/* ============================================
   Modern Design System — Kulin Seth
   Clean, minimal, elegant
   ============================================ */

/* --- CSS Custom Properties --- */
:root {
  --color-bg: #fafafa;
  --color-surface: #ffffff;
  --color-text: #1a1a2e;
  --color-text-secondary: #555770;
  --color-text-muted: #8b8da3;
  --color-accent: #2563eb;
  --color-accent-hover: #1d4ed8;
  --color-border: #e5e7eb;
  --color-border-light: #f0f0f5;
  --color-tag-bg: #f1f5f9;
  --color-tag-text: #475569;
  --color-code-bg: #f8f9fc;

  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'SF Mono', monospace;

  --max-width: 720px;
  --max-width-wide: 900px;
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2.5rem;
  --space-2xl: 4rem;
  --space-3xl: 6rem;

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-full: 50%;

  --shadow-sm: 0 1px 2px rgba(0,0,0,0.04);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.06);
  --shadow-lg: 0 8px 30px rgba(0,0,0,0.08);

  --transition: 0.2s ease;
}

/* --- Reset & Base --- */
*, *::before, *::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.7;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* --- Typography --- */
h1, h2, h3, h4 {
  font-weight: 600;
  line-height: 1.3;
  letter-spacing: -0.02em;
}

h1 {
  font-size: 2.25rem;
}

h2 {
  font-size: 1.5rem;
  margin-bottom: var(--space-lg);
}

h3 {
  font-size: 1.125rem;
  margin-bottom: var(--space-sm);
}

p {
  margin-bottom: var(--space-md);
  color: var(--color-text-secondary);
}

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

a:hover {
  color: var(--color-accent-hover);
}

strong {
  font-weight: 600;
  color: var(--color-text);
}

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

.container--wide {
  max-width: var(--max-width-wide);
}

main {
  flex: 1;
}

/* --- Navigation --- */
.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(250, 250, 250, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border-light);
}

.nav__inner {
  max-width: var(--max-width-wide);
  margin: 0 auto;
  padding: 0 var(--space-lg);
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 60px;
}

.nav__brand {
  font-weight: 600;
  font-size: 1.05rem;
  color: var(--color-text);
  letter-spacing: -0.01em;
}

.nav__brand:hover {
  color: var(--color-text);
}

.nav__links {
  display: flex;
  gap: var(--space-lg);
  list-style: none;
}

.nav__links a {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  font-weight: 450;
  padding: var(--space-xs) 0;
  position: relative;
  transition: color var(--transition);
}

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

.nav__links a.active::after {
  content: '';
  position: absolute;
  bottom: -2px;
  left: 0;
  right: 0;
  height: 2px;
  background: var(--color-accent);
  border-radius: 1px;
}

/* Mobile nav toggle */
.nav__toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--space-sm);
}

.nav__toggle span {
  display: block;
  width: 20px;
  height: 2px;
  background: var(--color-text);
  margin: 4px 0;
  transition: var(--transition);
}

/* --- Hero / Page Header --- */
.hero {
  padding: var(--space-3xl) 0 var(--space-2xl);
}

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

.hero__photo {
  width: 140px;
  height: 140px;
  border-radius: var(--radius-full);
  object-fit: cover;
  flex-shrink: 0;
  border: 3px solid var(--color-border-light);
}

.hero__content {
  flex: 1;
}

.hero__greeting {
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--color-accent);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: var(--space-sm);
}

.hero__title {
  font-size: 2.5rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  margin-bottom: var(--space-md);
  color: var(--color-text);
}

.hero__subtitle {
  font-size: 1.125rem;
  color: var(--color-text-secondary);
  line-height: 1.7;
  max-width: 520px;
}

.page-header {
  padding: var(--space-2xl) 0 var(--space-xl);
  border-bottom: 1px solid var(--color-border);
  margin-bottom: var(--space-2xl);
}

.page-header h1 {
  margin-bottom: var(--space-sm);
}

.page-header p {
  font-size: 1.05rem;
  color: var(--color-text-muted);
}

/* --- Tags / Chips --- */
.tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  margin-top: var(--space-lg);
}

.tag {
  display: inline-block;
  font-size: 0.8rem;
  font-weight: 500;
  padding: 0.3em 0.8em;
  background: var(--color-tag-bg);
  color: var(--color-tag-text);
  border-radius: var(--radius-sm);
  letter-spacing: 0.01em;
}

/* --- Sections --- */
.section {
  padding: var(--space-2xl) 0;
}

.section + .section {
  border-top: 1px solid var(--color-border-light);
}

.section__title {
  font-size: 0.8rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--color-text-muted);
  margin-bottom: var(--space-xl);
}

/* --- Cards --- */
.card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  transition: box-shadow var(--transition), border-color var(--transition);
}

.card:hover {
  box-shadow: var(--shadow-md);
  border-color: transparent;
}

.card + .card {
  margin-top: var(--space-md);
}

.card__header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: var(--space-sm);
  gap: var(--space-md);
}

.card__title {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--color-text);
}

.card__meta {
  font-size: 0.8rem;
  color: var(--color-text-muted);
  white-space: nowrap;
  flex-shrink: 0;
}

.card__subtitle {
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--color-accent);
  margin-bottom: var(--space-sm);
}

.card__body {
  font-size: 0.92rem;
  color: var(--color-text-secondary);
  line-height: 1.7;
}

.card__body ul {
  margin: var(--space-sm) 0;
  padding-left: var(--space-lg);
}

.card__body li {
  margin-bottom: var(--space-xs);
  color: var(--color-text-secondary);
  font-size: 0.9rem;
}

/* --- Project Grid --- */
.project-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-md);
}

.project-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  transition: all var(--transition);
  display: flex;
  flex-direction: column;
}

.project-card:hover {
  box-shadow: var(--shadow-md);
  border-color: transparent;
  transform: translateY(-2px);
}

.project-card__title {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: var(--space-sm);
  color: var(--color-text);
}

.project-card__title a {
  color: inherit;
}

.project-card__title a:hover {
  color: var(--color-accent);
}

.project-card__desc {
  font-size: 0.87rem;
  color: var(--color-text-secondary);
  line-height: 1.6;
  flex: 1;
}

.project-card__tags {
  margin-top: var(--space-md);
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-xs);
}

.project-card__tag {
  font-size: 0.72rem;
  font-weight: 500;
  padding: 0.2em 0.6em;
  background: var(--color-tag-bg);
  color: var(--color-tag-text);
  border-radius: 4px;
}

/* --- Skills Grid --- */
.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: var(--space-md);
}

.skill-group {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
}

.skill-group__title {
  font-size: 0.8rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-text-muted);
  margin-bottom: var(--space-md);
}

.skill-group__list {
  list-style: none;
}

.skill-group__list li {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  padding: var(--space-xs) 0;
}

/* --- Timeline (CV) --- */
.timeline-item {
  position: relative;
  padding-left: var(--space-xl);
  padding-bottom: var(--space-2xl);
}

.timeline-item::before {
  content: '';
  position: absolute;
  left: 0;
  top: 8px;
  width: 8px;
  height: 8px;
  background: var(--color-accent);
  border-radius: var(--radius-full);
}

.timeline-item::after {
  content: '';
  position: absolute;
  left: 3.5px;
  top: 20px;
  bottom: 0;
  width: 1px;
  background: var(--color-border);
}

.timeline-item:last-child::after {
  display: none;
}

.timeline-item:last-child {
  padding-bottom: 0;
}

/* --- Blog --- */
.blog-post {
  padding: var(--space-xl) 0;
}

.blog-post + .blog-post {
  border-top: 1px solid var(--color-border-light);
}

.blog-post__date {
  font-size: 0.8rem;
  color: var(--color-text-muted);
  font-weight: 500;
  margin-bottom: var(--space-sm);
}

.blog-post__title {
  font-size: 1.35rem;
  font-weight: 600;
  margin-bottom: var(--space-sm);
}

.blog-post__excerpt {
  font-size: 0.95rem;
  color: var(--color-text-secondary);
}

.blog-empty {
  text-align: center;
  padding: var(--space-3xl) 0;
}

.blog-empty__icon {
  font-size: 3rem;
  margin-bottom: var(--space-md);
  opacity: 0.3;
}

.blog-empty__text {
  font-size: 1.1rem;
  color: var(--color-text-muted);
}

/* --- Contact --- */
.contact-section {
  text-align: center;
  padding: var(--space-3xl) 0;
}

.contact-section h1 {
  margin-bottom: var(--space-md);
}

.contact-links {
  display: flex;
  justify-content: center;
  gap: var(--space-xl);
  margin-top: var(--space-xl);
}

.contact-link {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-sm);
  color: var(--color-text-secondary);
  font-size: 0.95rem;
  transition: color var(--transition);
  padding: var(--space-lg);
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
  min-width: 160px;
}

.contact-link:hover {
  color: var(--color-accent);
  border-color: var(--color-accent);
  background: rgba(37, 99, 235, 0.03);
}

.contact-link svg {
  width: 28px;
  height: 28px;
  stroke: currentColor;
  fill: none;
  stroke-width: 1.5;
}

/* --- Footer --- */
.footer {
  margin-top: auto;
  padding: var(--space-xl) 0;
  border-top: 1px solid var(--color-border-light);
}

.footer__inner {
  max-width: var(--max-width-wide);
  margin: 0 auto;
  padding: 0 var(--space-lg);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.footer__text {
  font-size: 0.82rem;
  color: var(--color-text-muted);
  margin: 0;
}

.footer__links {
  display: flex;
  gap: var(--space-lg);
  list-style: none;
}

.footer__links a {
  font-size: 0.82rem;
  color: var(--color-text-muted);
}

.footer__links a:hover {
  color: var(--color-text);
}

/* --- Utilities --- */
.text-center { text-align: center; }
.mt-sm { margin-top: var(--space-sm); }
.mt-md { margin-top: var(--space-md); }
.mt-lg { margin-top: var(--space-lg); }
.mt-xl { margin-top: var(--space-xl); }
.mb-md { margin-bottom: var(--space-md); }
.mb-lg { margin-bottom: var(--space-lg); }

/* --- Animations --- */
@keyframes fadeUp {
  from {
    opacity: 0;
    transform: translateY(16px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.fade-up {
  animation: fadeUp 0.6s ease forwards;
}

.fade-up-delay-1 { animation-delay: 0.1s; opacity: 0; }
.fade-up-delay-2 { animation-delay: 0.2s; opacity: 0; }
.fade-up-delay-3 { animation-delay: 0.3s; opacity: 0; }

/* --- Responsive --- */
@media (max-width: 768px) {
  .hero--home {
    flex-direction: column;
    text-align: center;
    gap: var(--space-lg);
  }

  .hero__title {
    font-size: 2rem;
  }

  .hero__subtitle {
    max-width: 100%;
  }

  .tags {
    justify-content: center;
  }

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

  .card__header {
    flex-direction: column;
    gap: var(--space-xs);
  }

  .contact-links {
    flex-direction: column;
    align-items: center;
  }

  .footer__inner {
    flex-direction: column;
    gap: var(--space-md);
    text-align: center;
  }
}

@media (max-width: 480px) {
  html {
    font-size: 15px;
  }

  .nav__links {
    display: none;
    position: absolute;
    top: 60px;
    left: 0;
    right: 0;
    background: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    flex-direction: column;
    padding: var(--space-md) var(--space-lg);
    gap: var(--space-sm);
  }

  .nav__links.open {
    display: flex;
  }

  .nav__toggle {
    display: block;
  }

  .hero__photo {
    width: 110px;
    height: 110px;
  }

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

/* --- Print --- */
@media print {
  .nav, .footer { display: none; }
  body { background: white; }
  .container { max-width: 100%; }
  .card { border: 1px solid #ddd; box-shadow: none; }
}