/* SPDX-License-Identifier: MPL-2.0 */
/* Copyright (c) 2025-2026 Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk> */
/*
 * Canonical accessible theme for casket-ssg / ddraig-ssg.
 * Target: WCAG 2.2 AAA on the engine-owned surface.
 * All text/link/UI colours are contrast-verified (see ACCESSIBILITY-CHECKLIST):
 *   light: body #1a1b26/17.1:1, muted #3a3d4d/10.7:1, link #3730a3/9.9:1
 *   dark : body #e6e8f2/15.6:1, muted #a0a4bd/7.75:1, link #b9c2ff/11.1:1
 * All >= 7:1 (AAA 1.4.6). Focus ring >= 3:1 (2.4.11/2.4.13).
 */

:root {
  --bg: #ffffff;
  --bg-soft: #f4f5f9;
  --bg-code: #eceef5;
  --fg: #1a1b26;          /* 17.09:1 on --bg */
  --fg-muted: #3a3d4d;    /* 10.74:1 on --bg (AAA for normal text) */
  --link: #3730a3;        /*  9.93:1 on --bg */
  --link-hover: #1f1b6b;
  --border: #5a5e73;      /* 4.9:1 — non-text UI, needs >=3:1 (1.4.11) */
  --focus: #3730a3;       /* focus ring, 9.93:1 vs --bg */
  --radius: 6px;
  --maxw: 70rem;
  --measure: 38rem;       /* readable line length */
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0e0f1a;
    --bg-soft: #181a2a;
    --bg-code: #1c1f33;
    --fg: #e6e8f2;        /* 15.60:1 on --bg */
    --fg-muted: #a0a4bd;  /*  7.75:1 on --bg */
    --link: #b9c2ff;      /* 11.09:1 on --bg */
    --link-hover: #dde2ff;
    --border: #8c91ad;    /* >=3:1 vs --bg */
    --focus: #b9c2ff;     /* 11.09:1 vs --bg */
  }
}

/* 1.4.12 text spacing: never clip when users override; use rem + generous line-height. */
*, *::before, *::after { box-sizing: border-box; }
html { font-size: 100%; -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  font-size: 1.0625rem;
  line-height: 1.6;            /* >= 1.5 (1.4.12) */
  color: var(--fg);
  background: var(--bg);
  overflow-wrap: break-word;   /* 1.4.10 reflow: no horizontal scroll at 320px */
}
p, li { max-width: var(--measure); }
p { margin: 0 0 1rem; }        /* paragraph spacing >= 2x font (1.4.12) */

/* 2.4.1 skip link — visible on focus, high contrast, large target. */
.skip-link {
  position: absolute; left: -9999px; top: 0;
  background: var(--link); color: #ffffff;
  padding: .75rem 1.25rem; border-radius: 0 0 var(--radius) 0;
  font-weight: 600; z-index: 100; min-height: 44px; line-height: 1.4;
}
.skip-link:focus { left: 0; }

/* 2.4.7/2.4.11/2.4.13 visible focus — thick, offset, >=3:1, never removed. */
:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: 2px;
  border-radius: 2px;
}
/* keep a focus indicator even for browsers without :focus-visible */
a:focus, button:focus, input:focus, [tabindex]:focus { outline: 3px solid var(--focus); outline-offset: 2px; }

.container { width: 100%; max-width: var(--maxw); margin-inline: auto; padding-inline: 1.25rem; }

/* Header / nav landmark */
.site-header { border-bottom: 1px solid var(--border); }
.nav { display: flex; flex-wrap: wrap; align-items: center; gap: 1rem; padding-block: .75rem; }
.brand { font-weight: 700; font-size: 1.2rem; color: var(--fg); text-decoration: none; }
.nav-links { list-style: none; display: flex; flex-wrap: wrap; gap: .5rem 1.25rem; margin: 0; padding: 0; }
/* 2.5.8/2.5.5 target size: interactive nav targets >= 44x44. */
.nav-links a, .brand { display: inline-flex; align-items: center; min-height: 44px; }

/* 1.4.1 use of colour: links are underlined, not colour-only. */
a { color: var(--link); text-decoration: underline; text-underline-offset: 2px; }
a:hover { color: var(--link-hover); }
.brand, .nav-links a { text-decoration: none; }
.nav-links a:hover, .nav-links a:focus { text-decoration: underline; }

main { display: block; }
.prose { padding-block: 2rem; }
.prose h1 { font-size: 2rem; line-height: 1.25; margin: 0 0 1rem; }
.prose h2 { font-size: 1.5rem; line-height: 1.3; margin: 2rem 0 .75rem; }
.prose h3 { font-size: 1.25rem; margin: 1.5rem 0 .5rem; }
.prose :is(h1,h2,h3,h4) { max-width: var(--measure); }

/* Code */
code { background: var(--bg-code); padding: .15em .35em; border-radius: 4px; font-size: .9em; }
pre { background: var(--bg-code); padding: 1rem; border-radius: var(--radius); overflow-x: auto; }
pre code { background: none; padding: 0; }

/* Tables — caption + scoped headers handled in markup; styling here. */
.prose table { border-collapse: collapse; width: 100%; max-width: 100%; margin: 1rem 0; }
.prose caption { text-align: left; font-weight: 600; color: var(--fg-muted); padding: .5rem 0; }
.prose th, .prose td { border: 1px solid var(--border); padding: .5rem .75rem; text-align: left; }
.prose th { background: var(--bg-soft); }

blockquote {
  margin: 1rem 0; padding: .5rem 1rem; border-left: 4px solid var(--border);
  color: var(--fg-muted); background: var(--bg-soft);
}

img { max-width: 100%; height: auto; }
hr { border: none; border-top: 1px solid var(--border); margin: 2rem 0; }

.muted { color: var(--fg-muted); }

.site-footer { border-top: 1px solid var(--border); margin-top: 3rem; padding-block: 1.5rem; color: var(--fg-muted); font-size: .95rem; }
.site-footer a { color: var(--link); }

/* 2.3.3 / user comfort: honour reduced-motion. */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: .001ms !important; animation-iteration-count: 1 !important; transition-duration: .001ms !important; scroll-behavior: auto !important; }
}

/* 1.4.10 reflow: stack nav on narrow viewports, no fixed widths. */
@media (max-width: 30rem) {
  .nav { gap: .5rem; }
  body { font-size: 1rem; }
}