diff --git a/docs/PROJECT_STRUCTURE.md b/docs/PROJECT_STRUCTURE.md
index f5c3e05..17f2265 100644
--- a/docs/PROJECT_STRUCTURE.md
+++ b/docs/PROJECT_STRUCTURE.md
@@ -397,3 +397,127 @@ docker compose -f docker-compose.dev.yml up -d
 | `frontend/src/pages/mobile/public/Schedule.jsx` | 52KB           | 모바일 일정          |
 | `backend/services/youtube-bot.js`               | 17KB           | YouTube 수집         |
 | `backend/services/x-bot.js`                     | 16KB           | X 수집               |
+
+---
+
+## 13. 모바일 앨범 갤러리 UI
+
+### 주요 컴포넌트
+
+| 파일                                                   | 설명                          |
+| ------------------------------------------------------ | ----------------------------- |
+| `frontend/src/pages/mobile/public/AlbumGallery.jsx`    | 모바일 앨범 갤러리 (전체보기) |
+| `frontend/src/pages/mobile/public/AlbumDetail.jsx`     | 모바일 앨범 상세              |
+| `frontend/src/components/common/LightboxIndicator.jsx` | 공통 슬라이딩 점 인디케이터   |
+
+### Swiper ViewPager 스타일 라이트박스
+
+```jsx
+import { Swiper, SwiperSlide } from "swiper/react";
+import { Virtual } from "swiper/modules";
+
+<Swiper
+  modules={[Virtual]}
+  virtual
+  initialSlide={selectedIndex}
+  onSwiper={(swiper) => {
+    swiperRef.current = swiper;
+  }}
+  onSlideChange={(swiper) => setSelectedIndex(swiper.activeIndex)}
+  slidesPerView={1}
+  resistance={true}
+  resistanceRatio={0.5}
+>
+  {photos.map((photo, index) => (
+    <SwiperSlide key={index} virtualIndex={index}>
+      <img src={photo.medium_url} />
+    </SwiperSlide>
+  ))}
+</Swiper>;
+```
+
+### LightboxIndicator 사용법
+
+```jsx
+import LightboxIndicator from '../../../components/common/LightboxIndicator';
+
+// PC (기본 width 200px)
+<LightboxIndicator
+    count={photos.length}
+    currentIndex={selectedIndex}
+    goToIndex={(i) => swiperRef.current?.slideTo(i)}
+/>
+
+// 모바일 (width 120px로 축소)
+<LightboxIndicator
+    count={photos.length}
+    currentIndex={selectedIndex}
+    goToIndex={(i) => swiperRef.current?.slideTo(i)}
+    width={120}
+/>
+```
+
+### 2열 지그재그 Masonry 그리드
+
+```jsx
+// 1,3,5번 → 왼쪽 열 / 2,4,6번 → 오른쪽 열
+const distributePhotos = () => {
+  const leftColumn = [];
+  const rightColumn = [];
+  photos.forEach((photo, index) => {
+    if (index % 2 === 0) leftColumn.push({ ...photo, originalIndex: index });
+    else rightColumn.push({ ...photo, originalIndex: index });
+  });
+  return { leftColumn, rightColumn };
+};
+```
+
+### 뒤로가기 처리 패턴
+
+```jsx
+// 모달/라이트박스 열 때 히스토리 추가
+const openLightbox = useCallback((images, index, options = {}) => {
+  setLightbox({ open: true, images, index, ...options });
+  window.history.pushState({ lightbox: true }, "");
+}, []);
+
+// popstate 이벤트로 닫기
+useEffect(() => {
+  const handlePopState = () => {
+    if (showModal) setShowModal(false);
+    else if (lightbox.open) setLightbox((prev) => ({ ...prev, open: false }));
+  };
+  window.addEventListener("popstate", handlePopState);
+  return () => window.removeEventListener("popstate", handlePopState);
+}, [showModal, lightbox.open]);
+
+// X 버튼도 history.back() 호출
+<button onClick={() => window.history.back()}>
+  <X size={24} />
+</button>;
+```
+
+### 바텀시트 (정보 표시)
+
+```jsx
+<motion.div
+  initial={{ y: "100%" }}
+  animate={{ y: 0 }}
+  exit={{ y: "100%" }}
+  drag="y"
+  dragConstraints={{ top: 0, bottom: 0 }}
+  dragElastic={{ top: 0, bottom: 0.5 }}
+  onDragEnd={(_, info) => {
+    if (info.offset.y > 100 || info.velocity.y > 300) {
+      window.history.back();
+    }
+  }}
+  className="bg-zinc-900 rounded-t-3xl"
+>
+  {/* 드래그 핸들 */}
+  <div className="flex justify-center pt-3 pb-2">
+    <div className="w-10 h-1 bg-zinc-600 rounded-full" />
+  </div>
+  {/* 내용 */}
+</motion.div>
+```