/* ===== CSS 변수 ===== */
:root {
  --color-primary: #4f46e5;
  --color-primary-dark: #3730a3;
  --color-text: #1a1a2e;
  --color-text-muted: #6b7280;
  --color-bg: #ffffff;
  --color-bg-gray: #f8f9fa;
  --color-border: #e5e7eb;
  --font-body: 'Inter', sans-serif;
  --font-heading: 'Poppins', sans-serif;
  --radius: 12px;
  --shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
  --transition: 0.25s ease;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-body);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

a {
  text-decoration: none;
  color: inherit;
}

/* ===== 공통 ===== */
.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 0 24px;
}

.section {
  padding: 96px 0;
}

.section--gray {
  background: var(--color-bg-gray);
}

.section__title {
  font-family: var(--font-heading);
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 48px;
  position: relative;
  display: inline-block;
}

.section__title::after {
  content: '';
  position: absolute;
  left: 0;
  bottom: -8px;
  width: 48px;
  height: 4px;
  background: var(--color-primary);
  border-radius: 2px;
}

.btn {
  display: inline-block;
  background: var(--color-primary);
  color: #fff;
  padding: 14px 36px;
  border-radius: 50px;
  font-weight: 600;
  font-size: 1rem;
  transition: background var(--transition), transform var(--transition);
}

.btn:hover {
  background: var(--color-primary-dark);
  transform: translateY(-2px);
}

/* ===== 네비게이션 ===== */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  padding: 18px 0;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-bottom: 1px solid transparent;
  transition: border-color var(--transition), box-shadow var(--transition);
}

.nav.scrolled {
  border-color: var(--color-border);
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.06);
}

.nav__inner {
  max-width: 900px;
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav__logo {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 1.2rem;
  color: var(--color-primary);
}

.nav__links {
  list-style: none;
  display: flex;
  gap: 36px;
}

.nav__links a {
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--color-text-muted);
  transition: color var(--transition);
}

.nav__links a:hover,
.nav__links a.active {
  color: var(--color-primary);
}

/* ===== Hero ===== */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  padding: 120px 0 80px;
  background: linear-gradient(135deg, #f5f3ff 0%, #ede9fe 50%, #fff 100%);
}

.hero__greeting {
  font-size: 1.1rem;
  color: var(--color-primary);
  font-weight: 500;
  margin-bottom: 12px;
  opacity: 0;
  animation: fadeUp 0.6s ease forwards 0.1s;
}

.hero__name {
  font-family: var(--font-heading);
  font-size: clamp(2.5rem, 6vw, 4.5rem);
  font-weight: 800;
  line-height: 1.15;
  color: var(--color-text);
  margin-bottom: 20px;
  opacity: 0;
  animation: fadeUp 0.6s ease forwards 0.25s;
}

.hero__tagline {
  font-size: 1.15rem;
  color: var(--color-text-muted);
  max-width: 520px;
  margin-bottom: 40px;
  opacity: 0;
  animation: fadeUp 0.6s ease forwards 0.4s;
}

.hero .btn {
  opacity: 0;
  animation: fadeUp 0.6s ease forwards 0.55s;
}

/* ===== About ===== */
.about__text {
  font-size: 1.1rem;
  color: var(--color-text-muted);
  max-width: 640px;
  line-height: 1.9;
}

/* ===== Skills ===== */
.skills__grid {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.skill-tag {
  background: #fff;
  border: 2px solid var(--color-border);
  color: var(--color-text);
  padding: 8px 22px;
  border-radius: 50px;
  font-size: 0.95rem;
  font-weight: 500;
  transition: border-color var(--transition), color var(--transition), background var(--transition);
}

.skill-tag:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
  background: #f5f3ff;
}

/* ===== Projects ===== */
.projects__grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 24px;
}

.project-card {
  background: #fff;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 28px 24px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  box-shadow: var(--shadow);
  transition: transform var(--transition), box-shadow var(--transition);
}

.project-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 12px 32px rgba(79, 70, 229, 0.12);
}

.project-card__header {
  display: flex;
  align-items: center;
  gap: 10px;
}

.project-card__icon {
  font-size: 1.5rem;
}

.project-card__title {
  font-family: var(--font-heading);
  font-size: 1.1rem;
  font-weight: 700;
}

.project-card__desc {
  font-size: 0.9rem;
  color: var(--color-text-muted);
  line-height: 1.7;
  flex: 1;
}

.project-card__tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.project-card__tags span {
  background: #f5f3ff;
  color: var(--color-primary);
  font-size: 0.78rem;
  font-weight: 600;
  padding: 3px 10px;
  border-radius: 4px;
}

.project-card__link {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--color-primary);
  transition: gap var(--transition);
  margin-top: 4px;
}

.project-card__link:hover {
  text-decoration: underline;
}

/* ===== Contact ===== */
.contact__sub {
  color: var(--color-text-muted);
  margin-bottom: 36px;
  font-size: 1.05rem;
}

.contact__links {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
}

.contact__item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 14px 28px;
  border: 2px solid var(--color-border);
  border-radius: 50px;
  font-weight: 500;
  font-size: 0.95rem;
  transition: border-color var(--transition), color var(--transition), background var(--transition);
}

.contact__item svg {
  width: 20px;
  height: 20px;
  flex-shrink: 0;
}

.contact__item:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
  background: #f5f3ff;
}

/* ===== Footer ===== */
.footer {
  text-align: center;
  padding: 32px 24px;
  font-size: 0.875rem;
  color: var(--color-text-muted);
  border-top: 1px solid var(--color-border);
}

/* ===== 애니메이션 ===== */
@keyframes fadeUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.fade-in {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.55s ease, transform 0.55s ease;
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ===== 반응형 ===== */
@media (max-width: 640px) {
  .nav__links {
    gap: 20px;
  }

  .section {
    padding: 72px 0;
  }

  .section__title {
    font-size: 1.6rem;
  }

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

  .contact__links {
    flex-direction: column;
  }

  .contact__item {
    justify-content: center;
  }
}