/* Deliberately plain. This is a page people reach when something has gone
   wrong, often through a screen reader or at a large text size, so it favours
   legibility and structure over decoration. No JavaScript, no web fonts,
   nothing that can fail to load. */

:root {
    color-scheme: light dark;

    --bg: #ffffff;
    --text: #1a1a1a;
    --muted: #52525b;
    --link: #0b4fa8;
    --rule: #d4d4d8;
    --accent-bg: #f4f4f5;
}

@media (prefers-color-scheme: dark) {
    :root {
        --bg: #14141a;
        --text: #ececf1;
        --muted: #a1a1aa;
        /* Lightened for contrast against the dark background — the light-mode
           blue falls below 4.5:1 here. */
        --link: #7fb2ff;
        --rule: #34343d;
        --accent-bg: #1e1e26;
    }
}

body {
    background: var(--bg);
    color: var(--text);
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, sans-serif;
    /* Unitless line-height so it scales with the user's font size rather than
       being locked to the base size. */
    line-height: 1.6;
    font-size: 1.0625rem;
    margin: 0 auto;
    max-width: 42rem;
    padding: 1.5rem 1.25rem 4rem;
}

/* Visible only once focused, so a keyboard user can jump the navigation
   without it cluttering the page for everyone else. */
.skip {
    position: absolute;
    left: -9999px;
}
.skip:focus {
    position: static;
    display: inline-block;
    margin-bottom: 1rem;
    padding: 0.5rem 0.75rem;
    background: var(--accent-bg);
    border-radius: 0.375rem;
}

h1 {
    font-size: 1.875rem;
    line-height: 1.25;
    margin: 0 0 0.25rem;
}

h2 {
    font-size: 1.3125rem;
    margin: 2.5rem 0 0.75rem;
    padding-bottom: 0.375rem;
    border-bottom: 1px solid var(--rule);
}

h3 {
    font-size: 1.0625rem;
    margin: 1.75rem 0 0.375rem;
}

p, ul {
    margin: 0 0 1rem;
}

ul {
    padding-left: 1.375rem;
}

li {
    margin-bottom: 0.375rem;
}

.tagline {
    color: var(--muted);
    margin-bottom: 1.5rem;
}

.lede {
    font-size: 1.125rem;
}

.updated {
    color: var(--muted);
    font-size: 0.9375rem;
}

.contact-email {
    background: var(--accent-bg);
    border-radius: 0.5rem;
    padding: 0.875rem 1rem;
    /* Long addresses shouldn't overflow on a narrow screen. */
    overflow-wrap: anywhere;
}

nav ul {
    display: flex;
    gap: 1.25rem;
    list-style: none;
    margin: 0 0 1rem;
    padding: 0 0 0.75rem;
    border-bottom: 1px solid var(--rule);
}

nav li {
    margin: 0;
}

/* The current page is marked with aria-current for screen readers; this is the
   matching visual cue, so both audiences get the same information. */
nav [aria-current="page"] {
    font-weight: 600;
    text-decoration: none;
    color: var(--text);
}

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

/* Never remove the underline from body links: colour alone fails for anyone
   who can't distinguish it. */
a:hover {
    text-decoration: none;
}

:focus-visible {
    outline: 3px solid var(--link);
    outline-offset: 2px;
    border-radius: 2px;
}

footer {
    margin-top: 3.5rem;
    padding-top: 1rem;
    border-top: 1px solid var(--rule);
    color: var(--muted);
    font-size: 0.9375rem;
}

footer a {
    margin-left: 0.5rem;
}