/* ============================================================
   reading-tools.css — 글 읽기 도구 (assets/js/single-reading.js 가 만든 요소)
   기준: docs/design-system.md «읽기 도구»
   1) 읽기 바(+ 1200px 미만 «목차» 펼침)  2) 오른쪽 목차(1200px 이상)  3) 맨 위로 버튼
   ============================================================ */

/* ------------------------------------------------------------
   1) 읽기 바 — 헤더 바로 아래, 제목을 지나면 나타난다
------------------------------------------------------------ */
.dfl-readbar {
  position: fixed;
  top: 64px; /* JS 가 실제 헤더 높이로 덮어쓴다 */
  left: 0;
  right: 0;
  z-index: 40;
  height: 40px;
  background: rgba(255, 255, 255, 0.92);
  -webkit-backdrop-filter: saturate(180%) blur(8px);
  backdrop-filter: saturate(180%) blur(8px);
  border-bottom: 1px solid var(--c-line-1);
  transform: translateY(-100%);
  opacity: 0;
  visibility: hidden;
  transition: transform var(--motion-base) ease, opacity var(--motion-base) ease, visibility 0s linear var(--motion-base);
}

.dfl-readbar.is-visible {
  transform: translateY(0);
  opacity: 1;
  visibility: visible;
  transition: transform var(--motion-base) ease, opacity var(--motion-base) ease, visibility 0s;
}

.dfl-readbar__inner {
  display: flex;
  align-items: center;
  gap: var(--sp-3);
  max-width: var(--reading-max);
  height: 100%;
  margin: 0 auto;
}

.dfl-readbar__back {
  display: inline-flex;
  align-items: center;
  gap: 2px;
  flex-shrink: 0;
  height: 100%;
  font-size: var(--fs-sm);
  font-weight: var(--fw-medium);
  color: var(--c-text-2);
  text-decoration: none;
}

.dfl-readbar__back:hover {
  color: var(--c-text-1);
}

.dfl-readbar__sep {
  flex-shrink: 0;
  width: 1px;
  height: 14px;
  background: var(--c-line-2);
}

.dfl-readbar__title {
  flex: 1;
  min-width: 0;
  overflow: hidden;
  white-space: nowrap;
  text-overflow: ellipsis;
  font-size: var(--fs-sm);
  font-weight: var(--fw-medium);
  color: var(--c-text-1);
}

/* «목차» 버튼 — 1200px 미만에서만 (넓은 화면은 오른쪽 목차가 있다) */
.dfl-readbar__toc-btn {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  flex-shrink: 0;
  height: 30px;
  padding: 0 var(--sp-3);
  border: 1px solid var(--c-line-1);
  border-radius: 999px;
  background: var(--c-bg);
  font-family: inherit;
  font-size: var(--fs-xs);
  font-weight: var(--fw-medium);
  line-height: 1;
  color: var(--c-text-2);
  cursor: pointer;
  transition: border-color var(--motion-fast) ease, color var(--motion-fast) ease;
}

/* GP 기본 button:hover/focus 의 진한 바탕을 막는다 */
.dfl-readbar__toc-btn:is(:hover, :focus, :active),
.dfl-readbar.is-toc-open .dfl-readbar__toc-btn {
  background: var(--c-bg);
  border-color: var(--c-link);
  color: var(--c-link);
}

.dfl-readbar__toc-btn:focus-visible {
  outline: 2px solid var(--c-link);
  outline-offset: 2px;
}

/* 펼침 목록 — 읽기 바 바로 아래 */
.dfl-readbar__toc {
  position: absolute;
  top: 100%;
  left: 50%;
  width: min(var(--reading-max), 100%);
  max-height: 60vh;
  overflow-y: auto;
  padding: var(--sp-2) 0;
  background: var(--c-bg);
  border: 1px solid var(--c-line-1);
  border-top: 0;
  border-radius: 0 0 var(--radius-lg) var(--radius-lg);
  box-shadow: var(--shadow-hover);
  transform: translate(-50%, -8px);
  opacity: 0;
  visibility: hidden;
  transition: transform var(--motion-base) ease, opacity var(--motion-base) ease, visibility 0s linear var(--motion-base);
}

.dfl-readbar__toc.is-open {
  transform: translate(-50%, 0);
  opacity: 1;
  visibility: visible;
  transition: transform var(--motion-base) ease, opacity var(--motion-base) ease, visibility 0s;
}

.dfl-readbar__toc ol {
  margin: 0;
  padding: 0;
  list-style: none;
}

.dfl-readbar__toc a {
  display: block;
  padding: 10px var(--sp-5) 10px calc(var(--sp-5) - 2px);
  border-left: 2px solid transparent;
  font-size: var(--fs-sm);
  line-height: var(--lh-ui);
  color: var(--c-text-2);
  text-decoration: none;
}

.dfl-readbar__toc a:hover {
  background: var(--c-bg-soft);
}

.dfl-readbar__toc a.is-active {
  border-left-color: var(--c-link);
  color: var(--c-link);
  font-weight: var(--fw-medium);
  background: var(--c-bg-summary);
}

@media (min-width: 1200px) {
  .dfl-readbar__toc-btn,
  .dfl-readbar__toc {
    display: none;
  }
}

/* 진행선 — 읽기 바 아래쪽 선 위에 겹친다 */
.dfl-readbar__progress {
  position: absolute;
  left: 0;
  right: 0;
  bottom: -1px;
  height: 2px;
}

.dfl-readbar__progress span {
  display: block;
  height: 100%;
  background: var(--c-link);
  transform: scaleX(0);
  transform-origin: 0 50%;
}

/* ------------------------------------------------------------
   2) 오른쪽 목차 — 본문(640px) 오른쪽 빈 곳에 고정
------------------------------------------------------------ */
.dfl-toc-rail {
  display: none;
}

@media (min-width: 1200px) {
  .dfl-toc-rail {
    display: block;
    position: fixed;
    top: calc(64px + 40px + var(--sp-8));
    left: calc(50% + var(--reading-max) / 2 + var(--sp-12));
    z-index: 30;
    width: 220px;
    max-height: calc(100vh - 64px - 40px - var(--sp-16));
    overflow-y: auto;
    opacity: 0;
    visibility: hidden;
    transition: opacity var(--motion-base) ease, visibility 0s linear var(--motion-base);
  }

  .dfl-toc-rail.is-visible {
    opacity: 1;
    visibility: visible;
    transition: opacity var(--motion-base) ease, visibility 0s;
  }

}

.dfl-toc-rail__title {
  margin: 0 0 var(--sp-3);
  font-size: var(--fs-xs);
  font-weight: var(--fw-bold);
  color: var(--c-text-3);
}

.dfl-toc-rail ol {
  margin: 0;
  padding: 0;
  list-style: none;
  border-left: 1px solid var(--c-line-1);
}

.dfl-toc-rail a {
  display: block;
  margin-left: -1px;
  padding: 6px 0 6px var(--sp-3);
  border-left: 2px solid transparent;
  font-size: 14px;
  line-height: var(--lh-ui);
  color: var(--c-text-3);
  text-decoration: none;
  transition: color var(--motion-fast) ease, border-color var(--motion-fast) ease;
}

.dfl-toc-rail a:hover {
  color: var(--c-text-1);
}

.dfl-toc-rail a.is-active {
  border-left-color: var(--c-link);
  color: var(--c-link);
  font-weight: var(--fw-medium);
}

/* ------------------------------------------------------------
   3) 맨 위로 버튼
------------------------------------------------------------ */
.dfl-to-top {
  position: fixed;
  right: var(--sp-8);
  bottom: var(--sp-8);
  z-index: 30;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  padding: 0;
  border: 1px solid var(--c-line-1);
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.95);
  color: var(--c-text-2);
  box-shadow: var(--shadow-hover);
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translateY(8px);
  transition: opacity var(--motion-base) ease, transform var(--motion-base) ease, visibility 0s linear var(--motion-base);
}

.dfl-to-top.is-visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
  transition: opacity var(--motion-base) ease, transform var(--motion-base) ease, visibility 0s;
}

.dfl-to-top:is(:hover, :focus, :active) {
  background: var(--c-bg);
  color: var(--c-text-1);
  border-color: var(--c-line-2);
}

.dfl-to-top:focus-visible {
  outline: 2px solid var(--c-link);
  outline-offset: 2px;
}

/* ------------------------------------------------------------
   모바일 · 태블릿
------------------------------------------------------------ */
/* 모바일·태블릿은 헤더가 고정되지 않는다(body overflow-x). 헤더가 올라가면 읽기 바가 맨 위에 붙는다 */
@media (max-width: 900px) {
  .dfl-readbar {
    top: 0;
  }
}

@media (max-width: 640px) {
  .dfl-readbar__inner {
    padding: 0 var(--gutter);
  }

  .dfl-to-top {
    right: var(--gutter);
    bottom: calc(var(--sp-6) + env(safe-area-inset-bottom));
  }
}

@media (min-width: 641px) and (max-width: 1024px) {
  .dfl-readbar__inner {
    padding: 0 var(--sp-6);
  }
}

@media (prefers-reduced-motion: reduce) {
  .dfl-readbar,
  .dfl-readbar__toc,
  .dfl-toc-rail,
  .dfl-to-top {
    transition: none;
  }
}

/* 목차 맨 위 «처음으로» — 소제목과 구분되게 아래 여백 */
.dfl-toc-rail li:first-child,
.dfl-readbar__toc li:first-child {
  margin-bottom: var(--sp-1);
}