CSS 아키텍처와 방법론

<button class="btn btn--large btn--primary">클릭</button>
<button class="btn btn--small btn--secondary">취소</button>

/* 구조 (재사용 가능한 기본 버튼 스타일) */
.btn {
    display: inline-block;
    padding: 10px 20px;
    border: none;
    cursor: pointer;
    text-align: center;
    border-radius: 5px;
}
.btn--large {
    padding: 15px 30px;
    font-size: 1.2em;
}
.btn--small {
    padding: 8px 15px;
    font-size: 0.9em;
}

/* 스킨 (색상 테마) */
.btn--primary {
    background-color: #3498db;
    color: white;
}
.btn--secondary {
    background-color: #2ecc71;
    color: white;
}

/* 나쁜 예시 (컨테이너 종속적) */
.sidebar .menu-list li a {
    color: blue;
}

/* 좋은 예시 (재사용 가능한 컴포넌트) */
.menu-item {
    display: block;
    padding: 10px;
}
.menu-item-link {
    color: blue;
}

<div class="card">
    <img class="card__image" src="image.jpg" alt="제품 이미지">
    <h3 class="card__title">제품명</h3>
    <p class="card__description">제품 설명입니다.</p>
    <button class="card__button card__button--primary">구매</button>
</div>

<div class="card card--featured">
    <img class="card__image" src="image2.jpg" alt="특별 제품 이미지">
    <h3 class="card__title">특별 제품</h3>
    <p class="card__description">특별 할인 중!</p>
    <button class="card__button card__button--secondary">자세히 보기</button>
</div>

/* Block */
.card {
    border: 1px solid #ccc;
    padding: 15px;
    border-radius: 8px;
    background-color: white;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
    width: 300px;
}

/* Element */
.card__image {
    max-width: 100%;
    height: auto;
    display: block;
    margin-bottom: 10px;
}
.card__title {
    font-size: 1.5em;
    color: #333;
    margin-bottom: 5px;
}
.card__description {
    font-size: 0.9em;
    color: #666;
    margin-bottom: 15px;
}
.card__button {
    padding: 8px 15px;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-size: 1em;
}

/* Modifier (Block level) */
.card--featured {
    border-color: #f1c40f;
    box-shadow: 0 5px 15px rgba(0,0,0,0.2);
}

/* Modifier (Element level) */
.card__button--primary {
    background-color: #3498db;
    color: white;
}
.card__button--secondary {
    background-color: #2ecc71;
    color: white;
}

<!DOCTYPE html>
<html lang="ko">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>CSS 아키텍처 실습</title>
    <link rel="stylesheet" href="css/style.css">
</head>
<body>
    <header class="l-header">
        <h1 class="l-header__title">블로그</h1>
        <nav class="main-nav">
            <ul class="main-nav__list">
                <li class="main-nav__item"><a href="#" class="main-nav__link is-active" aria-current="page">홈</a></li>
                <li class="main-nav__item"><a href="#" class="main-nav__link">카테고리</a></li>
                <li class="main-nav__item"><a href="#" class="main-nav__link">문의</a></li>
            </ul>
        </nav>
    </header>

    <main class="l-main-content">
        <section class="l-section">
            <h2 class="l-section__title">최신 게시물</h2>
            <div class="post-grid">
                <article class="post-card">
                    <div class="post-card__content">
                        <h3 class="post-card__title">CSS 아키텍처의 중요성</h3>
                        <p class="post-card__excerpt">대규모 프로젝트에서 CSS를 효과적으로 관리하는 방법론을 알아봅니다.</p>
                        <a href="#" class="post-card__read-more button button--primary">더 읽기</a>
                    </div>
                </article>

                <article class="post-card post-card--featured is-new">
                    <div class="post-card__content">
                        <h3 class="post-card__title">Flexbox와 Grid 비교 분석</h3>
                        <p class="post-card__excerpt">언제 Flexbox를 쓰고, 언제 Grid를 써야 할까?</p>
                        <a href="#" class="post-card__read-more button button--secondary">더 읽기</a>
                    </div>
                </article>

                <article class="post-card">
                    <div class="post-card__content">
                        <h3 class="post-card__title">자바스크립트 비동기 프로그래밍</h3>
                        <p class="post-card__excerpt">콜백, Promise, Async/Await 완벽 이해하기.</p>
                        <a href="#" class="post-card__read-more button button--primary">더 읽기</a>
                    </div>
                </article>
            </div>
        </section>
    </main>

    <footer class="l-footer">
        <p class="l-footer__text">&copy; 2026 CSS 아키텍처 실습. 모든 권리 보유.</p>
    </footer>
</body>
</html>

/* style.css */

@import url('_base.css');
@import url('_layout.css');
@import url('_module.css');
@import url('_state.css');

/* CSS 변수는 :root에 정의하는 것이 일반적이며, 이곳이나 _base.css에 포함 가능 */
:root {
    --primary-color: #3498db;
    --secondary-color: #2ecc71;
    --accent-color: #e67e22;
    --text-color: #333;
    --bg-color: #f0f2f5;
    --card-bg: white;
    --border-color: #ddd;
    --shadow-color: rgba(0,0,0,0.1);
    --box-shadow-light: 0 2px 10px rgba(0,0,0,0.1);
    --gap-size: 20px;
}

/* _base.css */

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
    padding-bottom: 50px;
}

a {
    color: var(--primary-color);
    text-decoration: none;
    transition: color 0.2s ease;
}
a:hover {
    color: #2980b9;
}

ul {
    list-style: none;
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

/* _layout.css */

.l-header {
    background-color: var(--primary-color);
    color: white;
    text-align: center;
    padding: calc(var(--gap-size) * 1.5) var(--gap-size);
    box-shadow: 0 3px 6px var(--shadow-color);
    margin-bottom: var(--gap-size);
}
.l-header__title {
    font-size: 2.8em;
    margin-bottom: calc(var(--gap-size) / 2);
}

.l-main-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--gap-size);
}

.l-section {
    background-color: var(--card-bg);
    padding: calc(var(--gap-size) * 1.5);
    margin-bottom: var(--gap-size);
    border-radius: 8px;
    box-shadow: 0 2px 10px var(--shadow-color);
}
.l-section__title {
    color: var(--primary-color);
    font-size: 2em;
    margin-bottom: calc(var(--gap-size) * 1.5);
    text-align: center;
}

.post-grid {
    display: grid;
    /* 좁은 화면에서는 300px 대신 부모 폭까지 줄어듦 */
    grid-template-columns: repeat(auto-fit, minmax(min(300px, 100%), 1fr));
    gap: var(--gap-size);
}

.l-footer {
    background-color: var(--primary-color);
    color: white;
    text-align: center;
    padding: var(--gap-size);
    margin-top: 50px;
    font-size: 0.9em;
}

/* _module.css */

/* Button Module */
.button {
    display: inline-block;
    padding: 10px 15px;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-size: 0.9em;
    font-weight: bold;
    transition: background-color 0.2s ease, transform 0.2s ease;
}
.button--primary {
    background-color: var(--primary-color);
    color: white;
}
.button--secondary {
    background-color: var(--secondary-color);
    color: white;
}
.button:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0,0,0,0.15);
}
.button--primary:hover { background-color: #2980b9; }
.button--secondary:hover { background-color: #27ae60; }

/* Main Navigation Module */
.main-nav {
    background-color: #34495e;
    padding: 10px 0;
    text-align: center;
}
.main-nav__list {
    display: flex;
    flex-wrap: wrap; /* 좁은 화면에서는 메뉴가 줄을 바꿈 */
    justify-content: center;
    gap: 20px;
}
.main-nav__link {
    color: white;
    padding: 8px 15px;
    border-radius: 5px;
    transition: background-color 0.2s ease;
}
.main-nav__link:hover {
    background-color: rgba(255, 255, 255, 0.2);
}

/* Post Card Module */
.post-card {
    background-color: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    overflow: hidden; /* 둥근 모서리 밖으로 내용이 나가지 않도록 */
    box-shadow: var(--box-shadow-light);
    transition: transform 0.2s ease-out;
    display: flex;
    flex-direction: column;
}
.post-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 5px 15px rgba(0,0,0,0.15);
}
.post-card__content {
    padding: var(--gap-size);
    display: flex;
    flex-direction: column;
    flex-grow: 1; /* 콘텐츠 영역이 남은 공간 차지 */
}
.post-card__title {
    font-size: 1.3em;
    color: var(--primary-color);
    margin-bottom: calc(var(--gap-size) / 2);
}
.post-card__excerpt {
    font-size: 0.95em;
    color: var(--text-color);
    margin-bottom: var(--gap-size);
    flex-grow: 1; /* 발췌 부분이 남은 공간 차지 */
}
.post-card__read-more {
    align-self: flex-start; /* 버튼만 왼쪽 정렬 */
    margin-top: auto; /* 항상 하단에 붙도록 */
}

/* Post Card Modifier */
.post-card--featured {
    border-color: var(--accent-color);
    box-shadow: 0 5px 20px rgba(230, 126, 34, 0.3);
}

/* _state.css */

.is-active {
    background-color: rgba(255, 255, 255, 0.3); /* 활성 상태 */
    font-weight: bold;
}

.is-new::after {
    content: "NEW!";
    order: -1; /* Flex 컨테이너인 카드 안에서 맨 앞에 놓음 */
    align-self: flex-start; /* 카드 폭으로 늘어나지 않게 */
    margin: 10px 0 0 10px;
    background-color: #e74c3c;
    color: white;
    font-size: 0.7em;
    padding: 3px 8px;
    border-radius: 3px;
}