docs(10_Wiki): W3Schools 위키화 — HTML/CSS/JavaScript(core)
W3Schools 튜토리얼을 P-Reinforce v3.1 포맷으로 위키화(영어 본문, 한/영 섹션 헤더). - Topic_HTML: 59문서 (튜토리얼+예제, 레퍼런스/메타 제외) - Topic_CSS: 190문서 (메인 + Advanced/Flexbox/Grid/RWD 전체) - Topic_JavaScript: 120문서 (코어 언어; Temporal/DOM상세/BOM/WebAPI/AJAX/jQuery/Graphics 등은 후속) 각 폴더 00_INDEX.md(MOC) 포함. 코드 verbatim, 미확인분은 "Not found in source" 표기. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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id: css-box-shadow
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title: "CSS Box Shadow"
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category: "Frontend"
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status: "draft"
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verification_status: "conceptual"
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canonical_id: ""
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aliases: ["box-shadow", "CSS box shadow", "card shadow CSS", "inset shadow", "drop shadow element"]
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duplicate_of: ""
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source_trust_level: "B"
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confidence_score: 0.9
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created_at: 2026-06-23
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updated_at: 2026-06-23
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review_reason: ""
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merge_history: []
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tags: ["css", "web", "frontend", "w3schools", "box-shadow", "shadows", "cards"]
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raw_sources: ["https://www.w3schools.com/css/css3_shadows_box.asp"]
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applied_in: []
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github_commit: ""
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---
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# [[CSS Box Shadow]]
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## 🎯 한 줄 통찰 (One-line insight)
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The `box-shadow` property attaches one or more shadows to an element using horizontal/vertical offsets, with optional blur radius, spread radius, color, and an `inset` keyword — commonly used to make elements look like raised cards. [S1]
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## 🧠 핵심 개념 (Core concepts)
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- **`box-shadow` shadows an element** — it applies one or more shadows to an element. [S1]
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- **Offsets are required** — the minimum form is a horizontal and a vertical offset. [S1]
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- **Blur radius** — an optional third value blurs the shadow. [S1]
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- **Spread radius** — an optional fourth value expands (or contracts) the shadow size. [S1]
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- **Color and `inset`** — you can set the shadow color, and the `inset` keyword changes the shadow from an outer to an inner shadow. [S1]
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- **Multiple shadows** — comma-separated shadows can be layered, which is how card effects are built. [S1]
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## 🧩 추출된 패턴 (Extracted patterns)
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- **Offset-only pattern** — `box-shadow: 10px 10px;`. [S1]
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- **Offset + color pattern** — `box-shadow: 10px 10px lightblue;`. [S1]
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- **Offset + blur (+ spread) pattern** — `box-shadow: 10px 10px 5px 12px lightblue;`. [S1]
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- **Inset pattern** — append `inset` for an inner shadow. [S1]
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- **Card pattern** — two stacked `rgba()` shadows to mimic a paper card. [S1]
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## 📖 세부 내용 (Details)
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**Basic horizontal and vertical shadow** [S1]
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The horizontal offset (10px) and the vertical offset (10px) are required:
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```css
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div {
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box-shadow: 10px 10px;
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}
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```
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**Shadow with color** [S1]
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```css
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div {
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box-shadow: 10px 10px lightblue;
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}
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```
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**Blur effect (third value = blur radius)** [S1]
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```css
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div {
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box-shadow: 10px 10px 5px lightblue;
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}
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```
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**Spread radius (fourth value)** [S1]
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```css
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div {
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box-shadow: 10px 10px 5px 12px lightblue;
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}
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```
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**Inset shadow** [S1]
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The `inset` keyword changes the shadow from an outer shadow to an inner shadow:
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```css
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div {
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box-shadow: 10px 10px 5px lightblue inset;
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}
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```
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**Multiple shadows** [S1]
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You can add as many shadows as you like, separated by commas:
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```css
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div {
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box-shadow: 5px 5px 8px blue, 10px 10px 8px red, 15px 15px 8px green;
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}
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```
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**Cards** [S1]
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You can use the `box-shadow` property to create paper-like cards:
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```css
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div.card {
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width: 250px;
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box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2), 0 6px 20px 0 rgba(0, 0, 0, 0.19);
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text-align: center;
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}
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```
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**Shadow Properties reference** [S1]
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The page includes a table listing the shadow properties `box-shadow` (adds shadows to elements) and `text-shadow` (adds shadows to text), with their descriptions.
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## 🛠️ 적용 사례 (Applied in summary)
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The page's own demonstrations (`div` elements showing offset, color, blur, spread, inset, multiple shadows, and the `div.card` paper-card effect) serve as the applied examples. No external project/commit applications found in the source.
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## 💻 코드 패턴 (Code patterns)
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Blur + spread shadow (language: CSS):
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```css
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div {
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box-shadow: 10px 10px 5px 12px lightblue;
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}
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```
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Inner (inset) shadow:
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```css
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div {
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box-shadow: 10px 10px 5px lightblue inset;
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}
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```
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Paper-like card:
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```css
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div.card {
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width: 250px;
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box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2), 0 6px 20px 0 rgba(0, 0, 0, 0.19);
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text-align: center;
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}
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```
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## ⚖️ 비교 및 선택 기준 (Comparison & decision criteria)
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- **`box-shadow` vs `text-shadow`** — `box-shadow` shadows the whole element box; `text-shadow` shadows only the text glyphs. [S1]
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- **Outer vs inset shadow** — omit `inset` for a drop shadow that lifts the element; add `inset` for a recessed/inner shadow. [S1]
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- **Blur only vs blur + spread** — the third value blurs the shadow; the fourth (spread) value grows or shrinks the shadow's footprint. [S1]
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## ⚖️ 모순 및 업데이트 (Contradictions & updates)
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No contradictions found in the source.
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## ✅ 검증 상태 및 신뢰도
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- **상태:** draft
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- **검증 단계:** conceptual (실제 적용 사례 발견 시 applied/validated로 승격 가능)
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- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
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- **신뢰 점수:** 0.90
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- **중복 검사 결과:** 신규 생성 (New discovery)
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## 🔗 지식 그래프 (Knowledge Graph)
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- **상위/루트:** [[CSS Tutorial]]
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- **관련 개념:** [[CSS Text Shadow Effects]], [[CSS Radial Gradients]], [[CSS 2D Transforms]]
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- **참조 맥락:** Referenced when giving elements depth — cards, buttons, modals, and raised panels.
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## 📚 출처 (Sources)
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- [S1] W3Schools — CSS Box Shadow — https://www.w3schools.com/css/css3_shadows_box.asp
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## 📝 변경 이력 (Change history)
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- 2026-06-23: Initial draft synthesized from the W3Schools "CSS Box Shadow" page (Astra wiki-curation, P-Reinforce v3.1 format).
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