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-variables-in-media-queries
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title: "CSS Variables in Media Queries"
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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: ["CSS custom properties media queries", "responsive CSS variables", "override variable in @media", "--fontsize media query", "variable breakpoints"]
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duplicate_of: ""
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source_trust_level: "B"
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confidence_score: 0.88
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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", "css-variables", "media-queries", "responsive"]
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raw_sources: ["https://www.w3schools.com/css/css3_variables_mediaqueries.asp"]
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applied_in: []
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github_commit: ""
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---
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# [[CSS Variables in Media Queries]]
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## 🎯 한 줄 통찰 (One-line insight)
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CSS variables can be reassigned inside `@media` rules, so a single `var()`-driven design responds to screen size simply by overriding the variable's value at a breakpoint. [S1]
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## 🧠 핵심 개념 (Core concepts)
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- **Media queries enable responsive styling** — they allow you to set different styles for different devices/screen sizes. [S1]
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- **Variables are overridable per breakpoint** — you can change a variable's value inside a media query, and every rule that reads it via `var()` updates automatically. [S1]
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- **Local vs. root scope** — a variable defined on `.container` (e.g. `--fontsize`) can be overridden for `.container` inside a media query, while a variable on `:root` (e.g. `--primary-bg-color`) can be overridden globally inside the same query. [S1]
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## 🧩 추출된 패턴 (Extracted patterns)
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- **Breakpoint override pattern** — redefine the variable inside `@media screen and (min-width: …)` to switch its value above that width. [S1]
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- **Single-property responsiveness** — changing `--fontsize` from `20px` to `40px` at `min-width: 450px` makes the font-size responsive without touching the `font-size` declaration itself. [S1]
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- **Multi-variable override** — multiple variables (a local `--fontsize` on `.container` and a global `--primary-bg-color` on `:root`) can be overridden together within one media query. [S1]
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## 📖 세부 내용 (Details)
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Media queries let you set different style values for different devices. The page demonstrates overriding a CSS variable's value based on screen width: the `--fontsize` variable is `20px` on small screens and becomes `40px` on screens that are `450px` or wider. [S1]
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**Example 1 — override a single variable at a breakpoint** [S1]
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```css
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:root {
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--primary-bg-color: #1e90ff;
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--primary-color: #ffffff;
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}
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body {
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background-color: var(--primary-bg-color);
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}
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.container {
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--fontsize: 20px;
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color: var(--primary-bg-color);
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background-color: var(--primary-color);
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padding: 15px;
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font-size: var(--fontsize);
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}
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.container h2 {
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border-bottom: 2px solid var(--primary-bg-color);
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}
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@media screen and (min-width: 450px) {
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.container {
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--fontsize: 40px;
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}
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}
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```
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**Example 2 — override multiple variables in the media query** [S1]
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A second example modifies multiple variables inside the media query, additionally changing `--primary-bg-color` from the blue hex value to `lightblue` at the larger breakpoint: [S1]
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```css
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:root {
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--primary-bg-color: #1e90ff;
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--primary-color: #ffffff;
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}
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body {
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background-color: var(--primary-bg-color);
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}
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.container {
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--fontsize: 20px;
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color: var(--primary-bg-color);
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background-color: var(--primary-color);
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padding: 15px;
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font-size: var(--fontsize);
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}
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.container h2 {
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border-bottom: 2px solid var(--primary-bg-color);
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}
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@media screen and (min-width: 450px) {
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.container {
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--fontsize: 40px;
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}
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:root {
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--primary-bg-color: lightblue;
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}
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}
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```
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**CSS `var()` function reference** [S1]
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| Function | Description |
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|----------|-------------|
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| `var()` | Inserts the value of a CSS variable |
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## 🛠️ 적용 사례 (Applied in summary)
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The page's applied examples are a responsive card (`.container`): font size scales from 20px to 40px at the 450px breakpoint (Example 1), and in Example 2 the global background color also flips to `lightblue` above that width. No external project/commit applications found in the source.
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## 💻 코드 패턴 (Code patterns)
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Override a variable at a breakpoint (language: CSS):
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```css
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.container {
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--fontsize: 20px;
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font-size: var(--fontsize);
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}
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@media screen and (min-width: 450px) {
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.container {
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--fontsize: 40px;
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}
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}
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```
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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:** 0.88
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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 Variables]], [[CSS Variables and JavaScript]], [[CSS Media Queries]], [[CSS @property]]
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- **참조 맥락:** Referenced when building responsive designs whose tokens (font sizes, colors) change at viewport breakpoints via custom properties.
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## 📚 출처 (Sources)
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- [S1] W3Schools — CSS Variables in Media Queries — https://www.w3schools.com/css/css3_variables_mediaqueries.asp
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## 📝 변경 이력 (Change history)
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- 2026-06-23: Initial draft synthesized from the W3Schools "CSS Variables in Media Queries" page (Astra wiki-curation, P-Reinforce v3.1 format).
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