/* ========================================
   Design System - CSS Custom Properties
   ======================================== */

:root {
  /* Colors */
  --color-primary: #1165C4;
  --color-primary-dark: #0D50A0;
  --color-primary-light: #E3ECFB;

  --color-text: #555555;
  --color-text-secondary: #666666;
  --color-text-muted: #888888;

  --color-background: #FFFFFF;
  --color-background-alt: #F8F8F8;
  --color-border: #E5E7EB;

  --color-success: #2E7D32;
  --color-warning: #D97706;
  --color-error: #DC2626;

  /* Typography */
  --font-family-base: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto,
                      Oxygen-Sans, Ubuntu, Cantarell, 'Helvetica Neue', sans-serif;
  --font-size-base: 16px;
  --font-size-sm: 0.875rem;
  --font-size-lg: 1.125rem;

  --line-height-base: 1.5;
  --line-height-heading: 1.25;

  /* Spacing */
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2rem;
  --spacing-2xl: 3rem;
  --spacing-3xl: 4rem;

  /* Focus */
  --focus-outline-width: 3px;
  --focus-outline-offset: 2px;
  --color-focus: #0052CC;

  /* Container */
  --container-max-width: 1200px;
  --container-padding: 1rem;

  /* Transitions */
  --transition-base: 0.2s ease;

  /* Border Radius */
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;

  /* Shadows */
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.1);
  --shadow-md: 0 2px 8px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 4px 16px rgba(0, 0, 0, 0.1);
}

/* ========================================
   CSS Reset & Base Styles
   ======================================== */

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

* {
  margin: 0;
  padding: 0;
}

html {
  font-size: var(--font-size-base);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-family-base);
  font-size: var(--font-size-base);
  line-height: var(--line-height-base);
  color: var(--color-text);
  background-color: var(--color-background);
}

/* ========================================
   Typography
   ======================================== */

h1, h2, h3, h4, h5, h6 {
  line-height: var(--line-height-heading);
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: var(--spacing-md);
}

h1 {
  font-size: clamp(2.25rem, 5vw, 3rem);
}

h2 {
  font-size: clamp(1.75rem, 4vw, 2.25rem);
}

h3 {
  font-size: clamp(1.25rem, 3vw, 1.5rem);
}

p {
  margin-bottom: var(--spacing-md);
}

a {
  color: var(--color-primary);
  text-decoration: underline;
  transition: color var(--transition-base);
}

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

a:focus {
  outline: none;
}

a:focus-visible {
  outline: var(--focus-outline-width) solid var(--color-focus);
  outline-offset: var(--focus-outline-offset);
}

ul, ol {
  list-style-position: outside;
  margin-left: var(--spacing-lg);
  margin-bottom: var(--spacing-md);
}

/* ========================================
   Accessibility Utilities
   ======================================== */

/* Skip Link */
.skip-link {
  position: absolute;
  top: -100px;
  left: 0;
  padding: var(--spacing-md) var(--spacing-lg);
  background: var(--color-primary);
  color: white;
  text-decoration: none;
  font-weight: 700;
  z-index: 100;
  border-radius: 0 0 var(--radius-md) 0;
}

.skip-link:focus {
  top: 0;
  outline: none;
}

/* Screen Reader Only */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* Focus Visible (keyboard only) */
*:focus {
  outline: none;
}

*:focus-visible {
  outline: var(--focus-outline-width) solid var(--color-focus);
  outline-offset: var(--focus-outline-offset);
}

/* Reduced Motion */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

/* ========================================
   Layout - Container
   ======================================== */

.container {
  max-width: var(--container-max-width);
  margin-left: auto;
  margin-right: auto;
  padding-left: var(--container-padding);
  padding-right: var(--container-padding);
}

@media (min-width: 768px) {
  .container {
    --container-padding: 2rem;
  }
}

/* ========================================
   Header
   ======================================== */

.site-header {
  background: var(--color-background);
  border-bottom: 1px solid var(--color-border);
  padding: var(--spacing-lg) 0;
  position: sticky;
  top: 0;
  z-index: 50;
}

.header-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.site-title {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--color-text);
  text-decoration: none;
}

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

/* Mobile Menu Toggle */
.mobile-menu-toggle {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  width: 44px;
  height: 44px;
  padding: var(--spacing-sm);
  background: transparent;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: background-color var(--transition-base);
}

.mobile-menu-toggle:hover {
  background: var(--color-background-alt);
}

.menu-icon {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.menu-line {
  display: block;
  width: 20px;
  height: 2px;
  background: var(--color-text);
  transition: transform var(--transition-base);
}

.mobile-menu-toggle[aria-expanded="true"] .menu-line:nth-child(1) {
  transform: translateY(6px) rotate(45deg);
}

.mobile-menu-toggle[aria-expanded="true"] .menu-line:nth-child(2) {
  opacity: 0;
}

.mobile-menu-toggle[aria-expanded="true"] .menu-line:nth-child(3) {
  transform: translateY(-6px) rotate(-45deg);
}

/* Primary Navigation */
.primary-nav {
  display: none;
}

.primary-nav.is-open {
  display: block;
  position: absolute;
  top: 100%;
  left: 0;
  right: 0;
  background: var(--color-background);
  border-bottom: 1px solid var(--color-border);
  padding: var(--spacing-md) 0;
}

.nav-menu {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-sm);
  list-style: none;
  margin: 0;
}

.nav-link {
  display: block;
  padding: var(--spacing-sm) var(--spacing-md);
  color: var(--color-text);
  text-decoration: none;
  font-weight: 500;
  transition: color var(--transition-base);
}

.nav-link:hover,
.nav-link.active {
  color: var(--color-primary);
}

.nav-link.active {
  font-weight: 700;
}

@media (min-width: 768px) {
  .mobile-menu-toggle {
    display: none;
  }

  .primary-nav {
    display: block;
    position: static;
    border: none;
    padding: 0;
  }

  .nav-menu {
    flex-direction: row;
    gap: var(--spacing-xl);
  }

  .nav-link {
    padding: var(--spacing-sm);
  }
}

/* ========================================
   Footer
   ======================================== */

.site-footer {
  border-top: 1px solid var(--color-border);
  padding: var(--spacing-xl) 0;
  text-align: center;
  margin-top: var(--spacing-3xl);
}

.footer-content {
  display: grid;
  gap: var(--spacing-xl);
  margin-bottom: var(--spacing-xl);
}

.footer-heading {
  font-size: 1.5rem;
  margin-bottom: var(--spacing-md);
}

.footer-subheading {
  font-size: 1.125rem;
  margin-bottom: var(--spacing-md);
}

.footer-intro {
  color: var(--color-text-secondary);
  max-width: 600px;
}

.contact-list,
.social-links {
  list-style: none;
  margin: 0;
}

.contact-item {
  margin-bottom: var(--spacing-sm);
}

.contact-label {
  font-weight: 600;
  color: var(--color-text-secondary);
  margin-right: var(--spacing-xs);
}

.contact-link {
  color: var(--color-primary);
}

.social-item {
  margin-bottom: var(--spacing-sm);
}

.social-link {
  color: var(--color-primary);
  font-weight: 500;
}

.footer-bottom {
  border-top: 1px solid var(--color-border);
  padding-top: var(--spacing-lg);
  text-align: center;
}

.copyright {
  color: var(--color-text-muted);
  font-size: var(--font-size-sm);
  margin: 0;
}

@media (min-width: 768px) {
  .footer-content {
    grid-template-columns: repeat(3, 1fr);
  }
}

/* ========================================
   Components - Buttons
   ======================================== */

.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.75rem 1.5rem;
  font-size: var(--font-size-base);
  font-weight: 600;
  line-height: 1;
  text-align: center;
  text-decoration: none;
  border-radius: var(--radius-md);
  border: 2px solid transparent;
  cursor: pointer;
  transition: all var(--transition-base);
  min-height: 44px;
}

.btn-primary {
  background: var(--color-primary);
  color: white;
  border-color: var(--color-primary);
}

.btn-primary:hover {
  background: var(--color-primary-dark);
  border-color: var(--color-primary-dark);
  color: white;
}

.btn-secondary {
  background: transparent;
  color: var(--color-primary);
  border-color: var(--color-primary);
}

.btn-secondary:hover {
  background: var(--color-primary);
  color: white;
}

.btn-lg {
  padding: 1rem 2rem;
  font-size: var(--font-size-lg);
}

/* ========================================
   Components - Cards
   ======================================== */

.card {
  background: var(--color-background);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--spacing-xl);
  transition: box-shadow var(--transition-base);
}

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

/* ========================================
   Components - Tags
   ======================================== */

.tag {
  display: inline-block;
  padding: var(--spacing-xs) var(--spacing-md);
  background: var(--color-background-alt);
  color: var(--color-text-secondary);
  font-size: var(--font-size-sm);
  font-weight: 500;
  border-radius: var(--radius-sm);
  margin-right: var(--spacing-xs);
  margin-bottom: var(--spacing-xs);
}

/* ========================================
   Hero Section
   ======================================== */

.hero {
  padding: var(--spacing-3xl) 0;
  background: var(--color-background);
  text-align: center;
}

.hero-photo {
  margin-bottom: var(--spacing-lg);
}

.hero-photo img {
  width: 140px;
  height: 140px;
  border-radius: 50%;
  object-fit: cover;
  object-position: center 15%;
  border: 3px solid var(--color-border);
  box-shadow: var(--shadow-sm);
}

.hero-content {
  max-width: 600px;
  margin: 0 auto;
}

.hero-title {
  font-size: clamp(2rem, 5vw, 3rem);
  margin-bottom: var(--spacing-md);
}

.hero-subtitle {
  display: block;
  font-size: clamp(1.25rem, 3vw, 1.5rem);
  font-weight: 400;
  color: var(--color-text-secondary);
  margin-top: var(--spacing-sm);
}

.hero-description {
  font-size: var(--font-size-lg);
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-xl);
  max-width: 700px;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: var(--spacing-md);
  margin-top: var(--spacing-xl);
}

/* ========================================
   Skills Section
   ======================================== */

.skills-section {
  padding: var(--spacing-3xl) 0;
}

.section-heading {
  text-align: center;
  margin-bottom: var(--spacing-xl);
}

.skills-grid {
  display: grid;
  gap: var(--spacing-xl);
  grid-template-columns: 1fr;
}

@media (min-width: 640px) {
  .skills-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1024px) {
  .skills-grid {
    grid-template-columns: repeat(4, 1fr);
  }
}

.skill-card {
  text-align: center;
  padding: var(--spacing-xl);
  background: var(--color-background);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  transition: transform var(--transition-base), box-shadow var(--transition-base);
}

.skill-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
}

.skill-icon {
  color: var(--color-primary);
  margin-bottom: var(--spacing-md);
}

.skill-title {
  font-size: 1.25rem;
  margin-bottom: var(--spacing-sm);
}

.skill-description {
  color: var(--color-text-secondary);
  font-size: var(--font-size-sm);
  margin: 0;
}

/* ========================================
   Projects / Case Studies Section
   ======================================== */

.case-studies-section,
.projects-section {
  padding: var(--spacing-3xl) 0;
  background: var(--color-background-alt);
}

.section-header {
  text-align: center;
  max-width: 800px;
  margin: 0 auto var(--spacing-2xl);
}

.section-intro {
  font-size: var(--font-size-lg);
  color: var(--color-text-secondary);
  margin: 0;
}

.case-studies-grid,
.projects-grid {
  display: grid;
  gap: var(--spacing-xl);
  grid-template-columns: 1fr;
}

@media (min-width: 768px) {
  .case-studies-grid,
  .projects-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

.case-study-card {
  background: var(--color-background);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: transform var(--transition-base), box-shadow var(--transition-base);
}

.case-study-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.case-study-link {
  display: block;
  text-decoration: none;
  color: inherit;
}

.case-study-image {
  width: 100%;
  height: 240px;
  background: var(--color-background-alt);
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
}

.case-study-image img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.image-placeholder {
  color: var(--color-border);
}

.case-study-content {
  padding: var(--spacing-xl);
}

.case-study-title {
  font-size: 1.5rem;
  margin-bottom: var(--spacing-sm);
  color: var(--color-text);
}

.case-study-meta {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  margin-bottom: var(--spacing-md);
}

.meta-item {
  display: inline;
}

.meta-separator {
  margin: 0 var(--spacing-xs);
}

.case-study-summary {
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-md);
}

.case-study-tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-xs);
  margin-bottom: var(--spacing-md);
}

.case-study-cta {
  color: var(--color-primary);
  font-weight: 600;
}

/* ========================================
   CTA Section
   ======================================== */

.cta-section {
  padding: var(--spacing-3xl) 0;
  background: linear-gradient(135deg, #1165C4 0%, #0D50A0 100%);
  text-align: center;
  position: relative;
  overflow: hidden;
}

.cta-section::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: url('data:image/svg+xml,<svg width="100" height="100" xmlns="http://www.w3.org/2000/svg"><circle cx="50" cy="50" r="2" fill="white" opacity="0.1"/></svg>');
  opacity: 0.3;
}

.cta-heading, .cta-text {
  color: white;
  position: relative;
  z-index: 1;
}

.cta-content {
  max-width: 700px;
  margin: 0 auto;
}

.cta-heading {
  font-size: clamp(1.75rem, 4vw, 2.5rem);
  margin-bottom: var(--spacing-md);
}

.cta-text {
  font-size: var(--font-size-lg);
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-xl);
}

.cta-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-md);
  justify-content: center;
}

/* ========================================
   Case Study Detail Page
   ======================================== */

.case-study-detail {
  padding: var(--spacing-2xl) 0;
}

/* Breadcrumb */
.breadcrumb {
  margin-bottom: var(--spacing-xl);
}

.breadcrumb-list {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-sm);
  list-style: none;
  margin: 0;
  font-size: var(--font-size-sm);
}

.breadcrumb-item {
  display: flex;
  align-items: center;
}

.breadcrumb-item:not(:last-child)::after {
  content: '/';
  margin-left: var(--spacing-sm);
  color: var(--color-text-muted);
}

.breadcrumb-item[aria-current="page"] {
  color: var(--color-text-secondary);
}

/* Case Study Header */
.case-study-header {
  margin-bottom: var(--spacing-2xl);
}

.case-study-title {
  margin-bottom: var(--spacing-lg);
}

.case-study-meta-grid {
  display: grid;
  gap: var(--spacing-md);
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  margin-bottom: var(--spacing-lg);
  padding: var(--spacing-lg);
  background: var(--color-background-alt);
  border-radius: var(--radius-md);
}

.meta-group {
  display: flex;
  flex-direction: column;
}

.meta-label {
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--color-text-muted);
  margin-bottom: var(--spacing-xs);
}

.meta-value {
  font-weight: 500;
  color: var(--color-text);
}

.case-study-summary {
  font-size: var(--font-size-lg);
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-md);
}

.case-study-tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-xs);
}

/* Case Study Content - Prose */
.prose {
  max-width: 800px;
  line-height: 1.7;
}

.prose h2 {
  margin-top: var(--spacing-2xl);
  margin-bottom: var(--spacing-md);
}

.prose h3 {
  margin-top: var(--spacing-xl);
  margin-bottom: var(--spacing-md);
}

.prose ul,
.prose ol {
  margin-bottom: var(--spacing-lg);
}

.prose li {
  margin-bottom: var(--spacing-sm);
}

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

.prose code {
  background: var(--color-background-alt);
  padding: 0.2em 0.4em;
  border-radius: var(--radius-sm);
  font-size: 0.9em;
}

.prose pre {
  background: var(--color-background-alt);
  padding: var(--spacing-lg);
  border-radius: var(--radius-md);
  overflow-x: auto;
  margin-bottom: var(--spacing-lg);
}

.prose pre code {
  background: none;
  padding: 0;
}

/* Case Study Footer */
.case-study-footer {
  margin-top: var(--spacing-3xl);
  padding-top: var(--spacing-2xl);
  border-top: 1px solid var(--color-border);
}

.case-study-nav {
  display: grid;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-2xl);
}

@media (min-width: 768px) {
  .case-study-nav {
    grid-template-columns: 1fr auto 1fr;
  }
}

.nav-link {
  display: block;
  padding: var(--spacing-lg);
  background: var(--color-background-alt);
  border-radius: var(--radius-md);
  text-decoration: none;
  transition: background-color var(--transition-base);
}

.nav-link:hover {
  background: var(--color-border);
}

.nav-label {
  display: block;
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--color-primary);
  margin-bottom: var(--spacing-xs);
}

.nav-title {
  display: block;
  color: var(--color-text);
}

.nav-all {
  display: flex;
  align-items: center;
  justify-content: center;
}

.case-study-cta {
  text-align: center;
  padding: var(--spacing-2xl);
  background: var(--color-primary-light);
  border-radius: var(--radius-lg);
}

/* ========================================
   About Page
   ======================================== */

.about-page {
  padding: var(--spacing-2xl) 0;
}

.about-content {
  max-width: 800px;
  margin: 0 auto;
}

.about-intro {
  font-size: var(--font-size-lg);
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-xl);
}