/* ============================================================
   CSS Custom Properties
   ============================================================ */
:root {
  --color-primary: #0070f3;
  --color-primary-dark: #0051b5;
  --color-accent: #00c9a7;
  --color-bg: #f8fafc;
  --color-bg-white: #ffffff;
  --color-bg-card: #ffffff;
  --color-text: #1a202c;
  --color-text-muted: #64748b;
  --color-border: #e2e8f0;
  --color-hero-bg: #0f172a;
  --color-hero-text: #f1f5f9;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: "JetBrains Mono", "Fira Code", "Cascadia Code", Consolas, monospace;
  --radius: 8px;
  --shadow: 0 2px 12px rgba(0, 0, 0, 0.08);
  --shadow-hover: 0 6px 24px rgba(0, 0, 0, 0.12);
  --max-width: 1200px;
  --transition: 0.2s ease;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.7;
  font-size: 16px;
}

img {
  max-width: 100%;
  height: auto;
  border-radius: var(--radius);
}

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

a:hover {
  color: var(--color-primary-dark);
}

ul {
  list-style: none;
}

/* ============================================================
   Layout
   ============================================================ */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

/* ============================================================
   Header / Navigation
   ============================================================ */
.site-header {
  background: var(--color-bg-white);
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.06);
}

.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.logo {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--color-text);
  letter-spacing: -0.5px;
}

.logo:hover {
  color: var(--color-primary);
}

nav {
  display: flex;
  align-items: center;
  gap: 8px;
}

nav a {
  color: var(--color-text-muted);
  font-weight: 500;
  padding: 8px 12px;
  border-radius: var(--radius);
  transition: background var(--transition), color var(--transition);
}

nav a:hover {
  background: var(--color-bg);
  color: var(--color-text);
}

.btn-contact {
  background: var(--color-primary) !important;
  color: #fff !important;
  padding: 8px 20px !important;
  border-radius: 999px !important;
}

.btn-contact:hover {
  background: var(--color-primary-dark) !important;
}

nav a.active {
  color: var(--color-primary);
  background: #eff6ff;
}

/* ============================================================
   Hero Section
   ============================================================ */
.hero {
  background: var(--color-hero-bg);
  color: var(--color-hero-text);
  padding: 80px 0 60px;
}

.hero .container {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 48px;
  align-items: center;
}

.hero-badge {
  display: inline-block;
  background: rgba(0, 201, 167, 0.15);
  color: var(--color-accent);
  font-size: 0.875rem;
  font-weight: 600;
  padding: 6px 14px;
  border-radius: 999px;
  margin-bottom: 16px;
  border: 1px solid rgba(0, 201, 167, 0.3);
}

.hero h1 {
  font-size: clamp(2rem, 4vw, 3rem);
  font-weight: 800;
  line-height: 1.2;
  letter-spacing: -1px;
  margin-bottom: 16px;
}

.hero-subtitle {
  font-size: 1.125rem;
  color: #94a3b8;
  max-width: 520px;
  margin-bottom: 32px;
}

.hero-actions {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.btn-primary {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: var(--color-primary);
  color: #fff;
  padding: 12px 24px;
  border-radius: 999px;
  font-weight: 600;
  font-size: 0.9375rem;
  transition: background var(--transition), transform var(--transition);
}

.btn-primary:hover {
  background: var(--color-primary-dark);
  color: #fff;
  transform: translateY(-1px);
}

.btn-secondary {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: rgba(255, 255, 255, 0.08);
  color: var(--color-hero-text);
  padding: 12px 24px;
  border-radius: 999px;
  font-weight: 600;
  font-size: 0.9375rem;
  border: 1px solid rgba(255, 255, 255, 0.15);
  transition: background var(--transition);
}

.btn-secondary:hover {
  background: rgba(255, 255, 255, 0.14);
  color: var(--color-hero-text);
}

.hero-avatar {
  width: 140px;
  height: 140px;
  border-radius: 50%;
  border: 4px solid rgba(255, 255, 255, 0.1);
  overflow: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.hero-avatar img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: center 20%;
}

/* ============================================================
   Sections
   ============================================================ */
.section {
  padding: 72px 0;
}

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

.section-title {
  font-size: 1.875rem;
  font-weight: 700;
  letter-spacing: -0.5px;
  margin-bottom: 12px;
}

.section-lead {
  color: var(--color-text-muted);
  font-size: 1.0625rem;
  max-width: 600px;
  margin-bottom: 40px;
}

/* ============================================================
   About Section
   ============================================================ */
.about-content {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 48px;
  align-items: start;
}

.about-text p {
  margin-bottom: 16px;
  color: var(--color-text-muted);
  line-height: 1.8;
}

.about-text p:first-child {
  font-size: 1.0625rem;
  color: var(--color-text);
}

/* ============================================================
   Value Cards
   ============================================================ */
.value-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 20px;
  margin-top: 8px;
}

.value-card {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 24px;
  transition: box-shadow var(--transition), transform var(--transition);
}

.value-card:hover {
  box-shadow: var(--shadow-hover);
  transform: translateY(-2px);
}

.value-icon {
  font-size: 1.75rem;
  margin-bottom: 12px;
}

.value-card h3 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 8px;
}

.value-card p {
  font-size: 0.9rem;
  color: var(--color-text-muted);
  line-height: 1.6;
}

/* ============================================================
   Tech Stack
   ============================================================ */
.tech-stack {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 24px;
}

.tech-category h3 {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--color-text-muted);
  margin-bottom: 12px;
}

.tech-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.tech-tag {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  color: var(--color-text);
  font-size: 0.8125rem;
  font-weight: 500;
  padding: 4px 12px;
  border-radius: 999px;
}

/* ============================================================
   Project Cards
   ============================================================ */
.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
  gap: 24px;
  max-width: 900px;
  margin: 0 auto;
}

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

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

.project-card-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 12px;
}

.project-card h3 {
  font-size: 1.125rem;
  font-weight: 700;
}

.project-status {
  font-size: 0.75rem;
  font-weight: 600;
  padding: 3px 10px;
  border-radius: 999px;
  white-space: nowrap;
  flex-shrink: 0;
}

.status-completed {
  background: #dcfce7;
  color: #16a34a;
}

.status-ongoing {
  background: #dbeafe;
  color: #2563eb;
}

.status-confidential {
  background: #fef9c3;
  color: #a16207;
}

.project-meta {
  display: flex;
  flex-direction: column;
  gap: 4px;
  font-size: 0.8125rem;
  color: var(--color-text-muted);
}

.project-card p {
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  line-height: 1.6;
  flex: 1;
}

.project-tech {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-top: 4px;
}

.project-tech span {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  font-size: 0.75rem;
  font-weight: 500;
  padding: 2px 10px;
  border-radius: 999px;
  color: var(--color-text-muted);
}

/* ============================================================
   Articles
   ============================================================ */
.articles-list {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.article-card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 28px;
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 16px;
  align-items: center;
  box-shadow: var(--shadow);
  transition: box-shadow var(--transition), transform var(--transition);
}

.article-card:hover {
  box-shadow: var(--shadow-hover);
  transform: translateX(4px);
}

.article-card-body h3 {
  font-size: 1.1875rem;
  font-weight: 700;
  margin-bottom: 6px;
}

.article-card-body h3 a {
  color: var(--color-text);
}

.article-card-body h3 a:hover {
  color: var(--color-primary);
}

.article-card-body p {
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  line-height: 1.5;
  margin-bottom: 12px;
}

.article-meta {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
}

.article-date {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
}

.article-tags {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
}

.tag {
  font-size: 0.75rem;
  font-weight: 600;
  padding: 2px 10px;
  border-radius: 999px;
  background: #e0f2fe;
  color: #0369a1;
}

.article-arrow {
  font-size: 1.5rem;
  color: var(--color-border);
  transition: color var(--transition), transform var(--transition);
}

.article-card:hover .article-arrow {
  color: var(--color-primary);
  transform: translateX(4px);
}

.empty-state {
  text-align: center;
  padding: 60px 24px;
  color: var(--color-text-muted);
}

.empty-state p {
  font-size: 1.0625rem;
}

/* ============================================================
   Article Page
   ============================================================ */
.article-page {
  padding: 48px 0 80px;
}

.article-header {
  margin-bottom: 40px;
  padding-bottom: 32px;
  border-bottom: 1px solid var(--color-border);
}

.article-header h1 {
  font-size: clamp(1.75rem, 3vw, 2.5rem);
  font-weight: 800;
  letter-spacing: -0.5px;
  line-height: 1.25;
  margin-top: 16px;
  margin-bottom: 12px;
}

.article-lead {
  font-size: 1.125rem;
  color: var(--color-text-muted);
  line-height: 1.6;
  margin-top: 8px;
}

.article-body {
  max-width: 780px;
}

.article-body h2 {
  font-size: 1.5rem;
  font-weight: 700;
  margin-top: 40px;
  margin-bottom: 16px;
  letter-spacing: -0.25px;
}

.article-body h3 {
  font-size: 1.25rem;
  font-weight: 600;
  margin-top: 32px;
  margin-bottom: 12px;
}

.article-body p {
  margin-bottom: 20px;
  line-height: 1.8;
}

.article-body ul,
.article-body ol {
  margin-bottom: 20px;
  padding-left: 24px;
}

.article-body ul {
  list-style: disc;
}

.article-body ol {
  list-style: decimal;
}

.article-body li {
  margin-bottom: 6px;
  line-height: 1.7;
}

.article-body code {
  font-family: var(--font-mono);
  font-size: 0.875em;
  background: #f1f5f9;
  padding: 2px 6px;
  border-radius: 4px;
  color: #0f172a;
}

.article-body pre {
  background: #0f172a;
  color: #e2e8f0;
  padding: 20px 24px;
  border-radius: var(--radius);
  overflow-x: auto;
  margin-bottom: 24px;
  font-family: var(--font-mono);
  font-size: 0.875rem;
  line-height: 1.7;
}

.article-body pre code {
  background: transparent;
  padding: 0;
  color: inherit;
}

.article-body blockquote {
  border-left: 4px solid var(--color-primary);
  padding: 12px 20px;
  margin: 24px 0;
  background: #eff6ff;
  border-radius: 0 var(--radius) var(--radius) 0;
  color: var(--color-text-muted);
}

.article-body img {
  margin: 24px 0;
  box-shadow: var(--shadow);
}

.article-body .mermaid {
  margin: 28px 0;
  text-align: center;
}

.article-footer {
  margin-top: 56px;
  padding-top: 24px;
  border-top: 1px solid var(--color-border);
}

.btn-back {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: var(--color-text-muted);
  font-weight: 500;
  font-size: 0.9375rem;
  padding: 8px 0;
  border-radius: var(--radius);
  transition: color var(--transition);
}

.btn-back:hover {
  color: var(--color-primary);
}

/* ============================================================
   Page Hero (inner pages)
   ============================================================ */
.page-hero {
  background: var(--color-hero-bg);
  color: var(--color-hero-text);
  padding: 56px 0;
}

.page-hero h1 {
  font-size: clamp(1.75rem, 3vw, 2.5rem);
  font-weight: 800;
  letter-spacing: -0.5px;
  margin-bottom: 10px;
}

.page-hero p {
  color: #94a3b8;
  font-size: 1.0625rem;
  max-width: 560px;
}

/* ============================================================
   Availability Banner
   ============================================================ */
.availability-banner {
  background: linear-gradient(135deg, #0070f3 0%, #00c9a7 100%);
  color: #fff;
  padding: 48px 0;
  text-align: center;
}

.availability-banner h2 {
  font-size: 1.75rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.availability-banner p {
  font-size: 1.0625rem;
  opacity: 0.9;
  margin-bottom: 24px;
}

.btn-white {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: #fff;
  color: var(--color-primary);
  padding: 12px 28px;
  border-radius: 999px;
  font-weight: 700;
  font-size: 0.9375rem;
  transition: transform var(--transition), box-shadow var(--transition);
}

.btn-white:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.15);
  color: var(--color-primary-dark);
}

/* ============================================================
   Footer
   ============================================================ */
.site-footer {
  background: var(--color-hero-bg);
  color: #94a3b8;
  padding: 48px 0 24px;
}

.footer-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 32px;
  padding-bottom: 32px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.06);
  margin-bottom: 24px;
}

.site-footer h4 {
  font-size: 0.875rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.8px;
  color: #e2e8f0;
  margin-bottom: 14px;
}

.site-footer p {
  font-size: 0.9rem;
  line-height: 1.6;
}

.site-footer ul li {
  margin-bottom: 8px;
}

.site-footer a {
  color: #94a3b8;
  font-size: 0.9rem;
  transition: color var(--transition);
}

.site-footer a:hover {
  color: #e2e8f0;
}

.footer-copy {
  font-size: 0.8125rem;
  text-align: center;
}

/* ============================================================
   Responsive
   ============================================================ */
@media (max-width: 768px) {
  .hero .container {
    grid-template-columns: 1fr;
  }

  .hero-avatar {
    display: none;
  }

  .about-content {
    grid-template-columns: 1fr;
  }

  .article-card {
    grid-template-columns: 1fr;
  }

  .article-arrow {
    display: none;
  }

  nav a:not(.btn-contact) {
    display: none;
  }

  nav {
    gap: 4px;
  }
}

@media (max-width: 480px) {
  .projects-grid {
    grid-template-columns: 1fr;
  }

  .hero-actions {
    flex-direction: column;
  }
}