/* ========================================
   DESIGN SYSTEM — Corporate Engineering Profile
   ======================================== */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&display=swap');

:root {
  --bg: #FFFFFF;
  --bg-alt: #F8FAFC;
  --bg-elevated: #FFFFFF;
  --text-primary: #0F172A;
  --text-secondary: #475569;
  --text-tertiary: #94A3B8;
  --border: #E2E8F0;
  --border-light: #F1F5F9;
  --accent: #2563EB;
  --accent-light: #DBEAFE;
  --accent-dark: #1D4ED8;
  --accent-subtle: #EFF6FF;
  --success: #059669;
  --nav-height: 64px;
  --max-w: 1120px;
  --transition: 0.2s cubic-bezier(0.4,0,0.2,1);
}

[data-theme="dark"] {
  --bg: #0F172A;
  --bg-alt: #1E293B;
  --bg-elevated: #1E293B;
  --text-primary: #F1F5F9;
  --text-secondary: #94A3B8;
  --text-tertiary: #64748B;
  --border: #334155;
  --border-light: #1E293B;
  --accent: #3B82F6;
  --accent-light: #1E3A5F;
  --accent-dark: #60A5FA;
  --accent-subtle: #172554;
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--nav-height) + 24px);
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background: var(--bg);
  color: var(--text-primary);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

/* ---- UTILITY ---- */
.container { max-width: var(--max-w); margin: 0 auto; padding: 0 24px; }
@media (min-width: 768px) { .container { padding: 0 40px; } }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); border: 0; }

/* ---- NAVIGATION ---- */
.nav {
  position: sticky; top: 0; z-index: 100;
  background: rgba(255,255,255,0.92);
  backdrop-filter: blur(12px); -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  height: var(--nav-height);
  transition: box-shadow var(--transition);
}
[data-theme="dark"] .nav { background: rgba(15,23,42,0.92); }
.nav.scrolled { box-shadow: 0 1px 3px rgba(0,0,0,0.06); }
.nav-inner {
  max-width: var(--max-w); margin: 0 auto; padding: 0 24px;
  display: flex; align-items: center; justify-content: space-between;
  height: 100%;
}
@media (min-width: 768px) { .nav-inner { padding: 0 40px; } }
.nav-brand { font-weight: 700; font-size: 1rem; color: var(--text-primary); text-decoration: none; letter-spacing: -0.02em; }
.nav-links { display: none; gap: 32px; align-items: center; list-style: none; }
@media (min-width: 900px) { .nav-links { display: flex; } }
.nav-links a {
  font-size: 0.8125rem; font-weight: 500; color: var(--text-secondary);
  text-decoration: none; transition: color var(--transition); letter-spacing: 0.01em;
  position: relative; padding: 4px 0;
}
.nav-links a::after {
  content: ''; position: absolute; bottom: -2px; left: 0; width: 0; height: 2px;
  background: var(--accent); transition: width var(--transition); border-radius: 1px;
}
.nav-links a:hover, .nav-links a.active { color: var(--accent); }
.nav-links a:hover::after, .nav-links a.active::after { width: 100%; }
.nav-links a:focus-visible { outline: 2px solid var(--accent); outline-offset: 4px; border-radius: 2px; }
.nav-actions { display: flex; align-items: center; gap: 12px; }
.nav-ext { font-size: 0.8125rem; font-weight: 500; color: var(--text-tertiary); text-decoration: none; transition: color var(--transition); display: none; }
@media (min-width: 900px) { .nav-ext { display: inline; } }
.nav-ext:hover { color: var(--accent); }

/* Theme Toggle */
.theme-toggle {
  background: none; border: 1px solid var(--border); border-radius: 8px;
  width: 36px; height: 36px; cursor: pointer; display: flex; align-items: center;
  justify-content: center; color: var(--text-secondary); transition: all var(--transition);
}
.theme-toggle:hover { border-color: var(--accent); color: var(--accent); }
.theme-toggle svg { width: 18px; height: 18px; }

/* Mobile Menu */
.mobile-toggle {
  display: flex; flex-direction: column; gap: 5px; background: none; border: none;
  cursor: pointer; padding: 4px; width: 28px;
}
@media (min-width: 900px) { .mobile-toggle { display: none; } }
.mobile-toggle span {
  display: block; height: 2px; background: var(--text-primary);
  border-radius: 1px; transition: all var(--transition);
}
.mobile-toggle.open span:nth-child(1) { transform: rotate(45deg) translate(5px, 5px); }
.mobile-toggle.open span:nth-child(2) { opacity: 0; }
.mobile-toggle.open span:nth-child(3) { transform: rotate(-45deg) translate(5px, -5px); }

.mobile-menu {
  display: none; position: fixed; top: var(--nav-height); left: 0; right: 0;
  background: var(--bg); border-bottom: 1px solid var(--border);
  padding: 24px; z-index: 99;
}
.mobile-menu.open { display: block; }
.mobile-menu a {
  display: block; padding: 12px 0; font-size: 0.9375rem; font-weight: 500;
  color: var(--text-secondary); text-decoration: none; border-bottom: 1px solid var(--border-light);
}
.mobile-menu a:last-child { border-bottom: none; }
.mobile-menu a:hover { color: var(--accent); }

/* ---- SECTION SHARED ---- */
section { padding: 80px 0; }
@media (min-width: 768px) { section { padding: 100px 0; } }
.section-label {
  font-size: 0.75rem; font-weight: 600; letter-spacing: 0.08em;
  text-transform: uppercase; color: var(--accent); margin-bottom: 12px;
}
.section-title {
  font-size: 1.75rem; font-weight: 700; letter-spacing: -0.025em;
  color: var(--text-primary); margin-bottom: 16px; line-height: 1.2;
}
@media (min-width: 768px) { .section-title { font-size: 2rem; } }
.section-subtitle { font-size: 1rem; color: var(--text-secondary); max-width: 640px; line-height: 1.7; }

/* ---- HERO ---- */
.hero { padding: 80px 0 60px; }
@media (min-width: 768px) { .hero { padding: 100px 0 80px; } }
.hero-grid { display: grid; gap: 48px; align-items: center; }
@media (min-width: 768px) { .hero-grid { grid-template-columns: 1fr auto; gap: 64px; } }
.hero-meta {
  display: flex; align-items: center; gap: 8px; margin-bottom: 16px;
  font-size: 0.8125rem; color: var(--text-secondary);
}
.hero-status {
  width: 8px; height: 8px; background: var(--success); border-radius: 50%;
  display: inline-block; animation: pulse-dot 2s ease-in-out infinite;
}
@keyframes pulse-dot { 0%, 100% { opacity: 1; } 50% { opacity: 0.4; } }
.hero h1 {
  font-size: 2.25rem; font-weight: 800; letter-spacing: -0.03em;
  line-height: 1.15; margin-bottom: 8px;
}
@media (min-width: 768px) { .hero h1 { font-size: 3rem; } }
.hero-role {
  font-size: 1.0625rem; font-weight: 500; color: var(--accent);
  margin-bottom: 6px;
}
.hero-spec { font-size: 0.875rem; color: var(--text-tertiary); margin-bottom: 20px; }
.hero-desc { font-size: 0.9375rem; color: var(--text-secondary); max-width: 540px; line-height: 1.7; margin-bottom: 32px; }
.hero-cta { display: flex; flex-wrap: wrap; gap: 12px; margin-bottom: 32px; }
.hero-links { display: flex; gap: 16px; }
.hero-links a {
  font-size: 0.8125rem; font-weight: 500; color: var(--text-tertiary);
  text-decoration: none; transition: color var(--transition);
  display: flex; align-items: center; gap: 6px;
}
.hero-links a:hover { color: var(--accent); }
.hero-photo {
  width: 200px; height: 200px; border-radius: 16px; object-fit: cover;
  border: 2px solid var(--border); filter: grayscale(10%);
}
@media (max-width: 767px) { .hero-photo { width: 120px; height: 120px; border-radius: 12px; } }
.hero-focus {
  display: grid; grid-template-columns: repeat(2, 1fr); gap: 8px;
  margin-top: 40px; padding-top: 40px; border-top: 1px solid var(--border);
}
@media (min-width: 640px) { .hero-focus { grid-template-columns: repeat(4, 1fr); } }
.focus-item {
  padding: 12px 16px; background: var(--bg-alt); border-radius: 8px;
  font-size: 0.8125rem; font-weight: 500; color: var(--text-secondary);
  border: 1px solid var(--border-light); text-align: center;
}

/* ---- BUTTONS ---- */
.btn {
  display: inline-flex; align-items: center; gap: 8px;
  font-family: inherit; font-size: 0.875rem; font-weight: 600;
  padding: 10px 24px; border-radius: 8px; border: none;
  cursor: pointer; text-decoration: none; transition: all var(--transition);
  line-height: 1.5;
}
.btn:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.btn-primary { background: var(--accent); color: #fff; }
.btn-primary:hover { background: var(--accent-dark); transform: translateY(-1px); box-shadow: 0 4px 12px rgba(37,99,235,0.25); }
.btn-secondary { background: transparent; color: var(--text-primary); border: 1px solid var(--border); }
.btn-secondary:hover { border-color: var(--accent); color: var(--accent); }
.btn-ghost { background: transparent; color: var(--accent); padding: 10px 0; }
.btn-ghost:hover { opacity: 0.8; }
.btn-sm { font-size: 0.8125rem; padding: 8px 16px; }

/* ---- CARDS ---- */
.card {
  background: var(--bg-elevated); border: 1px solid var(--border);
  border-radius: 12px; padding: 28px; transition: all var(--transition);
}
.card:hover { border-color: var(--accent); box-shadow: 0 4px 16px rgba(0,0,0,0.04); }

/* ---- EXPERIENCE TIMELINE ---- */
.timeline { position: relative; }
.timeline-item { display: grid; gap: 16px; padding: 28px 0; border-bottom: 1px solid var(--border-light); }
@media (min-width: 768px) { .timeline-item { grid-template-columns: 200px 1fr; gap: 40px; } }
.timeline-item:last-child { border-bottom: none; }
.timeline-date { font-size: 0.8125rem; font-weight: 500; color: var(--text-tertiary); padding-top: 4px; }
.timeline-content h3 { font-size: 1.0625rem; font-weight: 700; margin-bottom: 4px; }
.timeline-company { font-size: 0.875rem; font-weight: 600; color: var(--accent); margin-bottom: 12px; }
.timeline-desc { font-size: 0.875rem; color: var(--text-secondary); line-height: 1.7; margin-bottom: 16px; }
.tech-tags { display: flex; flex-wrap: wrap; gap: 6px; }
.tech-tag {
  font-size: 0.75rem; font-weight: 500; padding: 4px 10px;
  background: var(--accent-subtle); color: var(--accent);
  border-radius: 4px; border: 1px solid transparent;
}

/* ---- PROJECT CARDS ---- */
.project-grid { display: grid; gap: 20px; }
@media (min-width: 768px) { .project-grid { grid-template-columns: repeat(2, 1fr); } }
.project-card {
  background: var(--bg-elevated); border: 1px solid var(--border);
  border-radius: 12px; padding: 28px; transition: all var(--transition);
  position: relative;
}
.project-card:hover { border-color: var(--accent); box-shadow: 0 8px 24px rgba(0,0,0,0.05); }
.project-category {
  font-size: 0.6875rem; font-weight: 600; text-transform: uppercase;
  letter-spacing: 0.06em; color: var(--accent); margin-bottom: 12px;
}
.project-card h3 { font-size: 1.125rem; font-weight: 700; margin-bottom: 12px; line-height: 1.35; }
.project-card p { font-size: 0.875rem; color: var(--text-secondary); line-height: 1.7; margin-bottom: 16px; }
.project-details {
  display: none; padding-top: 16px; margin-top: 16px;
  border-top: 1px solid var(--border-light);
  font-size: 0.8125rem; color: var(--text-secondary); line-height: 1.7;
}
.project-details.open { display: block; }
.project-details h4 { font-size: 0.8125rem; font-weight: 700; color: var(--text-primary); margin: 16px 0 8px; }
.project-details h4:first-child { margin-top: 0; }
.project-details ul { padding-left: 20px; margin-bottom: 12px; }
.project-details li { margin-bottom: 4px; }
.project-toggle {
  font-size: 0.8125rem; font-weight: 600; color: var(--accent);
  background: none; border: none; cursor: pointer; padding: 0;
  transition: opacity var(--transition);
}
.project-toggle:hover { opacity: 0.7; }

/* Featured Project */
.featured-project {
  background: var(--bg-elevated); border: 1px solid var(--border);
  border-radius: 16px; padding: 40px; margin-bottom: 32px;
}
@media (max-width: 767px) { .featured-project { padding: 24px; } }
.featured-project .project-category { color: var(--success); }

/* ---- CAPABILITY GRID ---- */
.cap-grid { display: grid; gap: 20px; }
@media (min-width: 640px) { .cap-grid { grid-template-columns: repeat(2, 1fr); } }
@media (min-width: 900px) { .cap-grid { grid-template-columns: repeat(3, 1fr); } }
.cap-card {
  padding: 24px; background: var(--bg-elevated); border: 1px solid var(--border);
  border-radius: 12px; transition: all var(--transition);
}
.cap-card:hover { border-color: var(--accent); }
.cap-icon { font-size: 1.5rem; margin-bottom: 12px; }
.cap-card h3 { font-size: 0.9375rem; font-weight: 700; margin-bottom: 12px; }
.cap-list { list-style: none; }
.cap-list li {
  font-size: 0.8125rem; color: var(--text-secondary); padding: 3px 0;
  padding-left: 16px; position: relative;
}
.cap-list li::before {
  content: ''; position: absolute; left: 0; top: 11px;
  width: 6px; height: 6px; border-radius: 50%; background: var(--accent-light);
  border: 1px solid var(--accent);
}

/* ---- ARCHITECTURE DIAGRAM ---- */
.arch-diagram {
  display: flex; flex-direction: column; align-items: center;
  gap: 0; padding: 32px 0;
}
.arch-node {
  padding: 12px 28px; background: var(--bg-elevated); border: 1px solid var(--border);
  border-radius: 8px; font-size: 0.8125rem; font-weight: 600;
  color: var(--text-primary); text-align: center; min-width: 200px;
  transition: all var(--transition);
}
.arch-node:hover { border-color: var(--accent); background: var(--accent-subtle); }
.arch-node.accent { background: var(--accent); color: #fff; border-color: var(--accent); }
.arch-arrow {
  width: 1px; height: 28px; background: var(--border); position: relative;
}
.arch-arrow::after {
  content: ''; position: absolute; bottom: 0; left: -4px;
  border-left: 5px solid transparent; border-right: 5px solid transparent;
  border-top: 6px solid var(--border);
}

/* ---- PHILOSOPHY ---- */
.philosophy-grid { display: grid; gap: 0; counter-reset: phil; }
@media (min-width: 768px) { .philosophy-grid { grid-template-columns: repeat(2, 1fr); } }
.phil-item {
  padding: 20px 0; border-bottom: 1px solid var(--border-light);
  display: flex; gap: 16px; align-items: flex-start; counter-increment: phil;
}
.phil-num {
  font-size: 0.75rem; font-weight: 700; color: var(--text-tertiary);
  min-width: 28px; padding-top: 2px; font-variant-numeric: tabular-nums;
}
.phil-item p { font-size: 0.875rem; color: var(--text-secondary); }

/* ---- TECH STACK ---- */
.stack-section { margin-bottom: 28px; }
.stack-label { font-size: 0.75rem; font-weight: 600; color: var(--text-tertiary); text-transform: uppercase; letter-spacing: 0.06em; margin-bottom: 10px; }
.stack-items { display: flex; flex-wrap: wrap; gap: 8px; }
.stack-item {
  font-size: 0.8125rem; font-weight: 500; padding: 6px 14px;
  background: var(--bg-alt); border: 1px solid var(--border);
  border-radius: 6px; color: var(--text-primary); transition: all var(--transition);
}
.stack-item:hover { border-color: var(--accent); color: var(--accent); }

/* ---- EDUCATION ---- */
.edu-card {
  display: flex; gap: 20px; align-items: flex-start;
  padding: 24px; background: var(--bg-alt); border-radius: 12px;
  border: 1px solid var(--border-light);
}
.edu-icon { font-size: 2rem; }
.edu-card h3 { font-size: 1rem; font-weight: 700; margin-bottom: 4px; }
.edu-card p { font-size: 0.875rem; color: var(--text-secondary); }

/* ---- CONTACT ---- */
.contact-section { background: var(--bg-alt); border-radius: 16px; padding: 48px; text-align: center; }
@media (max-width: 767px) { .contact-section { padding: 32px 20px; } }
.contact-section h2 { font-size: 1.75rem; font-weight: 700; margin-bottom: 16px; }
.contact-section p { font-size: 0.9375rem; color: var(--text-secondary); max-width: 560px; margin: 0 auto 32px; line-height: 1.7; }
.contact-btns { display: flex; flex-wrap: wrap; gap: 12px; justify-content: center; }

/* ---- FOOTER ---- */
.footer { border-top: 1px solid var(--border); padding: 40px 0; }
.footer-inner {
  display: flex; flex-direction: column; gap: 24px;
  align-items: center; text-align: center;
}
@media (min-width: 768px) { .footer-inner { flex-direction: row; justify-content: space-between; text-align: left; } }
.footer-brand p { font-size: 0.8125rem; color: var(--text-tertiary); margin-top: 4px; }
.footer-links { display: flex; gap: 20px; }
.footer-links a {
  font-size: 0.8125rem; color: var(--text-tertiary); text-decoration: none;
  transition: color var(--transition);
}
.footer-links a:hover { color: var(--accent); }
.footer-copy { font-size: 0.75rem; color: var(--text-tertiary); text-align: center; margin-top: 24px; padding-top: 24px; border-top: 1px solid var(--border-light); }

/* ---- BACK TO TOP ---- */
.back-to-top {
  position: fixed; bottom: 24px; right: 24px; width: 40px; height: 40px;
  background: var(--accent); color: #fff; border: none; border-radius: 10px;
  cursor: pointer; display: flex; align-items: center; justify-content: center;
  opacity: 0; visibility: hidden; transition: all var(--transition);
  box-shadow: 0 4px 12px rgba(37,99,235,0.25); z-index: 50;
}
.back-to-top.visible { opacity: 1; visibility: visible; }
.back-to-top:hover { transform: translateY(-2px); }
.back-to-top svg { width: 20px; height: 20px; }

/* ---- ANIMATIONS ---- */
.fade-up {
  opacity: 0; transform: translateY(20px);
  transition: opacity 0.5s ease, transform 0.5s ease;
}
.fade-up.visible { opacity: 1; transform: translateY(0); }

/* Respect reduced motion */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: 0.01ms !important; transition-duration: 0.01ms !important; }
  html { scroll-behavior: auto; }
  .fade-up { opacity: 1; transform: none; }
}

/* ---- GITHUB SECTION ---- */
.github-card {
  display: flex; align-items: center; gap: 20px;
  padding: 24px; background: var(--bg-alt); border: 1px solid var(--border);
  border-radius: 12px;
}
.github-card img { width: 48px; height: 48px; border-radius: 8px; }
.github-info h3 { font-size: 1rem; font-weight: 700; margin-bottom: 4px; }
.github-info p { font-size: 0.8125rem; color: var(--text-secondary); }

/* ---- EMAIL TOAST ---- */
.toast {
  position: fixed; bottom: 24px; left: 50%; transform: translateX(-50%);
  background: var(--text-primary); color: var(--bg); padding: 12px 24px;
  border-radius: 8px; font-size: 0.875rem; font-weight: 500;
  opacity: 0; visibility: hidden; transition: all 0.3s ease; z-index: 200;
  display: flex; align-items: center; gap: 8px;
}
.toast.show { opacity: 1; visibility: visible; }

/* ---- INFRA DIAGRAM GRID ---- */
.infra-grid { display: grid; gap: 20px; }
@media (min-width: 768px) { .infra-grid { grid-template-columns: repeat(2, 1fr); } }
.infra-item {
  padding: 20px; background: var(--bg-elevated); border: 1px solid var(--border);
  border-radius: 10px; display: flex; align-items: flex-start; gap: 14px;
}
.infra-item .infra-icon { font-size: 1.25rem; min-width: 28px; text-align: center; }
.infra-item h4 { font-size: 0.875rem; font-weight: 700; margin-bottom: 4px; }
.infra-item p { font-size: 0.8125rem; color: var(--text-secondary); }

/* ---- DB SECTION ---- */
.db-capabilities { display: grid; gap: 12px; }
@media (min-width: 640px) { .db-capabilities { grid-template-columns: repeat(2, 1fr); } }
@media (min-width: 900px) { .db-capabilities { grid-template-columns: repeat(3, 1fr); } }
.db-cap {
  padding: 16px; background: var(--bg-alt); border-radius: 8px;
  border: 1px solid var(--border-light); font-size: 0.8125rem;
  font-weight: 500; color: var(--text-secondary); text-align: center;
  transition: all var(--transition);
}
.db-cap:hover { border-color: var(--accent); color: var(--accent); }

/* Print styles */
@media print {
  .nav, .back-to-top, .mobile-menu, .theme-toggle { display: none !important; }
  section { padding: 24px 0; }
  body { color: #000; background: #fff; }
}