/* Colour scheme */
:root {
	--b: #ededed;
	--f: #121212;
	--a: #0000ff;
}
.darkinv {}
@media only screen and (prefers-color-scheme: dark) {
	:root {
		--b: #121212;
		--f: #ededed;
		--a: #ffff00;
	}
	.darkinv {filter: invert(100%);}
}

/* Basic elements */
/* See also https://github.com/necolas/normalize.css/blob/master/normalize.css */
html {
	line-height: 1.5;
	-webkit-text-size-adjust: none;
	text-size-adjust: none;
}
hr {
	box-sizing: content-box;
	height: 0;
	overflow: visible;
}
body {
	background: #ededed;
	background: var(--b);
	color: #121212;
	color: var(--f);

	max-width: 80ch;
	margin: auto;
	padding: 1rem 0;

	font-family: sans-serif;
}
h1, h2, h3 {text-align: center;}
h1 {font-size: 2.0rem;}
h2 {font-size: 1.6rem;}
h3 {font-size: 1.2rem;}
a {
	background-color: transparent;
	text-decoration: none;
	color: #0000ff;
	color: var(--a);
}
img {
	border-style: none;
	display: block;
	max-width: 100%;
	height: auto;
	margin: auto;
}
table {margin: auto;}
td {padding: 0 1.5rem;}
/*code, pre {
	font-family: monospace, monospace;
	font-size: 1em;
}*/
b, strong {font-weight: bolder;}

/* Header and footer */
.nav {
	height: 3rem;
	font-size: 2.4rem;
}
.navl, .footl {
	float: left;
	text-align: left;
}
.navr, .footr {
	float: right;
	text-align: right;
}
@media only screen and (max-width: 72ch) {
	.navl, .footl, .footr {width: 100%;}
	.navr {
		width: 100%;
		font-size: 1.8rem;
	}
}
.noha a:link, .noha a:visited {
	color: #121212;
	color: var(--f);
}
.noha a:hover, .noha a:focus, .noha a:active {
	color: #0000ff;
	color: var(--a);
}

/* IE-compatible collapsible proofs */
div.proof {
	display: block;
	border: dotted;
	padding: 0.25rem 0.5rem;
}
label.proof {
	color: #0000ff;
	color: var(--a);
	cursor: pointer;
}
.proof-hidden {display: none;}
input.proof {display: none;}
input.proof:checked + label {display: none;}
input.proof:checked + label + .proof-hidden {display: block;}
.proof-starts + p {margin-top: 0;}