
    position: absolute;
    inset: -2px;
    border-radius: calc(var(--scroll-top-radius) + 2px);
    background: linear-gradient(135deg, rgba(255, 255, 255, 0.32), rgba(255, 255, 255, 0.04));
    opacity: 0;
    transition: opacity 0.28s ease;
    z-index: 0;
}

.scroll-top-button.is-visible {
    opacity: 1;
    visibility: visible;
    pointer-events: auto;
    transform: translate3d(0, 0, 0) scale(1);
}

.scroll-top-button:hover,
.scroll-top-button:focus-visible {
    background:
        radial-gradient(circle at 30% 25%, rgba(255, 255, 255, 0.34), transparent 50%),
        linear-gradient(135deg, rgba(98, 121, 255, 1), rgba(144, 92, 240, 1));
    box-shadow:
        0 22px 52px rgba(84, 99, 229, 0.42),
        0 14px 24px rgba(76, 36, 149, 0.26),
        inset 0 1px 0 rgba(255, 255, 255, 0.42);
    transform: translate3d(0, -4px, 0) scale(1.02);
    outline: none;
}

.scroll-top-button:hover::before,
.scroll-top-button:focus-visible::before {
    opacity: 1;
}

.scroll-top-button:active {
    transform: translate3d(0, 0, 0) scale(0.97);
}

.scroll-top-button__halo,
.scroll-top-button__core,
.scroll-top-button__icon {
    position: relative;
    z-index: 1;
}

.scroll-top-button__halo {
    position: absolute;
    inset: 7px;
    border-radius: calc(var(--scroll-top-radius) - 6px);
    background: linear-gradient(180deg, rgba(255, 255, 255, 0.22), rgba(255, 255, 255, 0.06));
    opacity: 0.95;
}

.scroll-top-button__core {
    width: 100%;
    height: 100%;
    display: grid;
    place-items: center;
}

.scroll-top-button__icon {
    width: 24px;
    height: 24px;
    fill: currentColor;
    filter: drop-shadow(0 3px 8px rgba(21, 32, 94, 0.22));
}

body.modal-open .scroll-top-button {
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
    transform: translate3d(0, 14px, 0) scale(0.92);
}

@media (max-width: 991px) {
    .scroll-top-button {
        --scroll-top-size: 52px;
        --scroll-top-radius: 17px;
        right: 18px;
        bottom: calc(env(safe-area-inset-bottom, 0px) + 18px);
    }

    .scroll-top-button__icon {
        width: 22px;
        height: 22px;
    }
}

@media (max-width: 767px) {
    .scroll-top-button {
        --scroll-top-size: 48px;
        --scroll-top-radius: 16px;
        right: 14px;
        bottom: calc(env(safe-area-inset-bottom, 0px) + 14px);
    }

    .scroll-top-button__halo {
        inset: 6px;
    }

    .scroll-top-button__icon {
        width: 20px;
        height: 20px;
    }
}