:root{
--back-to-top-size: 44px;
--back-to-top-bg: rgba(17, 24, 39, 0.9);
--back-to-top-bg-light: rgba(255, 255, 255, 0.95);
--back-to-top-color: var(--md-accent-fg-color, #f59e0b);
--back-to-top-shadow: 0 10px 15px -3px rgba(0,0,0,.1), 0 4px 6px -4px rgba(0,0,0,.1);
--back-to-top-border: rgba(255, 255, 255, 0.2);
}
/* Button base */
.back-to-top {
position: fixed;
left: 50%;
right: auto;
bottom: calc(16px + env(safe-area-inset-bottom));
width: var(--back-to-top-size);
height: var(--back-to-top-size);
display: inline-flex;
align-items: center;
justify-content: center;
border-radius: 9999px;
background: var(--back-to-top-bg);
color: var(--back-to-top-color) !important;
border: 1px solid var(--back-to-top-border);
box-shadow: var(--back-to-top-shadow);
backdrop-filter: saturate(180%) blur(8px);
-webkit-backdrop-filter: saturate(180%) blur(8px);
opacity: 0;
visibility: hidden;
transform: translate(-50%, 10px) scale(0.98);
transition: opacity .2s ease, transform .2s ease, visibility .2s ease, background .2s ease, color .2s ease;
z-index: 13001; /* above header (12000) */
pointer-events: auto;
will-change: opacity, transform;
}
/* Visible state */
.back-to-top.visible {
opacity: 1;
visibility: visible;
transform: translate(-50%, 0) scale(1);
}
/* Icon */
.back-to-top svg {
width: 26px;
height: 26px;
display: block;
color: var(--back-to-top-color) !important;
}
/* Text icon styling (preferred) */
.back-to-top .back-to-top-icon {
font-size: 22px;
line-height: 1;
display: inline-block;
color: var(--back-to-top-color);
font-weight: 900;
text-shadow: 0 2px 6px rgba(245, 158, 11, 0.45);
}
/* Hide SVG fallback by default to avoid double icon */
.back-to-top .back-to-top-svg-fallback { display: none; }
/* Hover/active */
.back-to-top:hover {
background: rgba(31, 41, 55, 0.8);
}
.back-to-top:active {
transform: translateY(0) scale(0.98);
}
/* Focus ring */
.back-to-top:focus {
outline: none;
box-shadow: 0 0 0 3px rgba(245, 158, 11, 0.35), var(--back-to-top-shadow);
}
/* Respect reduced motion */
@media (prefers-reduced-motion: reduce) {
.back-to-top {
transition: none;
}
}
/* Light/Dark scheme awareness via Material attribute */
html[data-md-color-scheme="default"] .back-to-top {
background: var(--back-to-top-bg-light);
color: var(--back-to-top-color);
border-color: rgba(17, 24, 39, 0.08);
}
html[data-md-color-scheme="slate"] .back-to-top {
background: var(--back-to-top-bg);
color: var(--back-to-top-color);
border-color: rgba(255, 255, 255, 0.12);
}
/* Ensure inner shapes also use currentColor in both themes */
.back-to-top svg path,
.back-to-top svg line,
.back-to-top svg polyline,
.back-to-top svg rect {
stroke: currentColor;
stroke-width: 2.25;
}
/* Filled caret uses theme accent via currentColor */
.back-to-top svg .filled {
fill: currentColor !important;
stroke: none !important;
}
