/*
 * /mcat/assets/css/styles.css
 * Shared by index.php and reader.php. No external font dependencies.
 * Reader sidebar breakpoint matches script.js: 900px.
 * Future control hooks:
 *   <html data-theme="dark"> (or body[data-theme="dark"])
 *   #textbook-app[data-font-size="small" | "default" | "large"]
 *   .reader-tools with .reader-tool buttons
 *   .font-size-popover with .font-size-options and .font-size-option buttons
 * Selected controls use aria-pressed="true"; popovers use the hidden attribute.
 */
:root {
    color-scheme: light;
    --mcat-background: #ffffff;
    --mcat-surface: #ffffff;
    --mcat-text: #18202e;
    --mcat-reading-text: #34435a;
    --mcat-muted: #737e90;
    --mcat-border: #e3e5eb;
    --mcat-tree-line: #d1d5df;
    --mcat-hover: #f3f4f6;
    --mcat-active: #ece7ff;
    --mcat-active-text: #222333;
    --mcat-accent: #a397ff;
    --mcat-link: #5547ac;
    --mcat-focus: #6553d3;
    --mcat-error-bg: #fff1f2;
    --mcat-error-text: #982438;
    --mcat-shadow: 0 8px 24px rgb(24 32 46 / 7%);
    --mcat-popup-shadow: 0 8px 28px rgb(24 32 46 / 14%);
    --mcat-max-width: 1160px;
    --mcat-sidebar-width: 264px;
    --mcat-reading-width: 760px;
    --mcat-lesson-size: 19px;
    --mcat-toolbar-height: 56px;
    --mcat-sticky-offset: 0px;
}

html[data-theme="dark"], body[data-theme="dark"] {
    color-scheme: dark;
    --mcat-background: #151820;
    --mcat-surface: #1c202b;
    --mcat-text: #edf0f7;
    --mcat-reading-text: #d0d7e6;
    --mcat-muted: #a4aec0;
    --mcat-border: #343a49;
    --mcat-tree-line: #454b5e;
    --mcat-hover: #282e3b;
    --mcat-active: #3b335c;
    --mcat-active-text: #f0eaff;
    --mcat-accent: #b0a3ff;
    --mcat-link: #c3b6ff;
    --mcat-focus: #c3b6ff;
    --mcat-error-bg: #38232b;
    --mcat-error-text: #ffc1cd;
    --mcat-shadow: 0 8px 24px rgb(0 0 0 / 18%);
    --mcat-popup-shadow: 0 8px 28px rgb(0 0 0 / 32%);
}

*, *::before, *::after { box-sizing: border-box; }
html { scroll-padding-top: calc(var(--mcat-toolbar-height) + 24px); }
body.mcat-page {
    margin: 0;
    min-height: 100vh;
    background: var(--mcat-background);
    color: var(--mcat-text);
    font-family: Inter, "Segoe UI", Arial, sans-serif;
    font-size: 15px;
    line-height: 1.5;
    -webkit-text-size-adjust: 100%;
}
.mcat-page [hidden] { display: none !important; }
.mcat-page a { color: var(--mcat-link); text-underline-offset: 3px; }
.mcat-page button, .mcat-page select, .mcat-page input { font: inherit; }
.mcat-page button { cursor: pointer; }
.mcat-page button:disabled, .mcat-page select:disabled {
    cursor: default;
    opacity: .5;
}
.mcat-page :focus-visible { outline: 2px solid var(--mcat-focus); outline-offset: 4px; }
.mcat-page ::selection { background: var(--mcat-active); color: var(--mcat-active-text); }
.skip-link {
    position: fixed;
    z-index: 100;
    top: 10px;
    left: 12px;
    transform: translateY(-160%);
    padding: 10px 18px;
    border-radius: 6px;
    background: var(--mcat-surface);
    box-shadow: var(--mcat-popup-shadow);
}
.skip-link:focus { transform: translateY(0); }

/* Shared fallback header/footer; future includes can use these same classes. */
.site-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 20px;
    min-height: 68px;
    padding: 16px max(24px, calc((100% - var(--mcat-max-width)) / 2));
    border-bottom: 1px solid var(--mcat-border);
    background: var(--mcat-surface);
}
.site-brand { color: var(--mcat-text) !important; font-size: 23px; font-weight: 700; text-decoration: none; }
.site-section { color: var(--mcat-muted); font-size: 14px; }
.site-footer {
    border-top: 1px solid var(--mcat-border);
    padding: 24px;
    color: var(--mcat-muted);
    background: var(--mcat-background);
    text-align: center;
    font-size: 13px;
}
.site-footer p { margin: 0; }

/* Textbook listing */
.textbook-catalog {
    max-width: var(--mcat-max-width);
    margin: 0 auto;
    padding: 58px 24px 72px;
    min-height: calc(100vh - 145px);
}
.catalog-introduction { margin-bottom: 36px; }
.catalog-introduction h1 {
    margin: 0 0 12px;
    font-size: clamp(30px, 4vw, 42px);
    line-height: 1.2;
    letter-spacing: -.025em;
}
.catalog-introduction p { margin: 0; color: var(--mcat-reading-text); font-size: 18px; }
.catalog-books > h2 { margin: 0 0 24px; font-size: 20px; font-weight: 600; }
.book-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 28px; }
.book-card {
    overflow: hidden;
    border: 1px solid var(--mcat-border);
    border-radius: 12px;
    background: var(--mcat-surface);
    box-shadow: var(--mcat-shadow);
    transition: border-color .18s ease, transform .18s ease, box-shadow .18s ease;
}
.book-card-link {
    display: flex;
    flex-direction: column;
    height: 100%;
    padding: 24px;
    color: var(--mcat-text) !important;
    text-decoration: none;
}
.book-cover { display: block; width: 100%; height: 220px; margin: 0 0 22px; object-fit: contain; }
.book-card-title { margin: 0 0 10px; font-size: 21px; font-weight: 650; line-height: 1.3; }
.book-card-description { margin: 0; color: var(--mcat-reading-text); font-size: 15px; line-height: 1.65; }
.book-card:focus-within { border-color: var(--mcat-focus); }
.catalog-placeholder, .catalog-empty, .toc-placeholder { color: var(--mcat-muted); }
.catalog-placeholder { grid-column: 1 / -1; }

/* Reader toolbar and columns */
.textbook-app { min-height: calc(100vh - 145px); }
.textbook-toolbar {
    position: sticky;
    top: var(--mcat-sticky-offset);
    z-index: 20;
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 18px;
    min-height: var(--mcat-toolbar-height);
    padding: 10px max(24px, calc((100% - var(--mcat-max-width)) / 2));
    border-bottom: 1px solid var(--mcat-border);
    background: var(--mcat-background);
}
.back-to-books { color: var(--mcat-reading-text) !important; font-size: 14px; text-decoration: none; }
.textbook-toolbar-title { margin: 0 0 0 auto; color: var(--mcat-muted); font-size: 14px; }
.toc-toggle, .toc-header button, .reader-tool {
    border: 0;
    border-radius: 6px;
    background: transparent;
    color: var(--mcat-reading-text);
}
.toc-toggle { min-height: 36px; padding: 6px 10px; font-size: 14px; }
.textbook-layout {
    display: grid;
    grid-template-columns: var(--mcat-sidebar-width) minmax(0, 1fr);
    max-width: var(--mcat-max-width);
    margin: 0 auto;
    align-items: start;
}
.textbook-sidebar {
    position: sticky;
    top: calc(var(--mcat-sticky-offset) + var(--mcat-toolbar-height));
    max-height: calc(100vh - var(--mcat-sticky-offset) - var(--mcat-toolbar-height));
    max-height: calc(100dvh - var(--mcat-sticky-offset) - var(--mcat-toolbar-height));
    overflow-y: auto;
    overscroll-behavior: contain;
    scrollbar-width: thin;
    scrollbar-color: var(--mcat-tree-line) transparent;
    border-right: 1px solid var(--mcat-border);
    padding: 24px 8px 36px 16px;
    background: var(--mcat-background);
}
.book-picker { margin: 0 8px 22px 0; }
.book-picker label { display: block; margin-bottom: 8px; color: var(--mcat-muted); font-size: 12px; }
.book-picker select {
    width: 100%;
    min-height: 40px;
    padding: 8px 30px 8px 10px;
    border: 1px solid var(--mcat-border);
    border-radius: 6px;
    color: var(--mcat-text);
    background: var(--mcat-surface);
    font-weight: 600;
}
.toc-header { display: flex; flex-wrap: wrap; gap: 5px; margin: 0 8px 14px 0; }
.toc-header h2 { flex: 0 0 100%; margin: 0 0 6px; font-size: 16px; font-weight: 700; line-height: 1.4; }
.toc-header button { padding: 4px 6px; color: var(--mcat-muted); font-size: 12px; }
.table-of-contents { font-size: 14px; line-height: 1.45; }
.toc-list { list-style: none; margin: 0; padding: 0; }
.toc-list .toc-list { margin: 4px 0 8px; padding-left: 12px; border-left: 1px solid var(--mcat-tree-line); }
.toc-item { min-width: 0; margin: 2px 0; }
.toc-group > summary {
    position: relative;
    display: block;
    list-style: none;
    padding: 14px 28px 14px 12px;
    border-radius: 10px;
    cursor: pointer;
    overflow-wrap: anywhere;
}
.toc-group > summary::-webkit-details-marker { display: none; }
.toc-group > summary::after {
    content: "";
    position: absolute;
    right: 12px;
    top: 20px;
    width: 7px;
    height: 7px;
    border-right: 1.5px solid var(--mcat-muted);
    border-bottom: 1.5px solid var(--mcat-muted);
    transform: rotate(-45deg);
}
.toc-group[open] > summary::after { transform: rotate(45deg); }
.toc-lesson, .toc-label {
    display: block;
    padding: 15px 12px;
    border-radius: 10px;
    color: var(--mcat-text) !important;
    text-decoration: none;
    overflow-wrap: anywhere;
}
.toc-lesson.is-active, .toc-lesson[aria-current="page"] {
    background: var(--mcat-active);
    color: var(--mcat-active-text) !important;
    font-weight: 700;
}
.textbook-main { min-width: 0; padding: 22px 24px 64px 80px; }
.lesson-breadcrumbs { margin: 0 0 14px; color: var(--mcat-muted); font-size: 14px; letter-spacing: .02em; }
.lesson-breadcrumbs ol { display: flex; flex-wrap: wrap; gap: 7px; list-style: none; margin: 0; padding: 0; }
.lesson-breadcrumbs li { display: inline-flex; align-items: center; gap: 7px; }
.lesson-breadcrumbs li + li::before { content: ">"; color: var(--mcat-muted); }
.lesson-breadcrumbs a, .breadcrumb-group { color: var(--mcat-muted); text-decoration: none; }
.breadcrumb-group { border: 0; background: none; padding: 0; font: inherit; text-align: left; }
.lesson-breadcrumbs [aria-current="page"] { color: var(--mcat-text); }

/* Reading content */
.lesson-content {
    max-width: var(--mcat-reading-width);
    margin: 0 auto;
    color: var(--mcat-reading-text);
    font-size: var(--mcat-lesson-size);
    line-height: 1.7;
    overflow-wrap: anywhere;
    scroll-margin-top: calc(var(--mcat-toolbar-height) + 24px);
}
.lesson-content:focus { outline: none; }
.lesson-content:focus-visible { outline: 2px solid var(--mcat-focus); outline-offset: 8px; }
.lesson-content > :first-child { margin-top: 0; }
.lesson-content h1, .lesson-content h2, .lesson-content h3,
.lesson-content h4, .lesson-content h5, .lesson-content h6 { color: var(--mcat-text); line-height: 1.3; }
.lesson-content h1 { margin: 0 0 40px; font-size: 1.7em; font-weight: 700; letter-spacing: -.02em; }
.lesson-content h2 { margin: 38px 0 18px; font-size: 1.3em; font-weight: 500; }
.lesson-content h3 { margin: 30px 0 14px; font-size: 1.12em; font-weight: 650; }
.lesson-content h4 { margin: 24px 0 12px; font-size: 1em; }
.lesson-content p { margin: 0 0 20px; }
.lesson-content strong { font-weight: 700; }
.lesson-content ul, .lesson-content ol { margin: 0 0 24px; padding-left: 1.5em; }
.lesson-content li { margin: 6px 0; }
.lesson-content li > ul, .lesson-content li > ol { margin-bottom: 10px; }
.lesson-content img, .lesson-content video {
    display: block;
    max-width: 100%;
    height: auto;
    margin: 30px auto;
}
.lesson-content figure { margin: 30px 0; }
.lesson-content figure img { margin: 0 auto 20px; }
.lesson-content figcaption { margin-top: 18px; color: var(--mcat-reading-text); font-size: .95em; line-height: 1.65; }
.lesson-content iframe { display: block; max-width: 100%; border: 0; margin: 24px auto; }
.lesson-content blockquote { margin: 26px 0; padding: 12px 20px; border-left: 3px solid var(--mcat-accent); background: var(--mcat-hover); }
.lesson-content blockquote > :last-child { margin-bottom: 0; }
.lesson-content hr { margin: 32px 0; border: 0; border-top: 1px solid var(--mcat-border); }
.lesson-content table { display: block; max-width: 100%; overflow-x: auto; border-collapse: collapse; margin: 24px 0; font-size: .9em; }
.lesson-content th, .lesson-content td { border: 1px solid var(--mcat-border); padding: 10px 14px; text-align: left; vertical-align: top; }
.lesson-content th { background: var(--mcat-hover); color: var(--mcat-text); }
.lesson-content code { background: var(--mcat-hover); padding: 2px 5px; border-radius: 4px; font-size: .85em; }
.lesson-content pre { overflow-x: auto; padding: 18px; background: var(--mcat-hover); border-radius: 6px; font-size: .85em; }
.lesson-content pre code { background: transparent; padding: 0; font-size: inherit; }
.lesson-content [id] { scroll-margin-top: calc(var(--mcat-toolbar-height) + 24px); }
.lesson-navigation { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 18px; max-width: var(--mcat-reading-width); margin: 46px auto 0; padding-top: 24px; border-top: 1px solid var(--mcat-border); }
.lesson-nav-button { display: flex; flex-direction: column; gap: 6px; padding: 16px 18px; border: 1px solid var(--mcat-border); border-radius: 10px; background: var(--mcat-surface); color: var(--mcat-text); text-align: left; }
#next-lesson { text-align: right; }
.lesson-nav-direction { color: var(--mcat-muted); font-size: 12px; }
.lesson-nav-title { font-size: 14px; font-weight: 600; }
.sidebar-collapsed .textbook-layout { grid-template-columns: minmax(0, 1fr); }
.sidebar-collapsed .textbook-main { width: 100%; max-width: 880px; margin: 0 auto; padding-left: 40px; padding-right: 40px; }

/* Loading, error, and empty states */
.catalog-status, .textbook-status { margin: 0 0 16px; color: var(--mcat-muted); font-size: 13px; }
.catalog-status:empty, .textbook-status:empty { display: none; }
.catalog-error, .textbook-error, .noscript-message { margin: 0 0 24px; padding: 14px 18px; border: 1px solid var(--mcat-border); border-radius: 8px; background: var(--mcat-error-bg); color: var(--mcat-error-text); font-size: 14px; }
.lesson-content[aria-busy="true"] { min-height: 180px; }

/* Future reader controls: styles ready for markup/behavior added next. */
.reader-tools { display: flex; align-items: center; gap: 14px; position: relative; }
.reader-tool { display: inline-flex; justify-content: center; align-items: center; width: 40px; height: 36px; padding: 8px; }
.reader-tool svg { width: 20px; height: 20px; fill: none; stroke: currentColor; stroke-width: 1.5; }
.reader-tool[aria-pressed="true"] { background: var(--mcat-active); color: var(--mcat-active-text); }
.font-size-popover { position: absolute; z-index: 40; top: calc(100% + 10px); left: 0; width: 320px; max-width: calc(100vw - 32px); padding: 20px; border: 1px solid var(--mcat-tree-line); border-radius: 10px; background: var(--mcat-surface); box-shadow: var(--mcat-popup-shadow); }
.font-size-popover-title { margin: 0 24px 20px; color: var(--mcat-reading-text); text-align: center; font-size: 14px; font-weight: 400; }
.font-size-close { position: absolute; top: 14px; right: 16px; width: 28px; height: 28px; border: 0; border-radius: 4px; background: transparent; color: var(--mcat-muted); font-size: 20px; }
.font-size-options { display: flex; gap: 8px; }
.font-size-option { flex: 1; min-height: 42px; padding: 8px 10px; border: 1px solid var(--mcat-border); border-radius: 24px; color: var(--mcat-reading-text); background: var(--mcat-surface); box-shadow: 0 2px 4px rgb(0 0 0 / 18%); font-size: 14px; font-weight: 700; }
.font-size-option[aria-pressed="true"], .font-size-option.is-selected { background: var(--mcat-accent); border-color: var(--mcat-accent); color: #fff; }
#textbook-app[data-font-size="small"] { --mcat-lesson-size: 17px; }
#textbook-app[data-font-size="default"] { --mcat-lesson-size: 19px; }
#textbook-app[data-font-size="large"] { --mcat-lesson-size: 22px; }

@media (hover: hover) {
    .book-card:hover { transform: translateY(-3px); border-color: var(--mcat-accent); }
    .toc-lesson:hover:not(.is-active):not([aria-current="page"]), .toc-group > summary:hover { background: var(--mcat-hover); }
    .toc-toggle:hover:not(:disabled), .toc-header button:hover:not(:disabled), .reader-tool:hover, .font-size-close:hover { background: var(--mcat-hover); }
    .lesson-nav-button:hover:not(:disabled) { background: var(--mcat-hover); border-color: var(--mcat-tree-line); }
    .back-to-books:hover, .lesson-breadcrumbs a:hover, .breadcrumb-group:hover { text-decoration: underline; }
}

@media (max-width: 1100px) {
    :root { --mcat-sidebar-width: 250px; }
    .textbook-main { padding-left: 42px; }
    .book-grid { gap: 20px; }
}
@media (max-width: 900px) {
    .book-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
    .textbook-layout { grid-template-columns: minmax(0, 1fr); }
    .textbook-sidebar { position: relative; top: auto; max-height: 60vh; max-height: 60dvh; border-right: 0; border-bottom: 1px solid var(--mcat-border); padding: 20px 24px; }
    .textbook-main, .sidebar-collapsed .textbook-main { max-width: 840px; padding: 24px 28px 48px; margin: 0 auto; width: 100%; }
    .textbook-toolbar { gap: 10px; }
    .textbook-toolbar-title { font-size: 13px; }
    .lesson-content h1 { margin-bottom: 30px; }
}
@media (max-width: 560px) {
    :root { --mcat-lesson-size: 18px; }
    .site-header { padding: 14px 18px; min-height: 60px; }
    .site-brand { font-size: 21px; }
    .site-section { font-size: 12px; }
    .textbook-catalog { padding: 36px 18px 48px; }
    .catalog-introduction p { font-size: 16px; }
    .book-grid { grid-template-columns: minmax(0, 1fr); }
    .book-card-link { padding: 22px; }
    .book-cover { height: 200px; }
    .textbook-toolbar { padding: 10px 14px; }
    .textbook-toolbar-title { flex: 1; text-align: right; overflow-wrap: anywhere; }
    .back-to-books { font-size: 12px; }
    .toc-toggle { font-size: 12px; padding: 6px; }
    .textbook-main, .sidebar-collapsed .textbook-main { padding: 22px 20px 40px; }
    .lesson-breadcrumbs { font-size: 12px; letter-spacing: 0; }
    .lesson-content h1 { font-size: 1.5em; }
    .lesson-content h2 { font-size: 1.2em; }
    .lesson-navigation { gap: 10px; }
    .lesson-nav-button { padding: 12px; }
    .lesson-nav-title { font-size: 12px; }
    .reader-tools { gap: 6px; }
    .font-size-popover { left: 0; }
    #textbook-app[data-font-size="small"] { --mcat-lesson-size: 16px; }
    #textbook-app[data-font-size="default"] { --mcat-lesson-size: 18px; }
    #textbook-app[data-font-size="large"] { --mcat-lesson-size: 21px; }
}
@media (prefers-reduced-motion: reduce) {
    .book-card { transition: none; }
    .book-card:hover { transform: none; }
}
@media print {
    :root { color-scheme: light; --mcat-background: #fff; --mcat-text: #000; --mcat-reading-text: #000; }
    .site-header, .site-footer, .textbook-toolbar, .textbook-sidebar,
    .lesson-breadcrumbs, .lesson-navigation, .textbook-status, .textbook-error, .skip-link { display: none !important; }
    .textbook-layout { display: block; max-width: none; }
    .textbook-main, .sidebar-collapsed .textbook-main { padding: 0; max-width: none; }
    .lesson-content { max-width: none; font-size: 12pt; }
    .lesson-content h1, .lesson-content h2, .lesson-content h3 { break-after: avoid; }
    .lesson-content img, .lesson-content figure { break-inside: avoid; }
}