/* OOP with JAVA — Exam Kit
   Presentation modelled on Wikipedia's Vector skin, in strict black & white.
   No colour accents, no shadows, no gradients, no border-radius. Fully offline. */

:root {
  --bg:       #ffffff;
  --fg:       #000000;
  --muted:    #54595d;
  --rule:     #a2a9b1;
  --rule-lt:  #eaecf0;
  --fill:     #f8f9fa;
  --fill-2:   #eaecf0;
  --maxw:     1220px;
  --shell:    1700px;
  --sans:     "DM Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", Arial, sans-serif;
  --serif:    "DM Sans", "Georgia", serif;
  --mono:     "JetBrains Mono", "Cascadia Code", Consolas, "Liberation Mono", monospace;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: var(--sans);
  font-size: 15px;
  font-weight: 500;          /* medium — regular reads too thin on white */
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

/* ---------------- Links ---------------- */

a { color: var(--fg); text-decoration: none; }
a:hover { text-decoration: underline; }
a:visited { color: var(--fg); }

/* ---------------- Top bar ---------------- */

.topbar {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 9px 18px;
  border-bottom: 1px solid var(--rule);
  background: var(--bg);
  font-size: 13px;
  position: sticky;
  top: 0;
  z-index: 20;
}
.topbar .home {
  font-family: var(--serif);
  font-size: 15px;
  font-weight: 400;
  letter-spacing: .01em;
}
.topbar .home:hover { text-decoration: none; border-bottom: 1px solid var(--fg); }
.topbar .crumb { color: var(--muted); }
.topbar .crumb::before { content: "/"; margin-right: 12px; color: var(--rule); }

.toc-toggle {
  margin-left: auto;
  display: none;
  font: inherit;
  font-size: 12px;
  padding: 4px 9px;
  background: var(--fill);
  color: var(--fg);
  border: 1px solid var(--rule);
  cursor: pointer;
}
.toc-toggle:hover { background: var(--fill-2); }

/* ---------------- Layout ---------------- */

.layout {
  display: flex;
  gap: 0;
  max-width: var(--shell);
  margin: 0 auto;
  padding: 0;
}

.sidebar {
  width: 268px;
  flex: 0 0 268px;
  padding: 22px 18px 60px 24px;
  border-right: 1px solid var(--rule-lt);
  font-size: 13px;
  position: sticky;
  top: 41px;
  align-self: flex-start;
  max-height: calc(100vh - 60px);
  overflow-y: auto;
}
.sidebar h2 {
  font-family: var(--sans);
  font-size: 11px;
  font-weight: 700;
  letter-spacing: .04em;
  text-transform: uppercase;
  color: var(--muted);
  margin: 0 0 9px;
  padding-bottom: 5px;
  border-bottom: 1px solid var(--rule-lt);
}
.sidebar ul { list-style: none; margin: 0; padding: 0; }
.sidebar li { margin: 0; }
.sidebar a {
  display: block;
  padding: 3px 0 3px 8px;
  line-height: 1.45;
  border-left: 2px solid transparent;
  color: var(--muted);
}
.sidebar a:hover {
  color: var(--fg);
  border-left-color: var(--rule);
  text-decoration: none;
}
.sidebar li.toc-h3 a { padding-left: 20px; font-size: 12.5px; }

.content {
  flex: 1 1 auto;
  min-width: 0;
  padding: 24px 48px 90px 40px;
}

/* ---------------- Headings (Wikipedia rules) ---------------- */

h1, h2, h3, h4 { scroll-margin-top: 56px; }

.content h1 {
  font-family: var(--serif);
  font-size: 2rem;
  font-weight: 600;
  line-height: 1.22;
  margin: 0 0 4px;
  padding-bottom: 6px;
  border-bottom: 1px solid var(--rule);
}

h2 {
  font-family: var(--serif);
  font-size: 1.5rem;
  font-weight: 600;
  line-height: 1.3;
  margin: 32px 0 12px;
  padding-bottom: 5px;
  border-bottom: 1px solid var(--rule);
}

h3 {
  font-family: var(--sans);
  font-size: 1.08rem;
  font-weight: 700;
  margin: 26px 0 8px;
}

h4 {
  font-family: var(--sans);
  font-size: .95rem;
  font-weight: 700;
  color: var(--muted);
  margin: 20px 0 6px;
}

p { margin: 0 0 .85em; }

ul, ol { margin: 0 0 .9em; padding-left: 1.7em; }
li { margin: .16em 0; }
li > ul, li > ol { margin: .2em 0; }

hr {
  border: 0;
  border-top: 1px solid var(--rule-lt);
  margin: 26px 0;
}

strong { font-weight: 700; }

/* ---------------- Tables ---------------- */

.table-wrap { overflow-x: auto; margin: .6em 0 1.2em; }

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 13.5px;
  line-height: 1.55;
  background: var(--bg);
}
th, td {
  border: 1px solid var(--rule);
  padding: 6px 9px;
  text-align: left;
  vertical-align: top;
}
th {
  background: var(--fill-2);
  font-weight: 700;
  font-size: 13px;
}
caption { caption-side: top; text-align: left; font-weight: 700; padding-bottom: 4px; }

/* ---------------- Code (light, like Wikipedia) ---------------- */

code {
  font-family: var(--mono);
  font-size: 87%;
  font-weight: 450;
  background: var(--fill);
  border: 1px solid var(--rule-lt);
  padding: 0 3px;
  color: var(--fg);
}

pre {
  font-family: var(--mono);
  font-size: 12.9px;
  font-weight: 450;
  line-height: 1.55;
  background: var(--fill);
  border: 1px solid var(--rule-lt);
  border-left: 3px solid var(--rule);
  padding: 11px 13px;
  margin: .6em 0 1.2em;
  overflow-x: auto;
  color: var(--fg);
}
pre code {
  background: none;
  border: 0;
  padding: 0;
  font-size: inherit;
}

/* ---------------- Callout boxes ---------------- */

blockquote {
  margin: .9em 0;
  padding: 9px 14px;
  border: 1px solid var(--rule);
  border-left: 3px solid var(--fg);
  background: var(--fill);
  color: var(--fg);
}
blockquote p:last-child { margin-bottom: 0; }
/* No italic faces are bundled, so emphasis uses weight, not slant. */
em, i { font-style: normal; font-weight: 700; }

/* ---------------- Pager ---------------- */

.pager {
  display: flex;
  gap: 10px;
  margin-top: 46px;
  padding-top: 14px;
  border-top: 1px solid var(--rule);
  font-size: 13.5px;
}
.pager a {
  flex: 1;
  padding: 8px 12px;
  border: 1px solid var(--rule);
  background: var(--fill);
}
.pager a:hover { background: var(--fill-2); text-decoration: none; }
.pager .dir { display: block; font-size: 11.5px; color: var(--muted); margin-bottom: 1px; }
.pager .next { text-align: right; }
.pager .spacer { flex: 1; }

/* ================= Landing page ================= */

.hero {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 30px 28px 6px;
}
.hero .kicker {
  display: block;
  font-size: 12px;
  letter-spacing: .06em;
  text-transform: uppercase;
  color: var(--muted);
  padding-bottom: 6px;
  border-bottom: 1px solid var(--rule);
  margin-bottom: 14px;
}
.hero h1 {
  font-family: var(--serif);
  font-size: 2.35rem;
  font-weight: 600;
  line-height: 1.2;
  margin: 0 0 10px;
  padding: 0;
  border: 0;
}
.hero p.lede {
  font-size: 15px;
  margin: 0 0 12px;
  max-width: 680px;
  color: var(--fg);
}
.hero .meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0;
  margin: 12px 0 4px;
  padding: 7px 0;
  border-top: 1px solid var(--rule-lt);
  border-bottom: 1px solid var(--rule-lt);
  font-size: 12.5px;
  color: var(--muted);
}
.hero .meta span { padding: 0 11px; border-left: 1px solid var(--rule-lt); }
.hero .meta span:first-child { padding-left: 0; border-left: 0; }

.search {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 16px 28px 4px;
}
.search input {
  width: 100%;
  font: inherit;
  font-size: 14px;
  padding: 7px 10px;
  border: 1px solid var(--rule);
  background: var(--bg);
  color: var(--fg);
  outline: none;
}
.search input:focus { border-color: var(--fg); }

/* Portal boxes — Wikipedia main-page style */

.cards {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 14px 28px 60px;
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
  gap: 16px;
}

.card {
  display: flex;
  flex-direction: column;
  border: 1px solid var(--rule);
  background: var(--bg);
}
a.card:hover { text-decoration: none; background: var(--fill); }

.card .num {
  display: block;
  font-family: var(--sans);
  font-size: 11px;
  font-weight: 700;
  letter-spacing: .06em;
  text-transform: uppercase;
  color: var(--muted);
  background: var(--fill-2);
  border-bottom: 1px solid var(--rule);
  padding: 5px 11px;
}

.card h3 {
  font-family: var(--serif);
  font-size: 1.16rem;
  font-weight: 600;
  margin: 0;
  padding: 11px 12px 4px;
  color: var(--fg);
}
a.card:hover h3 { text-decoration: underline; }

.card p {
  font-size: 13.5px;
  line-height: 1.55;
  color: var(--fg);
  margin: 0;
  padding: 0 12px 8px;
}

.card .tags {
  display: flex;
  flex-wrap: wrap;
  gap: 4px;
  padding: 0 12px 10px;
}
.card .tag {
  font-size: 11px;
  color: var(--muted);
  border: 1px solid var(--rule-lt);
  background: var(--fill);
  padding: 0 5px;
}

.card .foot {
  margin-top: auto;
  font-size: 12.5px;
  padding: 6px 12px;
  border-top: 1px solid var(--rule-lt);
  background: var(--fill);
  color: var(--fg);
}
a.card:hover .foot { text-decoration: underline; }

.card.feature {
  grid-column: 1 / -1;
}
.card.feature h3 { font-size: 1.4rem; padding-top: 13px; }
.card.feature p { font-size: 14px; max-width: 700px; }

.site-foot {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 16px 28px 60px;
  border-top: 1px solid var(--rule);
  font-size: 12.5px;
  color: var(--muted);
  line-height: 1.6;
}
.site-foot code { font-size: 11.5px; }

.no-results {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 0 28px 50px;
  font-size: 13.5px;
  color: var(--muted);
}

/* ---------------- Small screens ---------------- */

@media (max-width: 1280px) {
  .content { padding: 22px 34px 80px 30px; }
  .sidebar { width: 240px; flex: 0 0 240px; padding-left: 20px; }
  .hero, .search, .cards, .site-foot, .no-results { padding-left: 24px; padding-right: 24px; }
}

@media (max-width: 1080px) {
  .content { padding: 20px 26px 70px 24px; }
  .cards { grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); }
}

@media (max-width: 900px) {
  .layout { flex-direction: column; }
  .sidebar {
    position: static;
    width: auto;
    flex: none;
    max-height: none;
    border-right: 0;
    border-bottom: 1px solid var(--rule-lt);
    padding: 14px 18px 16px;
    display: none;
  }
  .sidebar.open { display: block; }
  .toc-toggle { display: inline-block; }
  .content { padding: 18px 18px 70px; max-width: 100%; }
  .topbar .crumb { display: none; }
  .cards { grid-template-columns: 1fr; }
}

@media (max-width: 640px) {
  body { font-size: 14.5px; }
  .hero { padding: 18px 16px 4px; }
  .hero h1 { font-size: 1.7rem; }
  .search { padding-left: 16px; padding-right: 16px; }
  .cards { padding-left: 16px; padding-right: 16px; }
  .content h1 { font-size: 1.55rem; }
  h2 { font-size: 1.28rem; margin-top: 26px; }
  pre { font-size: 11.8px; }
  table { font-size: 12.5px; }
  th, td { padding: 5px 7px; }
}

@media print {
  .topbar, .sidebar, .pager, .search, .toc-toggle { display: none !important; }
  .layout { display: block; }
  .content { max-width: 100%; padding: 0; }
  a { color: #000 !important; text-decoration: none; }
  pre { background: #fff; border: 1px solid #999; }
  blockquote { background: #fff; }
  h2 { page-break-after: avoid; }
  pre, table, blockquote { page-break-inside: avoid; }
}