/* ════════════════════════════════════════════
   Twin Willows — 메인 스타일시트
   CSS 변수 기반 테마, 반응형, 다크/라이트
   ════════════════════════════════════════════ */

/* ─── CSS 변수 ─── */
:root {
  /* 라이트 테마 (기본) */
  --color-bg: #FAFAFA;
  --color-surface: #FFFFFF;
  --color-text: #1A1A1A;
  --color-text-secondary: #6B7280;
  --color-accent: #2563EB;
  --color-accent-hover: #1D4ED8;
  --color-border: #E5E7EB;
  --color-success: #16A34A;
  --color-error: #DC2626;

  /* 타이포그래피 */
  --font-primary: 'Pretendard', system-ui, -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;
  --text-xs: 0.75rem;
  --text-sm: 0.875rem;
  --text-base: 1rem;
  --text-lg: 1.125rem;
  --text-xl: 1.25rem;
  --text-2xl: 1.5rem;
  --text-3xl: 1.875rem;
  --text-4xl: 2.25rem;
  --text-5xl: 3rem;

  /* 간격 */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --space-24: 6rem;

  /* 레이아웃 */
  --max-width: 1200px;
  --nav-height: 64px;
  --border-radius: 8px;
  --border-radius-lg: 12px;
  --border-radius-full: 9999px;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
  --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.07), 0 2px 4px -2px rgba(0,0,0,0.05);
  --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.08), 0 4px 6px -4px rgba(0,0,0,0.05);
  --transition: 0.2s ease;
  --transition-slow: 0.4s ease;
}

/* ─── 다크 테마 ─── */
[data-theme="dark"] {
  --color-bg: #0F0F0F;
  --color-surface: #1A1A1A;
  --color-text: #F5F5F5;
  --color-text-secondary: #9CA3AF;
  --color-accent: #3B82F6;
  --color-accent-hover: #60A5FA;
  --color-border: #2D2D2D;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.3);
  --shadow-md: 0 4px 6px rgba(0,0,0,0.3);
  --shadow-lg: 0 10px 15px rgba(0,0,0,0.4);
}

/* ─── 언어별 폰트 ─── */
html[lang="ko"] { --font-primary: 'Pretendard', system-ui, sans-serif; }
html[lang="en"] { --font-primary: 'Pretendard', 'Inter', system-ui, sans-serif; }
html[lang="ja"] { --font-primary: 'Noto Sans JP', 'Pretendard', system-ui, sans-serif; }

/* ─── 리셋 & 기본 ─── */
*, *::before, *::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: var(--nav-height);
}

body {
  font-family: var(--font-primary);
  font-size: var(--text-base);
  line-height: 1.7;
  color: var(--color-text);
  background-color: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  transition: background-color var(--transition), color var(--transition);
  word-break: keep-all;
  overflow-wrap: break-word;
}

body.nav-open {
  overflow: hidden;
}

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color var(--transition);
}
a:hover { color: var(--color-accent-hover); }

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

/* ─── 로딩 상태 ─── */
.loading .section { opacity: 0; }
.section {
  opacity: 1;
  transition: opacity 0.3s ease;
}

/* ─── 컨테이너 ─── */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-6);
}

/* ─── 섹션 공통 ─── */
.section {
  padding: var(--space-20) 0;
}

.section-header {
  text-align: center;
  margin-bottom: var(--space-12);
}

.section-title {
  font-size: var(--text-3xl);
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: var(--space-3);
}

.section-subtitle {
  font-size: var(--text-lg);
  color: var(--color-text-secondary);
}

/* ═══════════════════════
   네비게이션
   ═══════════════════════ */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--nav-height);
  z-index: 1000;
  background: transparent;
  transition: background-color var(--transition), box-shadow var(--transition), backdrop-filter var(--transition);
}

.nav--scrolled {
  background: rgba(255,255,255,0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  box-shadow: var(--shadow-sm);
}
[data-theme="dark"] .nav--scrolled {
  background: rgba(15,15,15,0.85);
}

.nav__container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-6);
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-6);
}

.nav__logo {
  font-size: var(--text-xl);
  font-weight: 700;
  color: var(--color-text);
  text-decoration: none;
  flex-shrink: 0;
}
.nav__logo:hover { color: var(--color-accent); }

.nav__menu {
  list-style: none;
  display: flex;
  align-items: center;
  gap: var(--space-1);
}

.nav__link {
  display: inline-block;
  padding: var(--space-2) var(--space-3);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-text-secondary);
  text-decoration: none;
  border-radius: var(--border-radius);
  transition: color var(--transition), background-color var(--transition);
}
.nav__link:hover {
  color: var(--color-text);
  background: rgba(0,0,0,0.04);
}
[data-theme="dark"] .nav__link:hover {
  background: rgba(255,255,255,0.06);
}
.nav__link--active {
  color: var(--color-accent);
}

.nav__controls {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

/* 테마 토글 */
.nav__theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border: none;
  background: none;
  color: var(--color-text-secondary);
  cursor: pointer;
  border-radius: var(--border-radius);
  transition: color var(--transition), background-color var(--transition);
}
.nav__theme-toggle:hover {
  color: var(--color-text);
  background: rgba(0,0,0,0.04);
}
[data-theme="dark"] .nav__theme-toggle:hover {
  background: rgba(255,255,255,0.06);
}

.theme-icon--dark { display: none; }
[data-theme="dark"] .theme-icon--light { display: none; }
[data-theme="dark"] .theme-icon--dark { display: block; }

/* 햄버거 */
.nav__hamburger {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 36px;
  height: 36px;
  border: none;
  background: none;
  cursor: pointer;
  padding: 6px;
}
.nav__hamburger span {
  display: block;
  width: 100%;
  height: 2px;
  background: var(--color-text);
  border-radius: 2px;
  transition: transform var(--transition), opacity var(--transition);
}
.nav__hamburger--open span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}
.nav__hamburger--open span:nth-child(2) {
  opacity: 0;
}
.nav__hamburger--open span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* 언어 전환기 */
.lang-selector {
  position: relative;
}

.lang-selector__toggle {
  display: flex;
  align-items: center;
  gap: var(--space-1);
  padding: var(--space-1) var(--space-2);
  border: 1px solid var(--color-border);
  background: transparent;
  color: var(--color-text-secondary);
  font-size: var(--text-sm);
  border-radius: var(--border-radius);
  cursor: pointer;
  transition: all var(--transition);
}
.lang-selector__toggle:hover {
  color: var(--color-text);
  border-color: var(--color-text-secondary);
}

.lang-selector__icon { flex-shrink: 0; }
.lang-selector__chevron {
  transition: transform var(--transition);
}
.lang-selector--open .lang-selector__chevron {
  transform: rotate(180deg);
}

.lang-selector__menu {
  display: none;
  position: absolute;
  top: calc(100% + 4px);
  right: 0;
  min-width: 140px;
  list-style: none;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius);
  box-shadow: var(--shadow-md);
  overflow: hidden;
  z-index: 100;
}
.lang-selector--open .lang-selector__menu {
  display: block;
}

.lang-selector__item a {
  display: block;
  padding: var(--space-2) var(--space-4);
  font-size: var(--text-sm);
  color: var(--color-text);
  text-decoration: none;
  transition: background-color var(--transition);
}
.lang-selector__item a:hover {
  background: rgba(0,0,0,0.04);
}
[data-theme="dark"] .lang-selector__item a:hover {
  background: rgba(255,255,255,0.06);
}
.lang-selector__item--active a {
  color: var(--color-accent);
  font-weight: 600;
}

/* ═══════════════════════
   히어로
   ═══════════════════════ */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding-top: var(--nav-height);
}

.hero__container {
  text-align: center;
  max-width: 800px;
  margin: 0 auto;
  padding: var(--space-8) var(--space-6);
}

.hero__headline {
  font-size: var(--text-4xl);
  font-weight: 800;
  line-height: 1.35;
  margin-bottom: var(--space-6);
  color: var(--color-text);
}

.hero__subheadline {
  font-size: var(--text-xl);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-10);
  line-height: 1.5;
}

.hero__cta {
  display: inline-block;
}

/* ═══════════════════════
   버튼
   ═══════════════════════ */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  font-family: var(--font-primary);
  font-weight: 600;
  border: none;
  border-radius: var(--border-radius);
  cursor: pointer;
  text-decoration: none;
  transition: all var(--transition);
}

.btn--primary {
  background: var(--color-accent);
  color: #FFFFFF;
  padding: var(--space-3) var(--space-6);
  font-size: var(--text-base);
}
.btn--primary:hover {
  background: var(--color-accent-hover);
  color: #FFFFFF;
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

.btn--lg {
  padding: var(--space-4) var(--space-8);
  font-size: var(--text-lg);
}

/* ═══════════════════════
   카드
   ═══════════════════════ */
.card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-lg);
  padding: var(--space-8);
  transition: transform var(--transition), box-shadow var(--transition);
}
.card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

/* ─── 태그 ─── */
.tag {
  display: inline-block;
  padding: var(--space-1) var(--space-3);
  font-size: var(--text-xs);
  font-weight: 500;
  border-radius: var(--border-radius-full);
  background: rgba(37, 99, 235, 0.08);
  color: var(--color-accent);
}
.tag--outline {
  background: transparent;
  border: 1px solid var(--color-border);
  color: var(--color-text-secondary);
}

/* ═══════════════════════
   서비스
   ═══════════════════════ */
.services__grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-6);
}

.services__icon {
  font-size: 2.5rem;
  margin-bottom: var(--space-4);
}

.services__title {
  font-size: var(--text-xl);
  font-weight: 700;
  margin-bottom: var(--space-3);
}

.services__desc {
  font-size: var(--text-base);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-4);
  line-height: 1.75;
}

.services__tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

/* ═══════════════════════
   사례 연구
   ═══════════════════════ */
.cases__grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-6);
}

.cases__header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--space-3);
}

.cases__industry {
  font-size: var(--text-sm);
  color: var(--color-accent);
  font-weight: 600;
}

.cases__period {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
}

.cases__client {
  font-size: var(--text-xl);
  font-weight: 700;
  margin-bottom: var(--space-4);
}

.cases__label {
  display: block;
  font-size: var(--text-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text);
  margin-bottom: var(--space-1);
}

.cases__problem,
.cases__solution {
  font-size: var(--text-base);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-4);
  line-height: 1.75;
}

.cases__tech {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin-bottom: var(--space-4);
}

.cases__results {
  list-style: none;
  margin-top: var(--space-4);
  padding-top: var(--space-4);
  border-top: 1px solid var(--color-border);
}

.cases__result-item {
  position: relative;
  padding-left: var(--space-6);
  margin-bottom: var(--space-2);
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
}
.cases__result-item::before {
  content: '';
  position: absolute;
  left: 0;
  top: 0.5em;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--color-success);
}

/* ═══════════════════════
   Why Us (강점)
   ═══════════════════════ */
#why-us {
  background: var(--color-surface);
}

.strengths__grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-6);
  text-align: center;
}

.strengths__item {
  padding: var(--space-6);
}

.strengths__metric {
  font-size: var(--text-4xl);
  font-weight: 800;
  color: var(--color-accent);
  margin-bottom: var(--space-2);
}

.strengths__label {
  font-size: var(--text-base);
  font-weight: 600;
  margin-bottom: var(--space-2);
}

.strengths__desc {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
  line-height: 1.7;
}

/* ═══════════════════════
   프로세스
   ═══════════════════════ */
.process__timeline {
  max-width: 700px;
  margin: 0 auto;
  position: relative;
}

.process__timeline::before {
  content: '';
  position: absolute;
  left: 28px;
  top: 0;
  bottom: 0;
  width: 2px;
  background: var(--color-border);
}

.process__step {
  display: flex;
  gap: var(--space-6);
  margin-bottom: var(--space-8);
  position: relative;
}
.process__step:last-child { margin-bottom: 0; }

.process__number {
  flex-shrink: 0;
  width: 56px;
  height: 56px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--color-accent);
  color: #FFFFFF;
  font-size: var(--text-lg);
  font-weight: 700;
  border-radius: 50%;
  z-index: 1;
}

.process__content {
  flex: 1;
  min-width: 0;
  padding-top: var(--space-4);
}

.process__title {
  font-size: var(--text-lg);
  font-weight: 700;
  margin-bottom: var(--space-2);
}

.process__desc {
  font-size: var(--text-base);
  color: var(--color-text-secondary);
  line-height: 1.75;
}

/* ═══════════════════════
   기술 스택
   ═══════════════════════ */
#tech {
  background: var(--color-surface);
}

.tech__grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-8);
}

.tech__category-name {
  font-size: var(--text-base);
  font-weight: 700;
  color: var(--color-accent);
  margin-bottom: var(--space-4);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.tech__items {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.tech__item {
  padding: var(--space-3) var(--space-4);
  background: var(--color-bg);
  border-radius: var(--border-radius);
  border: 1px solid var(--color-border);
  transition: all var(--transition);
}
.tech__item:hover {
  border-color: var(--color-accent);
  transform: translateX(4px);
}

.tech__item-name {
  font-size: var(--text-sm);
  font-weight: 500;
}

/* ═══════════════════════
   문의 폼
   ═══════════════════════ */
.contact__form {
  max-width: 640px;
  margin: 0 auto;
}

.form-group {
  margin-bottom: var(--space-6);
}

.form-label {
  display: block;
  font-size: var(--text-sm);
  font-weight: 600;
  margin-bottom: var(--space-2);
  color: var(--color-text);
}

.form-required {
  color: var(--color-error);
}

.form-input {
  width: 100%;
  padding: var(--space-3) var(--space-4);
  font-family: var(--font-primary);
  font-size: var(--text-base);
  color: var(--color-text);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius);
  transition: border-color var(--transition), box-shadow var(--transition);
  appearance: none;
}
.form-input:focus {
  outline: none;
  border-color: var(--color-accent);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}
[data-theme="dark"] .form-input:focus {
  box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.15);
}

.form-textarea {
  resize: vertical;
  min-height: 120px;
}

.form-select {
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%236B7280' stroke-width='2'%3E%3Cpath d='M6 9l6 6 6-6'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 12px center;
  padding-right: var(--space-10);
}

.contact__submit {
  width: 100%;
  margin-top: var(--space-4);
}

.contact__message {
  text-align: center;
  margin-top: var(--space-4);
  padding: var(--space-3) var(--space-4);
  border-radius: var(--border-radius);
  font-size: var(--text-sm);
  font-weight: 500;
  min-height: 1.5rem;
}
.contact__message--success {
  background: rgba(22, 163, 74, 0.08);
  color: var(--color-success);
}
.contact__message--error {
  background: rgba(220, 38, 38, 0.08);
  color: var(--color-error);
}

/* ═══════════════════════
   트러블슈팅
   ═══════════════════════ */
.ts__grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-6);
}

.ts__date {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
}

.ts__title {
  font-size: var(--text-lg);
  font-weight: 700;
  margin: var(--space-2) 0 var(--space-3);
}

.ts__env {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
  font-family: var(--font-mono);
  margin-bottom: var(--space-4);
}

.ts__tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

/* ═══════════════════════
   푸터
   ═══════════════════════ */
#footer {
  background: var(--color-surface);
  border-top: 1px solid var(--color-border);
  padding: var(--space-12) 0;
}

.footer__container {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-6);
  text-align: center;
}

.footer__company {
  font-size: var(--text-lg);
  font-weight: 700;
}

.footer__detail {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
}

.footer__social {
  display: flex;
  gap: var(--space-6);
}

.footer__social-link {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
  text-decoration: none;
  transition: color var(--transition);
}
.footer__social-link:hover {
  color: var(--color-accent);
}

.footer__copyright {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
}

/* ═══════════════════════
   맨 위로 버튼
   ═══════════════════════ */
.back-to-top {
  position: fixed;
  bottom: var(--space-8);
  right: var(--space-8);
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 50%;
  color: var(--color-text);
  cursor: pointer;
  box-shadow: var(--shadow-md);
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: all var(--transition);
  z-index: 50;
}
.back-to-top--visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}
.back-to-top:hover {
  background: var(--color-accent);
  color: #FFFFFF;
  border-color: var(--color-accent);
}

/* ═══════════════════════
   스크롤 애니메이션
   ═══════════════════════ */
[data-animate="fade-up"] {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}
[data-animate="fade-up"].animated {
  opacity: 1;
  transform: translateY(0);
}

/* ═══════════════════════
   반응형
   ═══════════════════════ */

/* 태블릿 이하 */
@media (max-width: 1023px) {
  .services__grid,
  .cases__grid,
  .ts__grid {
    grid-template-columns: 1fr;
  }

  .strengths__grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .tech__grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

/* 모바일 */
@media (max-width: 767px) {
  :root {
    --text-4xl: 1.875rem;
    --text-5xl: 2.25rem;
  }

  .section {
    padding: var(--space-16) 0;
  }

  .section-title {
    font-size: var(--text-2xl);
  }

  /* 네비게이션 모바일 */
  .nav__menu {
    display: none;
    position: fixed;
    top: var(--nav-height);
    left: 0;
    right: 0;
    bottom: 0;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: var(--space-4);
    background: var(--color-bg);
    z-index: 999;
  }
  .nav__menu--open {
    display: flex;
  }

  .nav__link {
    font-size: var(--text-xl);
    padding: var(--space-3) var(--space-6);
  }

  .nav__hamburger {
    display: flex;
  }

  /* 강점 */
  .strengths__grid {
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-4);
  }

  .strengths__metric {
    font-size: var(--text-3xl);
  }

  /* 기술 스택 */
  .tech__grid {
    grid-template-columns: 1fr 1fr;
    gap: var(--space-6);
  }

  /* 프로세스 */
  .process__timeline::before {
    left: 20px;
  }

  .process__number {
    width: 40px;
    height: 40px;
    font-size: var(--text-base);
  }

  /* 히어로 */
  .hero__headline {
    font-size: var(--text-3xl);
  }

  .hero__subheadline {
    font-size: var(--text-lg);
  }

  /* 푸터 */
  .footer__container {
    gap: var(--space-4);
  }

  /* 맨 위로 */
  .back-to-top {
    bottom: var(--space-4);
    right: var(--space-4);
  }
}

@media (max-width: 480px) {
  .hero__headline {
    font-size: 1.5rem;
  }

  .hero__subheadline {
    font-size: var(--text-base);
  }

  .card {
    padding: var(--space-6);
  }

  .strengths__grid {
    grid-template-columns: 1fr 1fr;
  }

  .tech__grid {
    grid-template-columns: 1fr;
  }

  .container {
    padding: 0 var(--space-4);
  }
}

/* ─── 데스크톱 큰 화면 ─── */
@media (min-width: 1280px) {
  .hero__headline {
    font-size: var(--text-5xl);
  }
}