website/_src/assets/css/default/nav.css

body > nav::before,
body::after {
	z-index: -1;
	content: "";
	position: absolute;
	mask-image: url("/assets/img/theme/sundae_sit-lines.png");
	mask-repeat: no-repeat;
	margin: 0;
	width: inherit;
	height: inherit;
	pointer-events: none;
}

body > nav::before {
	bottom: 0;
	left: 0;
	mask-size: 160%;
	-webkit-mask-position-x: -25px;
	-webkit-mask-position-y: 90%;
}

body::after {
	content: none;
	mask-size: 100%;
	width: 100%;
	height: 100vw;
	-webkit-mask-position-x: 0;
	-webkit-mask-position-y: bottom;
}

body > nav {
	display: flex;
	flex-direction: column;
	overflow-x: hidden;
	padding: var(--pad-l);
	position: fixed;
	width: var(--view);
	height: 100%;
	overflow-y: scroll;
	scrollbar-width: none;
	& * svg,
	li img {
		margin: 0 8px 0 8px;
		width: 20px;
		align-self: center;
	}

	& details {
		display: flex;
	}

	& ul {
		margin: var(--pad-sm);
		padding: 0;

		& li,
		button {
			padding: 0;
			align-items: center;
			margin-bottom: inherit;

			& img {
				border-radius: 100%;
			}
		}
	}

	& details {
		font-size: 1.4rem;
	}

	& a,
	button {
		display: flex;
		font-size: 1.125rem;
		width: 100%;
		font-weight: bold;
		height: 36px;
		line-height: var(--pad-xl);
	}
}

body {
	& > nav {
		gap: var(--pad-m);
		border-right-width: 1px;
		border-right-style: solid;

		& a,
		button {
			align-items: center;
			border-style: solid;
			border-width: 2px;
			border-radius: var(--round);
		}

		& details {
			border-radius: var(--round);
			font-weight: bold;
		}

		& details > summary {
			display: flex;
			justify-content: center;
			padding: 0;
			height: var(--pad-xl);
		}
		& details[open], details:not([open]) {
			border-style: solid;
			border-width: 2px;
		}
	}
}
@media screen and (max-width: 920px) {
	body > nav {
		position: initial;
		width: 100%;
		overflow: initial;
		flex-direction: row;
		justify-content: start;
		& a, button {
			line-height: initial;
		}
		& details {
			width: 100%;
			height: max-content;
		}
	}
	body > nav::before {
		content: none;
	}
}
@media screen and (max-width: 620px) {
	body > nav {
		flex-direction: column;
		justify-content: start;
		border: 0;
		width: 100%;

		& details {
			height: fit-content;
		}
	}

	body::after {
		content: "";
	}
}