/* ============================================================
   CSS VARIABLES
   ============================================================ */
:root {
  /* Colors */
  --color-white:      #ffffff;
  --color-black:      #1a1a1a;
  --color-gray-50:    #f9fafb;
  --color-gray-100:   #f3f4f6;
  --color-gray-200:   #e5e7eb;
  --color-gray-300:   #d1d5db;
  --color-gray-400:   #9ca3af;
  --color-gray-500:   #6b7280;
  --color-gray-600:   #4b5563;
  --color-gray-700:   #374151;
  --color-gray-800:   #1f2937;
  --color-blue-500:   #2563eb;
  --color-blue-600:   #1d4ed8;
  --color-blue-700:   #1e40af;
  --color-blue-50:    #eff6ff;

  /* Typography */
  --font-sans:        system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono:        "SF Mono", "Fira Code", "Fira Mono", "Roboto Mono", monospace;

  --text-xs:          0.75rem;   /* 12px */
  --text-sm:          0.875rem;  /* 14px */
  --text-base:        1rem;      /* 16px */
  --text-lg:          1.125rem;  /* 18px */
  --text-xl:          1.25rem;   /* 20px */
  --text-2xl:         1.5rem;    /* 24px */
  --text-3xl:         1.875rem;  /* 30px */
  --text-4xl:         2.25rem;   /* 36px */

  --leading-tight:    1.25;
  --leading-normal:   1.6;
  --leading-relaxed:  1.75;

  /* Spacing */
  --space-1:          0.25rem;   /* 4px */
  --space-2:          0.5rem;    /* 8px */
  --space-3:          0.75rem;   /* 12px */
  --space-4:          1rem;      /* 16px */
  --space-5:          1.25rem;   /* 20px */
  --space-6:          1.5rem;    /* 24px */
  --space-8:          2rem;      /* 32px */
  --space-10:         2.5rem;    /* 40px */
  --space-12:         3rem;      /* 48px */
  --space-16:         4rem;      /* 64px */
  --space-20:         5rem;      /* 80px */

  /* Borders & Radius */
  --radius-sm:        6px;
  --radius-md:        10px;
  --radius-lg:        14px;
  --radius-full:      9999px;

  /* Shadows */
  --shadow-sm:        0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md:        0 4px 6px rgba(0, 0, 0, 0.04), 0 2px 4px rgba(0, 0, 0, 0.04);
  --shadow-lg:        0 10px 15px rgba(0, 0, 0, 0.05), 0 4px 6px rgba(0, 0, 0, 0.03);

  /* Layout */
  --max-width:        1024px;
  --header-height:    64px;

  /* Transitions */
  --transition-fast:  150ms ease;
  --transition-base:  250ms ease;

  /* Focus ring */
  --focus-ring:       0 0 0 3px rgba(37, 99, 235, 0.35);
}


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

html {
  scroll-behavior: smooth;
  scroll-padding-top: var(--header-height);
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  font-size: var(--text-base);
  line-height: var(--leading-normal);
  color: var(--color-black);
  background-color: var(--color-white);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

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

ul {
  list-style: none;
}

button {
  font: inherit;
  cursor: pointer;
  background: none;
  border: none;
  color: inherit;
}

/* Focus styles for accessibility */
:focus-visible {
  outline: none;
  box-shadow: var(--focus-ring);
  border-radius: var(--radius-sm);
}

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


/* ============================================================
   UTILITY CLASSES
   ============================================================ */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-6);
}

.section {
  padding: var(--space-16) 0;
}

.section-title {
  font-size: var(--text-2xl);
  font-weight: 700;
  color: var(--color-black);
  text-align: center;
  margin-bottom: var(--space-10);
  position: relative;
}

/* Decorative underline for section titles */
.section-title::after {
  content: "";
  display: block;
  width: 48px;
  height: 3px;
  background-color: var(--color-blue-500);
  margin: var(--space-3) auto 0;
  border-radius: var(--radius-full);
}

.card {
  background: var(--color-white);
  border: 1px solid var(--color-gray-200);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  transition: box-shadow var(--transition-base), transform var(--transition-base);
}

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


/* ============================================================
   BUTTONS
   ============================================================ */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  font-size: var(--text-sm);
  font-weight: 600;
  padding: var(--space-3) var(--space-6);
  border-radius: var(--radius-md);
  transition: background-color var(--transition-fast),
              color var(--transition-fast),
              border-color var(--transition-fast),
              box-shadow var(--transition-fast);
  cursor: pointer;
  white-space: nowrap;
}

.btn-primary {
  background-color: var(--color-blue-500);
  color: var(--color-white);
}

.btn-primary:hover {
  background-color: var(--color-blue-600);
}

.btn-primary:active {
  background-color: var(--color-blue-700);
}

.btn-outline {
  background-color: transparent;
  color: var(--color-blue-500);
  border: 1.5px solid var(--color-blue-500);
}

.btn-outline:hover {
  background-color: var(--color-blue-50);
}

.btn-outline:active {
  background-color: var(--color-blue-500);
  color: var(--color-white);
}

.btn-small {
  font-size: var(--text-xs);
  padding: var(--space-2) var(--space-4);
}


/* ============================================================
   HEADER & NAVIGATION
   ============================================================ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--color-gray-200);
  height: var(--header-height);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.logo {
  font-size: var(--text-lg);
  font-weight: 700;
  color: var(--color-black);
  letter-spacing: -0.02em;
  transition: color var(--transition-fast);
}

.logo:hover {
  color: var(--color-blue-500);
}

/* Navigation */
.site-nav {
  position: relative;
}

.nav-list {
  display: none;
  position: absolute;
  top: 100%;
  right: 0;
  background: var(--color-white);
  border: 1px solid var(--color-gray-200);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-lg);
  padding: var(--space-2) 0;
  min-width: 180px;
  margin-top: var(--space-2);
}

.nav-list.is-open {
  display: block;
}

.nav-link {
  display: block;
  padding: var(--space-2) var(--space-4);
  font-size: var(--text-sm);
  color: var(--color-gray-700);
  transition: color var(--transition-fast), background-color var(--transition-fast);
}

.nav-link:hover {
  color: var(--color-blue-500);
  background-color: var(--color-gray-50);
}

/* Hamburger toggle */
.nav-toggle {
  display: flex;
  flex-direction: column;
  gap: 5px;
  padding: var(--space-2);
  border-radius: var(--radius-sm);
}

.nav-toggle-bar {
  display: block;
  width: 22px;
  height: 2px;
  background-color: var(--color-gray-700);
  border-radius: 2px;
  transition: transform var(--transition-base), opacity var(--transition-base);
}

/* Hamburger open state */
.nav-toggle[aria-expanded="true"] .nav-toggle-bar:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

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

.nav-toggle[aria-expanded="true"] .nav-toggle-bar:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}


/* ============================================================
   HERO SECTION
   ============================================================ */
.hero-section {
  padding: var(--space-16) 0 var(--space-12);
  background-color: var(--color-gray-50);
}

.hero-inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  gap: var(--space-8);
}

.hero-image-wrapper {
  flex-shrink: 0;
}

.hero-image {
  width: 160px;
  height: 160px;
  border-radius: var(--radius-full);
  object-fit: cover;
  border: 3px solid var(--color-white);
  box-shadow: var(--shadow-md);
  background-color: var(--color-gray-200);
}

.hero-text {
  max-width: 580px;
}

.hero-name {
  font-size: var(--text-3xl);
  font-weight: 800;
  color: var(--color-black);
  letter-spacing: -0.03em;
  margin-bottom: var(--space-2);
}

.hero-tagline {
  font-size: var(--text-lg);
  color: var(--color-blue-500);
  font-weight: 600;
  margin-bottom: var(--space-4);
}

.hero-intro {
  font-size: var(--text-base);
  color: var(--color-gray-600);
  line-height: var(--leading-relaxed);
  margin-bottom: var(--space-6);
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  justify-content: center;
}


/* ============================================================
   ABOUT SECTION
   ============================================================ */
.about-section {
  background-color: var(--color-white);
}

.about-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-6);
}

.about-card .card-title {
  font-size: var(--text-lg);
  font-weight: 700;
  margin-bottom: var(--space-3);
  color: var(--color-black);
}

.about-card p {
  font-size: var(--text-sm);
  color: var(--color-gray-600);
  line-height: var(--leading-relaxed);
}


/* ============================================================
   SKILLS SECTION
   ============================================================ */
.skills-section {
  background-color: var(--color-gray-50);
}

.skills-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-4);
}

.skill-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  gap: var(--space-2);
  padding: var(--space-5);
}

.skill-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 56px;
  height: 56px;
  border-radius: var(--radius-md);
  background-color: var(--color-blue-50);
  margin-bottom: var(--space-1);
}

.skill-name {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-black);
}

.skill-level {
  font-size: var(--text-xs);
  color: var(--color-gray-500);
}


/* ============================================================
   PROJECTS SECTION
   ============================================================ */
.projects-section {
  background-color: var(--color-white);
}

.projects-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-8);
}

.project-card {
  overflow: hidden;
  padding: 0;
}

.project-image-wrapper {
  overflow: hidden;
  background-color: var(--color-gray-100);
}

.project-image {
  width: 100%;
  aspect-ratio: 16 / 9;
  object-fit: cover;
  transition: transform var(--transition-base);
}

.project-card:hover .project-image {
  transform: scale(1.03);
}

.project-body {
  padding: var(--space-6);
}

.project-title {
  font-size: var(--text-lg);
  font-weight: 700;
  color: var(--color-black);
  margin-bottom: var(--space-2);
}

.project-description {
  font-size: var(--text-sm);
  color: var(--color-gray-600);
  line-height: var(--leading-relaxed);
  margin-bottom: var(--space-4);
}

.project-tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin-bottom: var(--space-4);
}

.tag {
  font-size: var(--text-xs);
  font-weight: 500;
  padding: var(--space-1) var(--space-3);
  background-color: var(--color-blue-50);
  color: var(--color-blue-500);
  border-radius: var(--radius-full);
}


/* ============================================================
   EXPERIENCE & EDUCATION SECTIONS
   ============================================================ */
.experience-section {
  background-color: var(--color-gray-50);
}

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

.experience-timeline,
.education-timeline {
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
  max-width: 720px;
  margin: 0 auto;
}

.experience-card,
.education-card {
  position: relative;
}

/* Timeline connector line */
.experience-timeline::before,
.education-timeline::before {
  content: "";
  position: absolute;
  left: 24px;
  top: 0;
  bottom: 0;
  width: 2px;
  background-color: var(--color-gray-200);
}

.experience-card::before,
.education-card::before {
  content: "";
  position: absolute;
  left: calc(24px - 5px);
  top: var(--space-6);
  width: 12px;
  height: 12px;
  background-color: var(--color-blue-500);
  border: 2px solid var(--color-white);
  border-radius: var(--radius-full);
  z-index: 1;
}

.experience-header,
.education-header {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: var(--space-3);
  margin-bottom: var(--space-3);
}

.experience-title,
.education-title {
  font-size: var(--text-lg);
  font-weight: 700;
  color: var(--color-black);
}

.experience-badge,
.education-badge {
  font-size: var(--text-xs);
  font-weight: 600;
  padding: var(--space-1) var(--space-3);
  background-color: var(--color-blue-50);
  color: var(--color-blue-500);
  border-radius: var(--radius-full);
}

.experience-description,
.education-description {
  font-size: var(--text-sm);
  color: var(--color-gray-600);
  line-height: var(--leading-relaxed);
  margin-bottom: var(--space-4);
}

.education-major {
  font-size: var(--text-sm);
  color: var(--color-gray-700);
  margin-bottom: var(--space-3);
}

.experience-list,
.education-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.experience-list li,
.education-list li {
  font-size: var(--text-sm);
  color: var(--color-gray-600);
  padding-left: var(--space-5);
  position: relative;
}

.experience-list li::before,
.education-list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 10px;
  width: 6px;
  height: 6px;
  background-color: var(--color-blue-500);
  border-radius: var(--radius-full);
}


/* ============================================================
   CONTACT SECTION
   ============================================================ */
.contact-section {
  background-color: var(--color-gray-50);
}

.contact-intro {
  text-align: center;
  font-size: var(--text-sm);
  color: var(--color-gray-600);
  max-width: 520px;
  margin: 0 auto var(--space-10);
  line-height: var(--leading-relaxed);
}

.contact-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-4);
  max-width: 600px;
  margin: 0 auto;
}

.contact-card {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  padding: var(--space-5);
  cursor: pointer;
  transition: box-shadow var(--transition-base),
              transform var(--transition-base),
              border-color var(--transition-base);
}

.contact-card:hover {
  border-color: var(--color-blue-300);
}

.contact-icon {
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 48px;
  height: 48px;
  border-radius: var(--radius-md);
  background-color: var(--color-blue-50);
  color: var(--color-blue-500);
}

.contact-info {
  display: flex;
  flex-direction: column;
  gap: 2px;
  min-width: 0;
}

.contact-label {
  font-size: var(--text-xs);
  font-weight: 600;
  color: var(--color-gray-500);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.contact-value {
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-black);
  word-break: break-all;
}


/* ============================================================
   FOOTER
   ============================================================ */
.site-footer {
  background-color: var(--color-white);
  border-top: 1px solid var(--color-gray-200);
  padding: var(--space-8) 0;
}

.footer-inner {
  text-align: center;
}

.footer-text {
  font-size: var(--text-sm);
  color: var(--color-gray-600);
  margin-bottom: var(--space-1);
}

.footer-subtext {
  font-size: var(--text-xs);
  color: var(--color-gray-400);
}


/* ============================================================
   RESPONSIVE — TABLET (min-width: 640px)
   ============================================================ */
@media (min-width: 640px) {

  .section-title {
    font-size: var(--text-3xl);
  }

  /* Hero */
  .hero-name {
    font-size: var(--text-4xl);
  }

  .hero-image {
    width: 180px;
    height: 180px;
  }

  /* Skills: 3 columns */
  .skills-grid {
    grid-template-columns: repeat(3, 1fr);
  }

  /* Contact: 2 columns */
  .contact-grid {
    grid-template-columns: repeat(2, 1fr);
    max-width: 640px;
  }

  /* About: 3 columns */
  .about-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}


/* ============================================================
   RESPONSIVE — DESKTOP (min-width: 768px)
   ============================================================ */
@media (min-width: 768px) {

  /* Show nav as horizontal list */
  .nav-toggle {
    display: none;
  }

  .nav-list {
    position: static;
    display: flex;
    flex-direction: row;
    gap: var(--space-1);
    background: transparent;
    border: none;
    box-shadow: none;
    padding: 0;
    margin: 0;
    min-width: 0;
  }

  .nav-link {
    padding: var(--space-2) var(--space-3);
    border-radius: var(--radius-sm);
  }

  /* Hero: side-by-side layout */
  .hero-inner {
    flex-direction: row;
    text-align: left;
    gap: var(--space-12);
    justify-content: center;
  }

  .hero-actions {
    justify-content: flex-start;
  }

  /* Projects: 2-column alternative layout */
  .projects-grid {
    grid-template-columns: 1fr 1fr;
    gap: var(--space-6);
  }

  /* First project spans full width for visual variety */
  .project-card:first-child {
    grid-column: 1 / -1;
  }

  .project-card:first-child .project-body {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-6);
    align-items: start;
  }

  .project-card:first-child .project-description {
    margin-bottom: 0;
  }

  .project-card:first-child .project-tags,
  .project-card:first-child .btn {
    grid-column: 2;
  }

  /* Skills: 4 columns */
  .skills-grid {
    grid-template-columns: repeat(4, 1fr);
  }
}


/* ============================================================
   RESPONSIVE — LARGE DESKTOP (min-width: 1024px)
   ============================================================ */
@media (min-width: 1024px) {

  .hero-section {
    padding: var(--space-20) 0 var(--space-16);
  }

  .section {
    padding: var(--space-20) 0;
  }

  .section-title {
    font-size: var(--text-3xl);
    margin-bottom: var(--space-12);
  }

  .hero-image {
    width: 200px;
    height: 200px;
  }

  /* Projects: full 2-column grid */
  .projects-grid {
    grid-template-columns: 1fr 1fr;
  }

  .project-card:first-child {
    grid-column: span 1;
  }

  .project-card:first-child .project-body {
    display: block;
  }

  .project-card:first-child .project-description {
    margin-bottom: var(--space-4);
  }
}


/* ============================================================
   PROJECT TITLE (CLICKABLE)
   ============================================================ */
.project-title[role="button"] {
  cursor: pointer;
  transition: color var(--transition-fast);
  display: inline-block;
}

.project-title[role="button"]:hover {
  color: var(--color-blue-500);
  text-decoration: underline;
  text-underline-offset: 4px;
}


/* ============================================================
   MODAL / POPUP
   ============================================================ */
.modal-overlay {
  position: fixed;
  inset: 0;
  z-index: 200;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-6);
}

.modal-overlay[hidden] {
  display: none;
}

.modal-backdrop {
  position: absolute;
  inset: 0;
  background-color: rgba(0, 0, 0, 0.55);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
}

.modal-container {
  position: relative;
  background: var(--color-white);
  border-radius: var(--radius-lg);
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.15);
  width: 100%;
  max-width: 720px;
  max-height: calc(100vh - var(--space-12));
  overflow-y: auto;
  animation: modal-slide-in var(--transition-base);
}

@keyframes modal-slide-in {
  from {
    opacity: 0;
    transform: translateY(16px) scale(0.97);
  }
  to {
    opacity: 1;
    transform: translateY(0) scale(1);
  }
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-5) var(--space-6);
  border-bottom: 1px solid var(--color-gray-200);
  position: sticky;
  top: 0;
  background: var(--color-white);
  z-index: 1;
  border-radius: var(--radius-lg) var(--radius-lg) 0 0;
}

.modal-title {
  font-size: var(--text-xl);
  font-weight: 700;
  color: var(--color-black);
}

.modal-close {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: var(--radius-md);
  color: var(--color-gray-500);
  transition: background-color var(--transition-fast), color var(--transition-fast);
  flex-shrink: 0;
}

.modal-close:hover {
  background-color: var(--color-gray-100);
  color: var(--color-black);
}

.modal-body {
  padding: var(--space-6);
}

.modal-description {
  font-size: var(--text-sm);
  color: var(--color-gray-600);
  line-height: var(--leading-relaxed);
  margin-bottom: var(--space-6);
}

.modal-docs {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-5);
}

.modal-doc {
  border-radius: var(--radius-md);
  overflow: hidden;
  border: 1px solid var(--color-gray-200);
  background-color: var(--color-gray-100);
}

.modal-doc-image {
  width: 100%;
  height: auto;
  display: block;
}


/* ============================================================
   MODAL RESPONSIVE
   ============================================================ */
@media (min-width: 640px) {
  .modal-docs {
    grid-template-columns: 1fr 1fr;
  }

  .modal-container {
    max-width: 760px;
  }
}

@media (min-width: 768px) {
  .modal-container {
    max-width: 820px;
  }
}


/* ============================================================
   PRINT STYLES
   ============================================================ */
@media print {
  .site-header,
  .site-footer,
  .btn,
  .nav-toggle,
  .modal-overlay {
    display: none;
  }

  .section {
    padding: var(--space-4) 0;
    page-break-inside: avoid;
  }

  body {
    font-size: 12pt;
    line-height: 1.5;
    color: #000;
  }

  .card {
    box-shadow: none;
    border: 1px solid #ccc;
  }
}