/* ========================
   CSS Variables & Reset
   ======================== */
:root {
  --bg-primary: #0a0a0a;
  --bg-secondary: #111111;
  --bg-card: #161616;
  --bg-card-hover: #1e1e1e;
  --accent-cyan: #00d4ff;
  --accent-purple: #7b2ff7;
  --accent-gradient: linear-gradient(135deg, #00d4ff, #7b2ff7);
  --text-primary: #f0f0f0;
  --text-secondary: #a0a0a0;
  --text-muted: #606060;
  --border: #2a2a2a;
  --border-accent: rgba(0, 212, 255, 0.3);
  --shadow-glow: 0 0 20px rgba(0, 212, 255, 0.15);
  --shadow-card: 0 4px 24px rgba(0, 0, 0, 0.4);
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 20px;
  --nav-height: 70px;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Courier New', monospace;
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  background-color: var(--bg-primary);
  color: var(--text-primary);
  font-family: 'Pretendard', 'Noto Sans KR', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  line-height: 1.6;
  overflow-x: hidden;
}

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

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

/* ========================
   Scrollbar
   ======================== */
::-webkit-scrollbar {
  width: 6px;
}
::-webkit-scrollbar-track {
  background: var(--bg-secondary);
}
::-webkit-scrollbar-thumb {
  background: var(--accent-purple);
  border-radius: 3px;
}
::-webkit-scrollbar-thumb:hover {
  background: var(--accent-cyan);
}

/* ========================
   Navbar
   ======================== */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--nav-height);
  background: rgba(10, 10, 10, 0.85);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border);
  z-index: 1000;
  display: flex;
  align-items: center;
  padding: 0 2rem;
  transition: border-color var(--transition);
}

.navbar.scrolled {
  border-bottom-color: var(--border-accent);
  box-shadow: 0 2px 20px rgba(0, 212, 255, 0.08);
}

.nav-inner {
  max-width: 1200px;
  width: 100%;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-logo {
  font-family: var(--font-mono);
  font-size: 1.3rem;
  font-weight: 700;
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  letter-spacing: -0.5px;
}

.nav-logo span {
  color: var(--accent-cyan);
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 0.25rem;
  list-style: none;
}

.nav-links a {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.5rem 0.9rem;
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-secondary);
  transition: color var(--transition), background var(--transition);
  position: relative;
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--text-primary);
  background: rgba(255, 255, 255, 0.05);
}

.nav-links a.active::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 16px;
  height: 2px;
  background: var(--accent-gradient);
  border-radius: 2px;
}

.nav-links .nav-icon {
  font-size: 1rem;
}

.nav-hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  padding: 8px;
  background: none;
  border: none;
}

.nav-hamburger span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--text-primary);
  border-radius: 2px;
  transition: var(--transition);
}

/* ========================
   Page Wrapper
   ======================== */
.page-wrapper {
  padding-top: var(--nav-height);
  min-height: 100vh;
}

/* ========================
   Section Commons
   ======================== */
.section {
  padding: 6rem 2rem;
  max-width: 1200px;
  margin: 0 auto;
}

.section-header {
  text-align: center;
  margin-bottom: 4rem;
}

.section-tag {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--accent-cyan);
  background: rgba(0, 212, 255, 0.08);
  border: 1px solid rgba(0, 212, 255, 0.2);
  padding: 0.3rem 0.9rem;
  border-radius: 999px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  margin-bottom: 1rem;
}

.section-title {
  font-size: clamp(1.8rem, 4vw, 2.6rem);
  font-weight: 800;
  letter-spacing: -1px;
  line-height: 1.2;
  margin-bottom: 1rem;
}

.section-title .highlight {
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.section-desc {
  font-size: 1.05rem;
  color: var(--text-secondary);
  max-width: 540px;
  margin: 0 auto;
}

/* ========================
   Cards
   ======================== */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  transition: border-color var(--transition), transform var(--transition), box-shadow var(--transition), background var(--transition);
}

.card:hover {
  border-color: var(--border-accent);
  background: var(--bg-card-hover);
  transform: translateY(-3px);
  box-shadow: var(--shadow-glow);
}

/* ========================
   Buttons
   ======================== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.75rem 1.5rem;
  border-radius: var(--radius-sm);
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  border: none;
}

.btn-primary {
  background: var(--accent-gradient);
  color: #fff;
  box-shadow: 0 4px 15px rgba(0, 212, 255, 0.25);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 25px rgba(0, 212, 255, 0.4);
}

.btn-outline {
  background: transparent;
  color: var(--text-primary);
  border: 1px solid var(--border);
}

.btn-outline:hover {
  border-color: var(--accent-cyan);
  color: var(--accent-cyan);
  background: rgba(0, 212, 255, 0.05);
}

/* ========================
   Tags / Badges
   ======================== */
.tag {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  padding: 0.3rem 0.7rem;
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 0.78rem;
  font-family: var(--font-mono);
  color: var(--text-secondary);
  white-space: nowrap;
  transition: var(--transition);
}

.tag:hover {
  border-color: var(--accent-cyan);
  color: var(--accent-cyan);
  background: rgba(0, 212, 255, 0.05);
}

/* ========================
   Page Header (for sub-pages)
   ======================== */
.page-hero {
  background: radial-gradient(ellipse at 50% 0%, rgba(123, 47, 247, 0.12) 0%, transparent 65%),
              radial-gradient(ellipse at 80% 50%, rgba(0, 212, 255, 0.06) 0%, transparent 60%);
  padding: 5rem 2rem 4rem;
  text-align: center;
  border-bottom: 1px solid var(--border);
  position: relative;
  overflow: hidden;
}

.page-hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background: url("data:image/svg+xml,%3Csvg width='60' height='60' viewBox='0 0 60 60' xmlns='http://www.w3.org/2000/svg'%3E%3Cg fill='none' fill-rule='evenodd'%3E%3Cg fill='%23ffffff' fill-opacity='0.015'%3E%3Cpath d='M36 34v-4h-2v4h-4v2h4v4h2v-4h4v-2h-4zm0-30V0h-2v4h-4v2h4v4h2V6h4V4h-4zM6 34v-4H4v4H0v2h4v4h2v-4h4v-2H6zM6 4V0H4v4H0v2h4v4h2V6h4V4H6z'/%3E%3C/g%3E%3C/g%3E%3C/svg%3E");
  pointer-events: none;
}

.page-hero-content {
  position: relative;
  z-index: 1;
  max-width: 700px;
  margin: 0 auto;
}

.page-hero .section-tag {
  margin-bottom: 1.2rem;
}

.page-hero h1 {
  font-size: clamp(2rem, 5vw, 3.2rem);
  font-weight: 800;
  letter-spacing: -1.5px;
  line-height: 1.15;
  margin-bottom: 1rem;
}

.page-hero p {
  font-size: 1.1rem;
  color: var(--text-secondary);
}

/* ========================
   Footer
   ======================== */
footer {
  border-top: 1px solid var(--border);
  padding: 2.5rem 2rem;
  text-align: center;
}

.footer-inner {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
}

.footer-links {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
  justify-content: center;
}

.footer-link {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  color: var(--text-secondary);
  font-size: 0.9rem;
  transition: color var(--transition);
  padding: 0.4rem 0.8rem;
  border-radius: var(--radius-sm);
}

.footer-link:hover {
  color: var(--accent-cyan);
  background: rgba(0, 212, 255, 0.05);
}

.footer-copy {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--text-muted);
}

/* ========================
   Skill Progress Bar
   ======================== */
.skill-bar {
  width: 100%;
  height: 4px;
  background: var(--border);
  border-radius: 2px;
  overflow: hidden;
  margin-top: 0.5rem;
}

.skill-bar-fill {
  height: 100%;
  background: var(--accent-gradient);
  border-radius: 2px;
  width: 0%;
  transition: width 1.2s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ========================
   Grid Layouts
   ======================== */
.grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: 1.5rem; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1.5rem; }
.grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 1.5rem; }

/* ========================
   Responsive
   ======================== */
@media (max-width: 1024px) {
  .grid-4 { grid-template-columns: repeat(2, 1fr); }
  .grid-3 { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 768px) {
  .section { padding: 4rem 1.25rem; }
  .grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr; }

  .nav-links {
    display: none;
    position: fixed;
    top: var(--nav-height);
    left: 0;
    right: 0;
    background: rgba(10, 10, 10, 0.98);
    backdrop-filter: blur(20px);
    flex-direction: column;
    padding: 1.5rem;
    gap: 0.5rem;
    border-bottom: 1px solid var(--border);
  }

  .nav-links.open {
    display: flex;
  }

  .nav-links a {
    padding: 0.75rem 1rem;
    font-size: 1rem;
  }

  .nav-hamburger {
    display: flex;
  }
}