/* 返回顶部按钮 */
/* 模块：返回顶部按钮 / Scroll-to-top button styling and position. */
.scroll-to-top {
	position: fixed;
	right: 0.75rem;
	bottom: 1rem;
	width: 40px;
	height: 40px;
	min-width: 40px;
	min-height: 40px;
	display: flex; /* 确保使用 flex 布局 */
	align-items: center; /* 垂直居中 */
	justify-content: center; /* 水平居中 */
	border-radius: 10px;
	border: 1px solid var(--border-color);
	background: var(--secondary-bg);
	color: var(--text-color);
	font-size: 1.2rem;
	cursor: pointer;
	box-shadow: 0 1px 2px rgba(15, 23, 42, 0.12);
	transition: background 0.18s ease, border 0.18s ease, transform 0.18s ease, opacity 0.18s ease, visibility 0.18s ease, right 240ms ease, bottom 240ms ease;
	z-index: 75;
	opacity: 0;
	visibility: hidden;
	transform: translateY(8px);
	line-height: 1;
	padding: 0;
}

.scroll-to-top.show {
	opacity: 1;
	visibility: visible;
	transform: translateY(0);
}

.scroll-to-top:hover {
	background: var(--hover-bg);
}

.scroll-to-top:active {
	transform: scale(0.95);
	background: var(--active-bg);
}

.scroll-to-top i {
	display: flex;
	align-items: center;
	justify-content: center;
	line-height: 1;
	margin: 0 !important; /* 覆盖 .item-icon 的 margin-right */
}