/* ==========================================
   0) Tokens
   흑백 중립색 하나에 링크만 딥 네이비. 모서리는 6px로 통일하고 인라인 코드만 4px.
   ========================================== */
:root {
  --font-sans: "Pretendard Variable", Pretendard, -apple-system, BlinkMacSystemFont, system-ui, "Apple SD Gothic Neo", "Malgun Gothic", sans-serif;
  --font-mono: "D2Coding", ui-monospace, Consolas, monospace;

  --color-bg: #fcfcfd;
  --color-bg-sidebar: #f6f6f8;
  --color-surface: #efeff2;
  --color-border: #e2e2e7;
  --color-border-strong: #c9c9d0;
  --color-text: #17171a;
  --color-text-2: #45454d;
  --color-muted: #686871;
  --color-link: #2b4c7e;
  --color-link-hover: #1a3052;
  --color-flash: #e1e9f5;
  --color-scrim: rgb(23 23 26 / 0.32);

  --radius: 6px;
  --radius-inline: 4px;
  --sidebar-width: 17rem;
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
}

@media (prefers-color-scheme: dark) {
  :root {
    --color-bg: #131315;
    --color-bg-sidebar: #17171a;
    --color-surface: #222226;
    --color-border: #2c2c32;
    --color-border-strong: #45454d;
    --color-text: #ececef;
    --color-text-2: #c3c3ca;
    --color-muted: #9a9aa4;
    --color-link: #8eaae0;
    --color-link-hover: #b6caf0;
    --color-flash: #26324a;
    --color-scrim: rgb(0 0 0 / 0.5);
  }
}

/* ==========================================
   1) Reset + base
   ========================================== */
*, *::before, *::after { box-sizing: border-box; }

html {
  -webkit-text-size-adjust: 100%;
  scroll-padding-top: 1.5rem;
}

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.6;
  background: var(--color-bg);
  color: var(--color-text);
  word-break: keep-all;
  overflow-wrap: break-word;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

@font-face {
  font-family: "D2Coding";
  font-weight: 400;
  font-display: swap;
  src: url("https://cdn.jsdelivr.net/gh/joungkyun/font-d2coding@v1.3.2/D2Coding.woff2") format("woff2");
}

a { color: var(--color-link); }

:focus-visible {
  outline: 2px solid var(--color-link);
  outline-offset: 2px;
  border-radius: var(--radius-inline);
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
}

.skip-link {
  position: absolute;
  left: 1rem;
  top: -3rem;
  z-index: 30;
  padding: 0.5rem 0.75rem;
  background: var(--color-text);
  color: var(--color-bg);
  border-radius: var(--radius);
  text-decoration: none;
}

.skip-link:focus { top: 1rem; }

/* ==========================================
   2) Page grid: sidebar | doc | page toc
   ========================================== */
.site {
  display: grid;
  grid-template-columns: var(--sidebar-width) minmax(0, 1fr);
  min-height: 100dvh;
}

.topbar { display: none; }

.brand {
  color: var(--color-text);
  font-weight: 700;
  font-size: 1rem;
  letter-spacing: -0.01em;
  text-decoration: none;
}

/* ---------- Sidebar ---------- */
.sidebar {
  position: sticky;
  top: 0;
  height: 100dvh;
  display: flex;
  flex-direction: column;
  overflow-y: auto;
  overscroll-behavior: contain;
  background: var(--color-bg-sidebar);
  border-right: 1px solid var(--color-border);
}

.sidebar-head {
  position: sticky;
  top: 0;
  z-index: 1;
  padding: 1.375rem 1rem 0.75rem;
  background: var(--color-bg-sidebar);
}

.search {
  position: relative;
  display: block;
  margin-top: 1rem;
}

.search input {
  width: 100%;
  height: 2.25rem;
  padding: 0 2.25rem 0 0.75rem;
  font: inherit;
  font-size: 0.9375rem;
  color: var(--color-text);
  background: var(--color-bg);
  border: 1px solid var(--color-border-strong);
  border-radius: var(--radius);
  -webkit-appearance: none;
  appearance: none;
}

.search input::placeholder { color: var(--color-muted); }

.search input:focus {
  outline: 2px solid var(--color-link);
  outline-offset: -1px;
}

.search input::-webkit-search-cancel-button { display: none; }

.search kbd {
  position: absolute;
  right: 0.5rem;
  top: 50%;
  transform: translateY(-50%);
  min-width: 1.25rem;
  padding: 0 0.3rem;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  line-height: 1.25rem;
  text-align: center;
  color: var(--color-muted);
  border: 1px solid var(--color-border-strong);
  border-radius: var(--radius-inline);
  pointer-events: none;
}

.search input:focus + kbd,
.search input:not(:placeholder-shown) + kbd { display: none; }

.sidebar-nav { padding: 0.25rem 0.5rem 1.5rem; }

.sidebar-nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
}

.sidebar-nav a {
  display: block;
  padding: 0.3125rem 0.5rem;
  font-size: 0.9375rem;
  line-height: 1.45;
  color: var(--color-text-2);
  text-decoration: none;
  border-radius: var(--radius);
}

.sidebar-nav a:hover {
  color: var(--color-text);
  background: var(--color-surface);
}

.sidebar-nav a[aria-current="page"] {
  color: var(--color-text);
  font-weight: 600;
  background: var(--color-surface);
}

.nav-group-title {
  margin: 1.25rem 0.5rem 0.375rem;
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--color-muted);
}

.sidebar-foot {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin: auto 0 0;
  padding: 1rem 1.5rem 1.25rem;
  font-size: 0.875rem;
}

.sidebar-foot a {
  color: var(--color-muted);
  text-decoration: none;
}

.sidebar-foot a:hover { color: var(--color-text); }

.sidebar-foot .icon-link { display: inline-flex; }

/* ---------- Search results ---------- */
.search-results { padding: 0.25rem 0.5rem 1.5rem; }

.search-result {
  display: block;
  padding: 0.5rem 0.625rem;
  color: var(--color-text-2);
  text-decoration: none;
  border-radius: var(--radius);
}

.search-result:hover,
.search-result[aria-selected="true"] { background: var(--color-surface); }

.search-result-path {
  display: block;
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--color-text);
}

.search-result-snippet {
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
  margin-top: 0.125rem;
  font-size: 0.8125rem;
  line-height: 1.5;
  color: var(--color-muted);
}

.search-results mark {
  color: inherit;
  background: var(--color-flash);
  border-radius: 2px;
}

.search-empty {
  margin: 0.5rem 0.625rem;
  font-size: 0.875rem;
  color: var(--color-muted);
}

/* ---------- Document column ---------- */
.doc {
  display: grid;
  grid-template-columns: minmax(0, 44rem) 13rem;
  grid-template-rows: auto 1fr;
  grid-template-areas:
    "head toc"
    "body toc";
  column-gap: 4rem;
  align-content: start;
  padding: 3.5rem 3rem 0 4rem;
}

.doc-head { grid-area: head; }

.doc-body {
  grid-area: body;
  padding-bottom: 45vh; /* 마지막 헤딩도 화면 위로 올려 링크할 수 있도록 */
}

.doc-group {
  margin: 0 0 0.5rem;
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--color-muted);
}

/* ---------- Page TOC ---------- */
.page-toc {
  grid-area: toc;
  position: sticky;
  top: 3.5rem;
  align-self: start;
  max-height: calc(100dvh - 5rem);
  overflow-y: auto;
  font-size: 0.875rem;
}

.page-toc summary {
  margin-bottom: 0.625rem;
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--color-muted);
  list-style: none;
  pointer-events: none;
}

.page-toc summary::-webkit-details-marker { display: none; }

.page-toc ul {
  list-style: none;
  margin: 0;
  padding: 0;
  border-left: 1px solid var(--color-border);
}

.page-toc a {
  display: block;
  margin-left: -1px;
  padding: 0.25rem 0 0.25rem 0.875rem;
  line-height: 1.45;
  color: var(--color-muted);
  text-decoration: none;
  border-left: 1px solid transparent;
}

.page-toc .toc-l3 a { padding-left: 1.625rem; }
.page-toc .toc-l4 a { padding-left: 2.375rem; }

.page-toc a:hover { color: var(--color-text); }

.page-toc a.is-active {
  color: var(--color-text);
  border-left-color: var(--color-text);
}

/* ==========================================
   3) Prose
   ========================================== */
h1 {
  margin: 0;
  font-size: 2rem;
  font-weight: 700;
  line-height: 1.25;
  letter-spacing: -0.025em;
}

.doc-body {
  font-size: 1.0625rem;
  line-height: 1.75;
  color: var(--color-text);
}

.doc-body > :first-child { margin-top: 2rem; }

.doc-body h2,
.doc-body h3,
.doc-body h4 {
  line-height: 1.35;
  letter-spacing: -0.015em;
  font-weight: 700;
}

.doc-body h2 {
  margin: 2.5rem 0 0.75rem;
  padding-top: 2rem;
  font-size: 1.375rem;
  border-top: 1px solid var(--color-border);
}

.doc-body > h2:first-child {
  padding-top: 0;
  border-top: 0;
}

.doc-body h3 {
  margin: 2.25rem 0 0.5rem;
  font-size: 1.1875rem;
}

.doc-body h4 {
  margin: 1.75rem 0 0.5rem;
  font-size: 1.0625rem;
  color: var(--color-text-2);
}

.doc-body h2 a,
.doc-body h3 a,
.doc-body h4 a {
  color: inherit;
  text-decoration: none;
}

.doc-body h2 a::after,
.doc-body h3 a::after,
.doc-body h4 a::after {
  content: "#";
  margin-left: 0.4em;
  font-weight: 400;
  color: var(--color-muted);
  opacity: 0;
  transition: opacity 0.15s;
}

.doc-body h2 a:hover::after,
.doc-body h3 a:hover::after,
.doc-body h4 a:hover::after,
.doc-body h2 a:focus-visible::after,
.doc-body h3 a:focus-visible::after,
.doc-body h4 a:focus-visible::after { opacity: 1; }

.doc-body p { margin: 0 0 1.125rem; }

/* 본문 문장 속 링크만 밑줄. 헤딩, 홈 목록, 이전/다음 링크는 제외 */
.doc-body :is(p, li, td, th, blockquote) a:not(.feature-list a) {
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 0.2em;
  text-decoration-color: color-mix(in srgb, var(--color-link) 40%, transparent);
}

.doc-body :is(p, li, td, th, blockquote) a:not(.feature-list a):hover {
  color: var(--color-link-hover);
  text-decoration-color: currentColor;
}

.doc-body ul,
.doc-body ol {
  margin: 0 0 1.125rem;
  padding-left: 1.375rem;
}

.doc-body li { margin: 0.375rem 0; }
.doc-body li > ul,
.doc-body li > ol { margin: 0.375rem 0 0; }

.doc-body li::marker { color: var(--color-muted); }

.doc-body strong { font-weight: 650; }

.doc-body hr {
  margin: 2.5rem 0;
  border: 0;
  border-top: 1px solid var(--color-border);
}

.doc-body blockquote {
  margin: 0 0 1.125rem;
  padding: 0 0 0 1rem;
  color: var(--color-text-2);
  border-left: 2px solid var(--color-border-strong);
}

/* ---------- Code ---------- */
code, pre { font-family: var(--font-mono); }

/* 파일명 같은 코드가 하이픈에서 줄바꿈되지 않도록 한 덩어리로 둔다 */
:not(pre) > code {
  display: inline-block;
  max-width: 100%;
  padding: 0 0.35em;
  font-size: 0.875em;
  line-height: 1.5;
  vertical-align: baseline;
  background: var(--color-surface);
  border-radius: var(--radius-inline);
  overflow-wrap: anywhere;
}

.doc-body pre {
  margin: 0 0 1.25rem;
  padding: 0.875rem 1.125rem;
  font-size: 0.875rem;
  line-height: 1.65;
  background: var(--color-surface);
  border-radius: var(--radius);
  overflow-x: auto;
  tab-size: 4;
}

.doc-body pre code { word-break: normal; }

/* ---------- Tables ---------- */
.table-wrap {
  margin: 0 0 1.25rem;
  overflow-x: auto;
}

.doc-body table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9375rem;
  line-height: 1.6;
}

.doc-body th,
.doc-body td {
  padding: 0.5625rem 0.75rem;
  text-align: left;
  vertical-align: top;
}

.doc-body th:first-child,
.doc-body td:first-child { padding-left: 0; }

.doc-body th {
  font-weight: 600;
  color: var(--color-text-2);
  border-bottom: 1px solid var(--color-border-strong);
  white-space: nowrap;
}

.doc-body td { border-bottom: 1px solid var(--color-border); }

/* ---------- Media ---------- */
img, svg, video {
  max-width: 100%;
  height: auto;
}

.video-container {
  position: relative;
  width: 100%;
  margin-bottom: 1.25rem;
  aspect-ratio: 16 / 9;
  overflow: hidden;
  border-radius: var(--radius);
  background: var(--color-surface);
}

.video-container iframe {
  width: 100%;
  height: 100%;
  border: 0;
}

/* ==========================================
   4) Home: grouped feature list
   ========================================== */
.feature-groups { margin-top: 2.5rem; }

.feature-group + .feature-group { margin-top: 2.75rem; }

.doc-body .feature-group-title {
  margin: 0 0 0.25rem;
  padding: 0;
  font-size: 0.9375rem;
  font-weight: 600;
  color: var(--color-muted);
  border: 0;
  letter-spacing: 0;
}

.doc-body .feature-list {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  column-gap: 2rem;
  margin: 0;
  padding: 0;
  list-style: none;
}

.doc-body .feature-list li { margin: 0; }

.feature-list a {
  display: block;
  height: 100%;
  padding: 0.875rem 0 1rem;
  text-decoration: none;
  border-top: 1px solid var(--color-border);
}

.feature-title {
  display: block;
  font-weight: 600;
  color: var(--color-text);
  transition: color 0.15s;
}

.feature-desc {
  display: block;
  margin-top: 0.125rem;
  font-size: 0.9375rem;
  line-height: 1.55;
  color: var(--color-muted);
}

.feature-list a:hover .feature-title { color: var(--color-link); }

/* ==========================================
   5) Prev / next
   ========================================== */
.prev-next {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
  margin-top: 4rem;
}

.prev-next a {
  display: block;
  padding: 0.875rem 1rem;
  text-decoration: none;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  transition: border-color 0.15s, transform 0.1s;
}

.prev-next a:hover { border-color: var(--color-border-strong); }
.prev-next a:active { transform: translateY(1px); }

.prev-next .next {
  grid-column: 2;
  text-align: right;
}

.prev-next-label {
  display: block;
  font-size: 0.8125rem;
  color: var(--color-muted);
}

.prev-next-title {
  display: block;
  font-size: 1rem;
  font-weight: 600;
  color: var(--color-text);
}

.prev-next a:hover .prev-next-title { color: var(--color-link); }

/* ==========================================
   6) Copy-link flash feedback
   ========================================== */
.copied-flash { animation: flash-highlight 1s ease-out; }

@keyframes flash-highlight {
  0% { background-color: transparent; }
  25% { background-color: var(--color-flash); }
  100% { background-color: transparent; }
}

/* ==========================================
   7) Responsive
   ========================================== */

/* 목차가 오른쪽에 들어갈 폭이 없으면 제목 아래 접이식 상자로 내린다 */
@media (max-width: 1279px) {
  .doc {
    display: block;
    max-width: 48rem;
    padding: 3rem 3rem 0;
  }

  .page-toc {
    position: static;
    max-height: none;
    margin-top: 1.75rem;
    padding: 0.75rem 1rem;
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
  }

  .page-toc summary {
    margin: 0;
    pointer-events: auto;
    cursor: pointer;
  }

  .page-toc summary::after {
    content: "펼치기";
    float: right;
    font-weight: 400;
  }

  .page-toc[open] summary { margin-bottom: 0.625rem; }
  .page-toc[open] summary::after { content: "접기"; }
}

/* 사이드바를 서랍으로 접는다 */
@media (max-width: 899px) {
  .site { display: block; }

  .topbar {
    position: sticky;
    top: 0;
    z-index: 10;
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 3.5rem;
    padding: 0 1rem;
    background: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
  }

  .menu-button {
    padding: 0.375rem 0.75rem;
    font: inherit;
    font-size: 0.9375rem;
    color: var(--color-text);
    background: transparent;
    border: 1px solid var(--color-border-strong);
    border-radius: var(--radius);
    cursor: pointer;
  }

  .menu-button:active { transform: translateY(1px); }

  .sidebar {
    position: fixed;
    inset: 0 auto 0 0;
    z-index: 20;
    width: min(20rem, 85vw);
    height: 100dvh;
    transform: translateX(-100%);
    visibility: hidden;
    transition: transform 0.28s var(--ease-out), visibility 0s linear 0.28s;
  }

  .nav-open .sidebar {
    transform: none;
    visibility: visible;
    transition: transform 0.28s var(--ease-out), visibility 0s;
  }

  .scrim {
    position: fixed;
    inset: 0;
    z-index: 15;
    background: var(--color-scrim);
  }

  .doc { padding: 2rem 1rem 0; }

  html { scroll-padding-top: 4.5rem; }

  h1 { font-size: 1.75rem; }

  .doc-body { font-size: 1rem; }

  .doc-body .feature-list { grid-template-columns: minmax(0, 1fr); }

  .prev-next { grid-template-columns: minmax(0, 1fr); }
  .prev-next .next { grid-column: 1; }
}

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

@media (prefers-reduced-motion: no-preference) {
  html { scroll-behavior: smooth; }
}

@media print {
  .topbar, .sidebar, .page-toc, .prev-next { display: none; }
  .site, .doc { display: block; padding: 0; }
  .doc-body { padding-bottom: 0; }
}