2nd/10_Wiki/Topic_Programming/Topic_CSS/CSS_Box_Shadow.md

id, title, category, status, verification_status, canonical_id, aliases, duplicate_of, source_trust_level, confidence_score, created_at, updated_at, review_reason, merge_history, tags, raw_sources, applied_in, github_commit

id	title	category	status	verification_status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	created_at	updated_at	review_reason	merge_history	tags	raw_sources	applied_in	github_commit
css-box-shadow	CSS Box Shadow	Frontend	draft	conceptual		box-shadow CSS box shadow card shadow CSS inset shadow drop shadow element		B	0.9	2026-06-23	2026-06-23			css web frontend w3schools box-shadow shadows cards	https://www.w3schools.com/css/css3_shadows_box.asp

CSS Box Shadow

🎯 한 줄 통찰 (One-line insight)

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]

🧠 핵심 개념 (Core concepts)

• box-shadow shadows an element — it applies one or more shadows to an element. [S1]
• Offsets are required — the minimum form is a horizontal and a vertical offset. [S1]
• Blur radius — an optional third value blurs the shadow. [S1]
• Spread radius — an optional fourth value expands (or contracts) the shadow size. [S1]
• Color and inset — you can set the shadow color, and the inset keyword changes the shadow from an outer to an inner shadow. [S1]
• Multiple shadows — comma-separated shadows can be layered, which is how card effects are built. [S1]

🧩 추출된 패턴 (Extracted patterns)

• Offset-only pattern — box-shadow: 10px 10px;. [S1]
• Offset + color pattern — box-shadow: 10px 10px lightblue;. [S1]
• Offset + blur (+ spread) pattern — box-shadow: 10px 10px 5px 12px lightblue;. [S1]
• Inset pattern — append inset for an inner shadow. [S1]
• Card pattern — two stacked rgba() shadows to mimic a paper card. [S1]

📖 세부 내용 (Details)

Basic horizontal and vertical shadow [S1] The horizontal offset (10px) and the vertical offset (10px) are required:

div {
  box-shadow: 10px 10px;
}

Shadow with color [S1]

div {
  box-shadow: 10px 10px lightblue;
}

Blur effect (third value = blur radius) [S1]

div {
  box-shadow: 10px 10px 5px lightblue;
}

Spread radius (fourth value) [S1]

div {
  box-shadow: 10px 10px 5px 12px lightblue;
}

Inset shadow [S1] The inset keyword changes the shadow from an outer shadow to an inner shadow:

div {
  box-shadow: 10px 10px 5px lightblue inset;
}

Multiple shadows [S1] You can add as many shadows as you like, separated by commas:

div {
  box-shadow: 5px 5px 8px blue, 10px 10px 8px red, 15px 15px 8px green;
}

Cards [S1] You can use the box-shadow property to create paper-like cards:

div.card {
  width: 250px;
  box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2), 0 6px 20px 0 rgba(0, 0, 0, 0.19);
  text-align: center;
}

Shadow Properties reference [S1] 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.

🛠️ 적용 사례 (Applied in summary)

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.

💻 코드 패턴 (Code patterns)

Blur + spread shadow (language: CSS):

div {
  box-shadow: 10px 10px 5px 12px lightblue;
}

Inner (inset) shadow:

div {
  box-shadow: 10px 10px 5px lightblue inset;
}

Paper-like card:

div.card {
  width: 250px;
  box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2), 0 6px 20px 0 rgba(0, 0, 0, 0.19);
  text-align: center;
}

⚖️ 비교 및 선택 기준 (Comparison & decision criteria)

• box-shadow vs text-shadow — box-shadow shadows the whole element box; text-shadow shadows only the text glyphs. [S1]
• Outer vs inset shadow — omit inset for a drop shadow that lifts the element; add inset for a recessed/inner shadow. [S1]
• Blur only vs blur + spread — the third value blurs the shadow; the fourth (spread) value grows or shrinks the shadow's footprint. [S1]

⚖️ 모순 및 업데이트 (Contradictions & updates)

No contradictions found in the source.

✅ 검증 상태 및 신뢰도

• 상태: draft
• 검증 단계: conceptual (실제 적용 사례 발견 시 applied/validated로 승격 가능)
• 출처 신뢰도: B (W3Schools — widely used educational reference, not a primary standards body)
• 신뢰 점수: 0.90
• 중복 검사 결과: 신규 생성 (New discovery)

🔗 지식 그래프 (Knowledge Graph)

• 상위/루트: CSS Tutorial
• 관련 개념: CSS Text Shadow Effects, CSS Radial Gradients, CSS 2D Transforms
• 참조 맥락: Referenced when giving elements depth — cards, buttons, modals, and raised panels.

📚 출처 (Sources)

• [S1] W3Schools — CSS Box Shadow — https://www.w3schools.com/css/css3_shadows_box.asp

📝 변경 이력 (Change history)

• 2026-06-23: Initial draft synthesized from the W3Schools "CSS Box Shadow" page (Astra wiki-curation, P-Reinforce v3.1 format).