:root {
    --bg-col: white;
    --bg-col-alt: #F4F4F4;
    --text-col: black;
    --a-col: blue;

	--nav-bg: #e8e8e8;
    --nav-border: #ccc;
    --nav-a-col: #444;
    --nav-a-hov-col: #111;
    --nav-a-hov-bg: #d0d0d0;
    --nav-a-active-col: #1d4ed8;
    --nav-a-active-bg: #dbeafe;

	--surface: #e8e8e8;
    --surface-alt: #d8d8d8;
    --border: #ccc;
    --border-strong: #aaa;
    --muted: #555;
    --muted-light: #777;
    --kbd-bg: #e0e0e0;
    --kbd-col: #444;
    --kbd-border: #bbb;

    --review-accent: #116F33;
    --review-accent-light: #16833E;
    --review-bg-tint: #f0fdf4;
    --review-border: #4FE887;
    --review-active-bg: #dcfce7;

    --drill-accent: #7C5603;
    --drill-accent-light: #f59e0b;
    --drill-bg-tint: #fffbeb;
    --drill-border: #CEA203;
    --drill-active-bg: #fef3c7;
}

@media (prefers-color-scheme: dark) {
    :root {
		--bg-col: #1F2D33;
		--bg-col-alt: #0B0F11;
		--text-col: rgba(255, 255, 255, 87%);
		--a-col: #b8b8ff;

		--nav-bg: #171717;
		--nav-border: #444;
		--nav-a-col: #aaa;
		--nav-a-hov-col: #eee;
		--nav-a-hov-bg: #333;
		--nav-a-active-col: #60a5fa;
		--nav-a-active-bg: #1e3a5f;

		--surface: #171717;
        --surface-alt: #333;
        --border: #444;
        --border-strong: #555;
        --muted: #aaa;
        --muted-light: #888;
        --kbd-bg: #333;
        --kbd-col: #aaa;
        --kbd-border: #555;

        --review-accent: #4ade80;
        --review-accent-light: #6ee7b7;
        --review-bg-tint: #0d2818;
        --review-border: #2a5a3a;
        --review-active-bg: #14532d;

        --drill-accent: #fbbf24;
        --drill-accent-light: #fcd34d;
        --drill-bg-tint: #1c1308;
        --drill-border: #5a4a2a;
        --drill-active-bg: #78350f;
    }
}

*, *::before, *::after {
	box-sizing: border-box;
}

body {
	margin: 0;
	font-family: system-ui, -apple-system, sans-serif;
	line-height: 1.5;
	background: var(--bg-col);
	color: var(--text-col);
}

main {
	max-width: 1200px;
	margin: 0 auto;
	padding: 16px;
	padding-top: 48px;
	text-align: center;
}

footer {
	margin: 2rem auto;
	text-align: center;
}

a {
	color: var(--a-col);
}

section#info {
	text-align: justify;
	margin: 1em auto;
	max-width: 90%;
}
section#info header {
	text-align: center;
}

nav {
	display: flex;
	justify-content: space-between;
	align-items: center;
	padding: 12px 16px;
	background: var(--nav-bg);
	border-bottom: 1px solid var(--nav-border);
}

nav ul {
	list-style: none;
	display: flex;
	justify-content: center;
	gap: 24px;
	flex: 1;
}

nav ul a {
	color: var(--nav-a-col);
	text-decoration: none;
	font-weight: 500;
	padding: 8px 8px;
	border-radius: 4px;
	display: inline-block;
}

nav ul a:hover {
	color: var(--nav-a-hov-col);
	background: var(--nav-a-hov-bg);
}

nav ul a.active {
	color: var(--nav-a-active-col);
	background: var(--nav-a-active-bg);
}

.sr-only {
	position: absolute;
	width: 1px;
	height: 1px;
	padding: 0;
	margin: -1px;
	overflow: hidden;
	clip: rect(0, 0, 0, 0);
	white-space: nowrap;
	border: 0;
}