/* Fonts */
@font-face {
    font-family: "Atkinson Hyperlegible";
    font-style: normal;
    font-weight: 400;
    font-display: swap;
    src: url("atkinson-hyperlegible-regular.woff2") format("woff2");
}
@font-face {
    font-family: "Atkinson Hyperlegible";
    font-style: italic;
    font-weight: 400;
    font-display: swap;
    src: url("atkinson-hyperlegible-italic.woff2") format("woff2");
}
@font-face {
    font-family: "Atkinson Hyperlegible";
    font-style: normal;
    font-weight: 700;
    font-display: swap;
    src: url("atkinson-hyperlegible-bold.woff2") format("woff2");
}
@font-face {
    font-family: "Source Code Pro";
    font-style: normal;
    font-weight: 400;
    font-display: swap;
    src: url("source-code-pro-regular.woff2") format("woff2");
}

/* Definitions */
:root {
    --color-decorate: #606060;
    --color-highlight: #f0f0f8;
    --color-page: #f8f8f8;
    --color-text: #1a1a1a;
    --color-link-unvisited: #0066ff;
    --color-link-visited: #6600cc;

    --font-prose: "Atkinson Hyperlegible", Arial, sans-serif;
    --font-code: "Source Code Pro", "Courier New", monospace;

    --len-dropdown: 200px;
    --len-half: 0.5rem;
    --len-line-height: 1.4; /* instead of standard 1.2 */
    --len-one: 1rem;
    --len-page: 60rem;
    --len-quarter: 0.25rem;
    --len-thick-double: 8px;
    --len-thick: 4px;
    --len-thin: 1px;
    --padding-left-bordered: 0.5rem;

    --size-prose: 1.1rem;
    --size-code: 0.9em;
}

/* Flex grid */

.row {
    display: flex;
    flex-flow: row wrap;
    width: 100%
}

.row > * {
  flex: 1; /* allow children to grow when space available */
}

.col-1 { flex-basis: 8.33%; }
.col-2 { flex-basis: 16.66%; }
.col-3 { flex-basis: 25%; }
.col-4 { flex-basis: 33.33%; }
.col-5 { flex-basis: 41.66%; }
.col-6 { flex-basis: 50%; }
.col-7 { flex-basis: 58.33%; }
.col-8 { flex-basis: 66.66%; }
.col-9 { flex-basis: 75%; }
.col-10 { flex-basis: 83.33%; }
.col-11 { flex-basis: 91.66%; }
.col-12 { flex-basis: 100%; }

/* Responsive breakpoints */
@media (max-width: 768px) {
    .row > * {
        flex-basis: 100% !important;
    }
}

/* Dropdown menu */

.dropdown {
    position: relative;
    display: inline-block;
}

.dropdown > a,
.dropdown > button {
    text-decoration: none;
}

/* Reset button element used as dropdown trigger */
.dropdown > button {
    background: none;
    border: none;
    padding: 0;
    font: inherit;
    color: inherit;
    cursor: pointer;
}

.dropdown-content {
    display: none;
    position: absolute;
    background-color: var(--color-highlight);
    min-width: var(--len-dropdown);
    box-shadow: 0px var(--len-thick) var(--len-thick-double) 0px rgba(0,0,0,0.2);
    z-index: 1;
    border-radius: var(--len-thick);
}

/* Reset list styling when dropdown-content is a <ul> */
ul.dropdown-content {
    list-style: none;
    padding-left: 0;
    margin-top: 0;
}

.dropdown-content a {
    padding: var(--len-half) var(--len-one);
    text-decoration: none;
    display: block;
    white-space: nowrap;
}

.dropdown-content a:hover {
    color: var(--color-link-visited);
}

.dropdown:hover .dropdown-content,
.dropdown:focus-within .dropdown-content {
    display: block;
}

/* Generic positioning */
.left {
    text-align: left;
}

.right {
    text-align: right;
}

.center {
    text-align: center;
}

/* Links */
a[href] {
    color: var(--color-link-unvisited);
}
a[href]:visited {
    color: var(--color-link-visited);
}
a[href]:hover {
    color: var(--color-link-visited);
    text-decoration: underline;
}

/* Keyboard focus indicator */
:focus-visible {
    outline: 2px solid var(--color-link-unvisited);
    outline-offset: 2px;
}

/* Skip-to-main link: hidden until focused */
.skip-link {
    position: absolute;
    top: -3rem;
    left: 0;
    background-color: var(--color-page);
    color: var(--color-link-unvisited);
    padding: var(--len-half) var(--len-one);
    z-index: 100;
    text-decoration: none;
    border: solid var(--len-thin) var(--color-link-unvisited);
}
.skip-link:focus {
    top: 0;
}

/* Quotes */
blockquote {
    border-left: solid var(--len-thick) var(--color-decorate);
    margin-left: 0px;
    padding-left: var(--len-half);
    padding-top: var(--len-half);
    padding-bottom: var(--len-half);
    margin-top: var(--len-thick);
    margin-bottom: var(--len-thick);
    background-color: var(--color-highlight);
    font-style: italic;
}

/* Headings inside blockquotes must not inherit italic */
blockquote h1,
blockquote h2,
blockquote h3 {
    font-style: normal;
}

/* Whole document */
body {
    font-family: var(--font-prose);
    font-size: var(--size-prose);
    line-height: var(--len-line-height);
    max-width: var(--len-page);
    background-color: var(--color-page);
    color: var(--color-text);
    margin: auto;
    padding-left: var(--len-half);
    padding-right: var(--len-half);
}

/* Table captions: top placement matches DOM order so sighted and AT users get the same experience */
caption {
    caption-side: top;
    text-align: left;
}

/* Code text */
code {
    font-size: var(--size-code);
    background-color: var(--color-highlight);
    padding: 0.1em 0.3em;
    border-radius: 3px;
}

/* Pre already has background; don't double-apply the inline code styling */
pre code {
    background-color: transparent;
    padding: 0;
    border-radius: 0;
}

/* Appendices */
div#appendices ol {
    list-style-type: upper-alpha;
}


/* Figures */
figure {
    text-align: center;
}
figcaption {
    text-align: left;
    max-width: 90%;
    margin: 0 auto;
}

/* Footer */
footer {
    margin-top: var(--len-half);
    border-top: solid var(--color-decorate) var(--len-thin);
    padding-top: var(--len-half);
    margin-bottom: var(--len-half);
    text-align: center;
}

/* Headings */
h1, h2, h3 {
    margin-bottom: var(--len-thick-double);
}
h2, h3 {
    margin-top: 1.5rem;
}

/* Page heading */
h1 {
    text-align: center;
}
p.subtitle {
    text-align: center;
    font-style: italic;
}

/* Images: prevent overflow on narrow viewports */
img {
    max-width: 100%;
    height: auto;
}
img.img-90 {
    width: 90%;
}

/* Navigation */
nav {
    margin-top: var(--len-half);
    border-bottom: solid var(--color-decorate) var(--len-thin);
    margin-bottom: var(--len-half);
    padding-bottom: var(--len-half);
}

/* Code block */
pre {
    background-color: var(--color-highlight);
    padding: var(--len-half);
    overflow-x: auto;
}

/* Stronger focus ring on scrollable code blocks */
pre:focus-visible {
    outline: 3px solid var(--color-link-unvisited);
    outline-offset: 2px;
}

/* Language label for screen readers and sighted users: shown when build emits data-lang */
pre[data-lang]::before {
    content: attr(data-lang);
    display: block;
    font-family: var(--font-prose);
    font-size: 0.75rem;
    color: var(--color-decorate);
    margin-bottom: var(--len-quarter);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

/* Table */
table {
  text-align: left;
  border-collapse: collapse;
  margin-bottom: var(--len-half);
}

td, th {
  padding: var(--len-half);
  border: solid var(--len-thin) var(--color-decorate);
}

tr:hover {
    background-color: var(--color-highlight);
}

thead {
    background-color: var(--color-highlight);
}

/* Lists: 1.5rem minimum indent for legibility (1rem is too tight) */
ol {
  padding-left: 1.5rem;
  margin-top: 0px;
}
ul {
  padding-left: 1.5rem;
  margin-top: 0px;
  list-style-type: disc;
}

/* Callouts */
div.callout {
    background-color: var(--color-highlight);
    border-left: solid var(--len-thick) var(--color-decorate);
    font-style: italic;
    padding-left: var(--padding-left-bordered);
}

/* Syllabus */
div.syllabus {
    background-color: var(--color-highlight);
    border-left: solid var(--len-thick) var(--color-decorate);
    font-style: italic;
    padding-left: var(--padding-left-bordered);
}

/* Definitions */
dt:not(:first-child) {
    margin-top: var(--len-quarter);
}
dt {
    font-weight: bold;
}
dd {
    margin-left: 1.5rem;
    margin-bottom: var(--len-half);
}

/* Glossary reference links: visually hidden label for screen readers */
a.gl-ref {
    position: relative;
}
a.gl-ref::after {
    content: "\00a0(glossary)";
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    clip-path: inset(50%);
    white-space: nowrap;
    border: 0;
}

/* Active nav link (current page) */
.dropdown-content a.active {
    font-weight: bold;
    text-decoration: underline;
}

/* Collapsible explanation blocks */
details.explanation {
    margin-top: var(--len-one);
}
details.explanation > summary {
    cursor: pointer;
    color: var(--color-link-unvisited);
    list-style: disclosure-closed;
    margin-left: -var(--padding-left-bordered);
    padding: var(--len-quarter) 0;
}
details.explanation[open] > summary {
    list-style: disclosure-open;
}

/* Dark mode */
@media (prefers-color-scheme: dark) {
    :root {
        --color-decorate: #606060;
        --color-highlight: #2a2a3a;
        --color-page: #1a1a1a;
        --color-text: #e8e8e8;
        --color-link-unvisited: #66aaff;
        --color-link-visited: #cc88ff;
    }
}