:root[data-theme="light"] {
  --bg: #ffffff;
  --bg-elev: #f6f6f6;
  --bg-mute: #ececec;
  --ink: #0a0a0a;
  --ink-soft: #3a3a3a;
  --ink-mute: #6a6a6a;
  --line: #d8d8d8;
  --line-strong: #0a0a0a;
  --invert: #0a0a0a;
  --invert-ink: #ffffff;
  --code-bg: #111111;
  --code-ink: #f4f4f4;
  --code-muted: #9a9a9a;
  --shadow: 0 12px 40px rgba(0, 0, 0, 0.08);
  --ok-bg: #0a0a0a;
  --ok-ink: #ffffff;
  --bad-bg: #e8e8e8;
  --bad-ink: #0a0a0a;
  --overlay: rgba(10, 10, 10, 0.45);
}

:root[data-theme="dark"] {
  --bg: #0a0a0a;
  --bg-elev: #141414;
  --bg-mute: #1c1c1c;
  --ink: #f5f5f5;
  --ink-soft: #d0d0d0;
  --ink-mute: #8a8a8a;
  --line: #2a2a2a;
  --line-strong: #f5f5f5;
  --invert: #f5f5f5;
  --invert-ink: #0a0a0a;
  --code-bg: #000000;
  --code-ink: #f4f4f4;
  --code-muted: #8a8a8a;
  --shadow: 0 16px 50px rgba(0, 0, 0, 0.55);
  --ok-bg: #f5f5f5;
  --ok-ink: #0a0a0a;
  --bad-bg: #2a2a2a;
  --bad-ink: #f5f5f5;
  --overlay: rgba(0, 0, 0, 0.65);
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
  min-height: 100%;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: "IBM Plex Sans", "IBM Plex Sans Arabic", system-ui, sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.65;
  font-size: 16px;
  overflow-x: hidden;
}

img,
svg,
iframe {
  max-width: 100%;
}

button,
input,
textarea,
select {
  font: inherit;
  color: inherit;
}

a {
  color: inherit;
}

code,
pre,
.mono,
kbd,
.editor,
.codeblock,
.built {
  font-family: "IBM Plex Mono", ui-monospace, monospace;
  direction: ltr;
  unicode-bidi: isolate;
  text-align: left;
}

.skip {
  position: absolute;
  inset-inline-start: -999px;
  top: 0;
  background: var(--invert);
  color: var(--invert-ink);
  padding: 0.6rem 1rem;
  z-index: 80;
}

.skip:focus {
  inset-inline-start: 1rem;
  top: 1rem;
}

.app {
  min-height: 100dvh;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 40;
  display: flex;
  align-items: center;
  gap: 0.75rem;
  min-height: 60px;
  padding: 0.5rem 0.85rem;
  padding-top: calc(0.5rem + env(safe-area-inset-top));
  background: var(--invert);
  color: var(--invert-ink);
  border-bottom: 1px solid var(--invert);
}

.icon-btn {
  appearance: none;
  border: 1px solid transparent;
  background: transparent;
  color: inherit;
  width: 44px;
  height: 44px;
  min-width: 44px;
  display: grid;
  place-items: center;
  cursor: pointer;
  border-radius: 10px;
}

.icon-btn:hover,
.icon-btn:focus-visible {
  background: color-mix(in srgb, var(--invert-ink) 12%, transparent);
  outline: none;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  text-decoration: none;
  min-width: 0;
}

.brand-mark {
  width: 32px;
  height: 32px;
  flex-shrink: 0;
  background: var(--invert-ink);
  color: var(--invert);
  display: grid;
  place-items: center;
  font-weight: 700;
  border-radius: 7px;
  letter-spacing: -0.04em;
}

.brand-text {
  display: flex;
  flex-direction: column;
  line-height: 1.15;
  min-width: 0;
}

.brand-text strong {
  font-size: 0.95rem;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.brand-text span {
  font-size: 0.72rem;
  opacity: 0.7;
}

.search {
  flex: 1;
  min-width: 0;
  position: relative;
  display: none;
}

.search input {
  width: 100%;
  height: 42px;
  border-radius: 999px;
  border: 1px solid color-mix(in srgb, var(--invert-ink) 22%, transparent);
  background: color-mix(in srgb, var(--invert-ink) 8%, transparent);
  color: var(--invert-ink);
  padding: 0 1rem 0 2.4rem;
  outline: none;
}

html[dir="rtl"] .search input {
  padding: 0 2.4rem 0 1rem;
}

.search svg {
  position: absolute;
  inset-inline-start: 0.85rem;
  top: 50%;
  transform: translateY(-50%);
  opacity: 0.7;
  pointer-events: none;
}

.search-results {
  display: none;
  position: absolute;
  top: calc(100% + 0.4rem);
  inset-inline: 0;
  background: var(--bg);
  color: var(--ink);
  border: 1px solid var(--line);
  border-radius: 12px;
  box-shadow: var(--shadow);
  max-height: 320px;
  overflow: auto;
  z-index: 50;
}

.search-results.open {
  display: block;
}

.search-results a {
  display: block;
  padding: 0.7rem 0.9rem;
  text-decoration: none;
  border-bottom: 1px solid var(--line);
}

.search-results a:hover {
  background: var(--bg-elev);
}

.top-actions {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  margin-inline-start: auto;
}

.lang-switch {
  display: flex;
  border: 1px solid color-mix(in srgb, var(--invert-ink) 25%, transparent);
  border-radius: 999px;
  overflow: hidden;
}

.lang-switch button {
  appearance: none;
  border: 0;
  background: transparent;
  color: inherit;
  padding: 0.35rem 0.55rem;
  min-height: 36px;
  cursor: pointer;
  font-size: 0.75rem;
  font-weight: 600;
}

.lang-switch button[aria-pressed="true"] {
  background: var(--invert-ink);
  color: var(--invert);
}

.layout {
  display: flex;
  min-height: calc(100dvh - 60px);
}

.sidebar {
  position: fixed;
  inset-block: 0;
  inset-inline-start: 0;
  width: min(86vw, 300px);
  background: var(--bg-elev);
  border-inline-end: 1px solid var(--line);
  padding: calc(70px + env(safe-area-inset-top)) 0 5.5rem;
  overflow: auto;
  transform: translateX(-105%);
  transition: transform 0.22s ease;
  z-index: 30;
}

html[dir="rtl"] .sidebar {
  transform: translateX(105%);
}

.sidebar.open {
  transform: translateX(0);
}

.backdrop {
  display: none;
  position: fixed;
  inset: 0;
  background: var(--overlay);
  z-index: 25;
}

.backdrop.open {
  display: block;
}

.nav-group {
  padding: 0.4rem 0.85rem 0.85rem;
}

.nav-label {
  font-size: 0.72rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-mute);
  padding: 0.75rem 0.55rem 0.35rem;
  font-weight: 600;
}

.nav-link {
  display: flex;
  align-items: center;
  gap: 0.55rem;
  padding: 0.62rem 0.7rem;
  border-radius: 10px;
  text-decoration: none;
  color: var(--ink-soft);
  min-height: 44px;
}

.nav-link .num {
  width: 1.5rem;
  font-variant-numeric: tabular-nums;
  color: var(--ink-mute);
  font-size: 0.8rem;
}

.nav-link.active,
.nav-link:hover {
  background: var(--invert);
  color: var(--invert-ink);
}

.nav-link.active .num,
.nav-link:hover .num {
  color: inherit;
}

.main {
  flex: 1;
  min-width: 0;
  padding: 1rem 1rem 8.5rem;
}

.page {
  max-width: 920px;
  margin: 0 auto;
}

.crumb {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
  color: var(--ink-mute);
  font-size: 0.85rem;
  margin-bottom: 0.75rem;
}

.kicker {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.75rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  font-weight: 700;
  color: var(--ink-mute);
}

h1,
h2,
h3 {
  line-height: 1.2;
  letter-spacing: -0.03em;
  margin: 0 0 0.65rem;
}

h1 {
  font-size: clamp(1.7rem, 5vw, 2.6rem);
}

h2 {
  font-size: clamp(1.2rem, 3vw, 1.55rem);
  margin-top: 2rem;
}

h3 {
  font-size: 1.05rem;
  margin-top: 1.4rem;
}

.lead {
  font-size: 1.08rem;
  color: var(--ink-soft);
  margin-top: 0;
}

.grid-cards {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.85rem;
  margin: 1.2rem 0 1.6rem;
}

.card {
  background: var(--bg-elev);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 1rem 1.05rem;
  text-decoration: none;
  color: inherit;
  display: block;
  min-height: 44px;
}

.card:hover {
  border-color: var(--ink);
}

.card h3 {
  margin: 0.2rem 0 0.35rem;
}

.card p {
  margin: 0;
  color: var(--ink-soft);
  font-size: 0.95rem;
}

.stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.6rem;
  margin: 1rem 0 1.5rem;
}

.stat {
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 0.85rem;
  background: var(--bg-elev);
  text-align: center;
}

.stat b {
  display: block;
  font-size: 1.35rem;
}

.stat span {
  font-size: 0.75rem;
  color: var(--ink-mute);
}

.ul {
  padding-inline-start: 1.15rem;
}

.ul li {
  margin: 0.35rem 0;
}

.callout {
  border: 1px solid var(--line-strong);
  border-radius: 14px;
  padding: 0.9rem 1rem;
  margin: 1rem 0;
  background: var(--bg-elev);
}

.callout strong {
  display: block;
  margin-bottom: 0.2rem;
}

.table-wrap {
  overflow-x: auto;
  margin: 1rem 0 1.4rem;
  border: 1px solid var(--line);
  border-radius: 12px;
  -webkit-overflow-scrolling: touch;
}

table {
  width: 100%;
  border-collapse: collapse;
  min-width: 460px;
  font-size: 0.94rem;
}

th,
td {
  text-align: start;
  padding: 0.7rem 0.8rem;
  border-bottom: 1px solid var(--line);
  vertical-align: top;
}

th {
  background: var(--bg-mute);
  font-weight: 600;
}

tr:last-child td {
  border-bottom: 0;
}

code.inline {
  background: var(--bg-mute);
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: 0.05rem 0.35rem;
  font-size: 0.9em;
  direction: ltr;
  unicode-bidi: isolate;
  display: inline-block;
}

.example {
  margin: 1.2rem 0 1.6rem;
  border: 1px solid var(--line);
  border-radius: 16px;
  overflow: hidden;
  background: var(--bg);
  scroll-margin-bottom: 6rem;
}

.example-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.6rem;
  padding: 0.7rem 0.85rem;
  background: var(--bg-elev);
  border-bottom: 1px solid var(--line);
  font-weight: 600;
}

.btn {
  appearance: none;
  border: 1px solid var(--invert);
  background: var(--invert);
  color: var(--invert-ink);
  border-radius: 999px;
  padding: 0.45rem 0.9rem;
  min-height: 40px;
  cursor: pointer;
  font-weight: 600;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.35rem;
  white-space: nowrap;
}

.btn.ghost {
  background: transparent;
  color: var(--ink);
  border-color: var(--line-strong);
}

.btn:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

.example-split {
  display: grid;
  grid-template-columns: 1fr;
}

.preview {
  padding: 1rem;
  background: #fff;
  color: #111;
  min-height: 88px;
}

:root[data-theme="dark"] .preview {
  background: #f7f7f7;
  color: #111;
}

.codeblock {
  margin: 0;
  padding: 0.95rem 1rem;
  background: var(--code-bg);
  color: var(--code-ink);
  overflow-x: auto;
  font-size: 0.86rem;
  line-height: 1.55;
  -webkit-overflow-scrolling: touch;
}

.figure {
  margin: 1.2rem 0;
  border: 1px dashed var(--line-strong);
  border-radius: 16px;
  padding: 1rem;
  background: var(--bg-elev);
}

.figure-title {
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--ink-mute);
  font-weight: 700;
  margin-bottom: 0.8rem;
}

.anatomy {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  align-items: stretch;
}

.piece {
  flex: 1;
  min-width: 120px;
  border: 1px solid var(--ink);
  border-radius: 12px;
  padding: 0.75rem;
  text-align: center;
  background: var(--bg);
}

.piece b {
  display: block;
  font-family: "IBM Plex Mono", monospace;
  font-size: 1.05rem;
}

.piece span {
  display: block;
  font-size: 0.78rem;
  color: var(--ink-mute);
  margin-top: 0.25rem;
}

.structure {
  border: 2px solid var(--ink);
  border-radius: 8px;
  overflow: hidden;
  font-size: 0.9rem;
}

.structure .row {
  padding: 0.55rem 0.75rem;
  border-bottom: 1px solid var(--line);
}

.structure .row:last-child {
  border-bottom: 0;
}

.structure .html {
  background: var(--bg);
  font-weight: 700;
}

.structure .head {
  margin: 0.4rem;
  background: var(--bg-mute);
  border: 1px solid var(--line);
}

.structure .body {
  margin: 0.4rem;
  min-height: 90px;
  background: var(--bg);
  border: 1px solid var(--ink);
}

.browser {
  border: 1px solid var(--ink);
  border-radius: 12px;
  overflow: hidden;
  background: var(--bg);
}

.browser-bar {
  display: flex;
  gap: 0.45rem;
  align-items: center;
  padding: 0.45rem 0.6rem;
  background: var(--bg-mute);
  border-bottom: 1px solid var(--line);
}

.dots {
  display: flex;
  gap: 0.25rem;
}

.dots i {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--ink);
  display: block;
  opacity: 0.35;
}

.tab {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  background: var(--bg);
  border: 1px solid var(--line);
  border-radius: 8px 8px 0 0;
  padding: 0.28rem 0.55rem;
  font-size: 0.82rem;
}

.fav {
  width: 14px;
  height: 14px;
  background: var(--ink);
  color: var(--bg);
  display: grid;
  place-items: center;
  font-size: 0.55rem;
  font-weight: 800;
  border-radius: 3px;
}

.pager {
  display: flex;
  justify-content: space-between;
  gap: 0.6rem;
  margin-top: 2rem;
  flex-wrap: wrap;
}

.pager a {
  flex: 1;
  min-width: min(100%, 180px);
}

.sticky-next {
  position: fixed;
  inset-inline: 0;
  bottom: 0;
  z-index: 20;
  display: flex;
  gap: 0.5rem;
  padding: 0.65rem 0.85rem calc(0.65rem + env(safe-area-inset-bottom));
  background: var(--bg);
  border-top: 1px solid var(--line);
}

.sticky-next .btn {
  flex: 1;
}

.quiz-q,
.ex-box,
.summary-card {
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 1rem;
  background: var(--bg-elev);
  margin: 0.85rem 0;
}

.options {
  display: grid;
  gap: 0.5rem;
}

.opt {
  text-align: start;
  border: 1px solid var(--line);
  background: var(--bg);
  border-radius: 12px;
  padding: 0.8rem 0.9rem;
  min-height: 48px;
  cursor: pointer;
}

.opt.selected {
  border-color: var(--ink);
  box-shadow: inset 3px 0 0 var(--ink);
}

html[dir="rtl"] .opt.selected {
  box-shadow: inset -3px 0 0 var(--ink);
}

.opt.correct {
  background: var(--ok-bg);
  color: var(--ok-ink);
  border-color: var(--ok-bg);
}

.opt.wrong {
  background: var(--bad-bg);
  color: var(--bad-ink);
}

.editor-wrap {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.7rem;
}

textarea.editor {
  width: 100%;
  min-height: 220px;
  border-radius: 12px;
  border: 1px solid var(--line);
  background: var(--code-bg);
  color: var(--code-ink);
  padding: 0.85rem;
  resize: vertical;
  line-height: 1.5;
  font-size: 16px;
}

.frame {
  width: 100%;
  min-height: 180px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: #fff;
}

.feedback {
  margin-top: 0.7rem;
  padding: 0.75rem 0.85rem;
  border-radius: 12px;
  border: 1px solid var(--line);
}

.feedback.ok {
  background: var(--ok-bg);
  color: var(--ok-ink);
  border-color: var(--ok-bg);
}

.feedback.bad {
  background: var(--bad-bg);
  color: var(--bad-ink);
}

.ex-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin: 0.8rem 0 1rem;
}

.chip {
  min-width: 40px;
  min-height: 40px;
  border-radius: 10px;
  border: 1px solid var(--line);
  background: var(--bg);
  cursor: pointer;
  font-weight: 600;
}

.chip.done {
  background: var(--invert);
  color: var(--invert-ink);
}

.chip.current {
  outline: 2px solid var(--ink);
  outline-offset: 1px;
}

.progress-bar {
  height: 8px;
  background: var(--bg-mute);
  border-radius: 99px;
  overflow: hidden;
  margin: 0.6rem 0 1rem;
}

.progress-bar span {
  display: block;
  height: 100%;
  background: var(--invert);
  width: 0;
}

.tabs {
  display: flex;
  gap: 0.4rem;
  overflow-x: auto;
  padding-bottom: 0.3rem;
  margin: 0.6rem 0 1rem;
}

.tabs button {
  border: 1px solid var(--line);
  background: var(--bg);
  border-radius: 999px;
  padding: 0.45rem 0.8rem;
  min-height: 40px;
  cursor: pointer;
  white-space: nowrap;
}

.tabs button.active {
  background: var(--invert);
  color: var(--invert-ink);
  border-color: var(--invert);
}

#mindmap {
  width: 100%;
  height: min(72vh, 640px);
  border: 1px solid var(--line);
  border-radius: 16px;
  background: var(--bg-elev);
  touch-action: none;
}

.flip-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.7rem;
}

.flip {
  min-height: 120px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: var(--bg-elev);
  padding: 1rem;
  cursor: pointer;
  position: relative;
}

.flip .back {
  display: none;
}

.flip.open .front {
  display: none;
}

.flip.open .back {
  display: block;
}

.flip.open {
  background: var(--invert);
  color: var(--invert-ink);
  border-color: var(--invert);
}

.builder {
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
  margin: 0.7rem 0;
}

.tag-btn {
  border: 1px dashed var(--ink);
  background: var(--bg);
  border-radius: 8px;
  padding: 0.45rem 0.65rem;
  cursor: pointer;
  font-family: "IBM Plex Mono", monospace;
  min-height: 44px;
}

.built {
  min-height: 52px;
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 0.6rem;
  background: var(--code-bg);
  color: var(--code-ink);
  font-family: "IBM Plex Mono", monospace;
  word-break: break-word;
}

.blank-input {
  display: inline-block;
  width: 7.2rem;
  max-width: 42vw;
  border: 0;
  border-bottom: 2px solid var(--ink);
  background: transparent;
  text-align: center;
  margin: 0 0.15rem;
  font-family: "IBM Plex Mono", monospace;
}

.hero-visual {
  display: grid;
  gap: 0.8rem;
  margin: 1rem 0 1.5rem;
}

.modal[hidden] {
  display: none !important;
}

.modal {
  display: none;
  position: fixed;
  inset: 0;
  z-index: 60;
  background: var(--bg);
  padding: 0.7rem;
  padding-top: calc(0.7rem + env(safe-area-inset-top));
  overflow: auto;
}

.modal.open {
  display: block;
}

.modal-head {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 0.6rem;
  margin-bottom: 0.7rem;
}

.home-search {
  display: block;
  margin: 0.4rem 0 1rem;
}

.home-search {
  position: relative;
}

.home-search input {
  width: 100%;
  height: 46px;
  border-radius: 12px;
  border: 1px solid var(--line);
  background: var(--bg-elev);
  padding: 0 0.9rem;
}

.home-results {
  position: static;
  margin-top: 0.4rem;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
}

@media (min-width: 880px) {
  .search,
  .home-search {
    display: block;
  }

  .home-search {
    display: none;
  }

  .menu-btn {
    display: none;
  }

  .sidebar {
    position: sticky;
    top: 60px;
    height: calc(100dvh - 60px);
    transform: none;
    flex-shrink: 0;
    width: 280px;
    padding-top: 0.8rem;
  }

  html[dir="rtl"] .sidebar {
    transform: none;
  }

  .backdrop {
    display: none !important;
  }

  .main {
    padding: 1.6rem 2rem 4rem;
  }

  .example-split {
    grid-template-columns: 1fr 1fr;
  }

  .example-split .codeblock {
    border-inline-start: 1px solid #222;
  }

  .editor-wrap {
    grid-template-columns: 1fr 1fr;
  }

  .grid-cards,
  .flip-grid {
    grid-template-columns: 1fr 1fr;
  }

  .sticky-next {
    display: none;
  }

  .hero-visual {
    grid-template-columns: 1.1fr 0.9fr;
    align-items: center;
  }
}

@media (min-width: 1100px) {
  .grid-cards {
    grid-template-columns: 1fr 1fr 1fr;
  }
}

@media (max-width: 879px) {
  .brand-text span {
    display: none;
  }

  .lang-switch button {
    padding: 0.35rem 0.42rem;
  }
}

html[dir="rtl"] .editor,
html[dir="rtl"] .codeblock,
html[dir="rtl"] .codeblock code,
html[dir="rtl"] .built,
html[dir="rtl"] .ltr-iso {
  direction: ltr !important;
  unicode-bidi: isolate;
  text-align: left !important;
}

@media (prefers-reduced-motion: reduce) {
  * {
    scroll-behavior: auto !important;
    transition: none !important;
  }
}