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

:root {
  --color-bg: #ffffff;
  --color-bg-alt: #f7f8fa;
  --color-text: #1a1a1a;
  --color-text-secondary: #555555;
  --color-accent: #2563eb;
  --color-accent-hover: #1d4ed8;
  --color-border: #e5e7eb;
  --color-card-bg: #ffffff;
  --color-nav-bg: rgba(255, 255, 255, 0.95);
  --font-main: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --max-width: 960px;
  --section-padding: 5rem 0;
  --radius: 8px;
}

[data-theme="dark"] {
  --color-bg: #0f0f0f;
  --color-bg-alt: #1a1a1a;
  --color-text: #e5e5e5;
  --color-text-secondary: #a0a0a0;
  --color-accent: #60a5fa;
  --color-accent-hover: #93bbfd;
  --color-border: #2a2a2a;
  --color-card-bg: #161616;
  --color-nav-bg: rgba(15, 15, 15, 0.95);
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
  overflow-x: hidden;
}

body {
  font-family: var(--font-main);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
  overflow-wrap: break-word;
  transition: background-color 0.4s ease, color 0.4s ease;
}

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.5rem;
}

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

ul {
  list-style: none;
}

/* ===========================
   Navigation
   =========================== */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: var(--color-nav-bg);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid transparent;
  transition: border-color 0.3s ease, box-shadow 0.3s ease, background-color 0.4s ease;
}

.nav.scrolled {
  border-bottom-color: var(--color-border);
  box-shadow: 0 1px 8px rgba(0, 0, 0, 0.04);
}

.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.nav-logo {
  font-weight: 700;
  font-size: 1.25rem;
  letter-spacing: -0.02em;
  color: var(--color-text);
}

.nav-links {
  display: flex;
  gap: 2rem;
}

.nav-links a {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  transition: color 0.2s ease;
}

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

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.nav-toggle span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--color-text);
  border-radius: 2px;
  transition: transform 0.3s ease, opacity 0.3s ease;
}

.nav-toggle.active span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.nav-toggle.active span:nth-child(2) {
  opacity: 0;
}

.nav-toggle.active span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* ===========================
   Hero
   =========================== */
.hero {
  padding: 10rem 0 6rem;
  min-height: 80vh;
  display: flex;
  align-items: center;
}

.hero-grid {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 3rem;
}

.hero-text {
  flex: 1;
}

.hero-photo {
  flex-shrink: 0;
}

.hero-photo img {
  width: 260px;
  height: 260px;
  max-width: 100%;
  object-fit: cover;
  object-position: top;
  border-radius: 50%;
  border: 4px solid var(--color-border);
  background: var(--color-bg-alt);
  transition: border-color 0.4s ease, background-color 0.4s ease;
}

.hero-greeting {
  font-size: 1rem;
  color: var(--color-text-secondary);
  margin-bottom: 0.5rem;
  font-weight: 500;
}

.hero-name {
  font-size: 3.25rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.1;
  margin-bottom: 0.75rem;
}

.hero-title {
  font-size: 1.125rem;
  color: var(--color-text-secondary);
  margin-bottom: 1rem;
  font-weight: 400;
}

.hero-tagline {
  font-size: 1.15rem;
  color: var(--color-text);
  margin-bottom: 2rem;
  max-width: 480px;
  line-height: 1.6;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
}

/* Buttons */
.btn {
  display: inline-block;
  padding: 0.7rem 1.6rem;
  font-size: 0.875rem;
  font-weight: 500;
  font-family: var(--font-main);
  border-radius: var(--radius);
  transition: all 0.2s ease;
  cursor: pointer;
  border: none;
}

.btn-primary {
  background: var(--color-text);
  color: var(--color-bg);
}

.btn-primary:hover {
  opacity: 0.85;
}

.btn-outline {
  background: transparent;
  border: 1.5px solid var(--color-border);
  color: var(--color-text);
  transition: all 0.2s ease, border-color 0.4s ease, color 0.4s ease;
}

.btn-outline:hover {
  border-color: var(--color-text);
}

/* ===========================
   Sections (shared)
   =========================== */
.section {
  padding: var(--section-padding);
}

.section-alt {
  background: var(--color-bg-alt);
  transition: background-color 0.4s ease;
}

.section-title {
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 2.5rem;
}

/* ===========================
   About
   =========================== */
.about-content p {
  max-width: 640px;
  color: var(--color-text-secondary);
  margin-bottom: 1rem;
  font-size: 1rem;
}

.about-details {
  display: flex;
  flex-wrap: wrap;
  gap: 2rem;
  margin-top: 2rem;
  padding-top: 2rem;
  border-top: 1px solid var(--color-border);
}

.about-detail {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.about-label {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-text-secondary);
}

.about-detail span:last-child {
  font-size: 0.9rem;
  color: var(--color-text);
}

/* ===========================
   Skills
   =========================== */
.skills-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 2rem;
}

.skill-category h3 {
  font-size: 0.8rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-accent);
  margin-bottom: 1rem;
}

.skill-category ul {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.skill-category li {
  font-size: 0.925rem;
  color: var(--color-text-secondary);
}

/* ===========================
   Projects
   =========================== */
.projects-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.5rem;
}

.project-card {
  background: var(--color-card-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1.75rem;
  transition: border-color 0.2s ease, box-shadow 0.2s ease, background-color 0.4s ease;
}

.project-card:hover {
  border-color: var(--color-accent);
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.04);
}

.project-header {
  display: flex;
  align-items: flex-start;
  gap: 0.75rem;
  margin-bottom: 1rem;
}

.project-icon {
  width: 22px;
  height: 22px;
  flex-shrink: 0;
  color: var(--color-accent);
  margin-top: 2px;
}

.project-header h3 {
  font-size: 1.05rem;
  font-weight: 600;
  line-height: 1.3;
}

.project-card > p {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  line-height: 1.6;
  margin-bottom: 1rem;
}

.project-tech {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-bottom: 1rem;
}

.project-tech span {
  font-size: 0.75rem;
  font-weight: 500;
  padding: 0.25rem 0.65rem;
  background: var(--color-bg-alt);
  border-radius: 4px;
  color: var(--color-text-secondary);
}

.project-impact {
  font-size: 0.8rem;
  font-style: italic;
  color: var(--color-text-secondary);
  opacity: 0.85;
  margin-bottom: 0.75rem;
}

.project-link {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  font-size: 0.825rem;
  font-weight: 500;
  color: var(--color-accent);
  transition: opacity 0.2s ease;
}

.project-link:hover {
  opacity: 0.75;
}

/* ===========================
   Experience
   =========================== */
.experience-block {
  max-width: 640px;
}

.experience-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 1rem;
  margin-bottom: 1.25rem;
  flex-wrap: wrap;
}

.experience-header h3 {
  font-size: 1.1rem;
  font-weight: 600;
}

.experience-company {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  margin-top: 0.2rem;
}

.experience-date {
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  white-space: nowrap;
  padding-top: 0.2rem;
}

.experience-list {
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}

.experience-list li {
  font-size: 0.925rem;
  color: var(--color-text-secondary);
  padding-left: 1.1rem;
  position: relative;
}

.experience-list li::before {
  content: '';
  position: absolute;
  left: 0;
  top: 0.55rem;
  width: 5px;
  height: 5px;
  background: var(--color-accent);
  border-radius: 50%;
}

/* ===========================
   Certifications & Achievements
   =========================== */
.achievements-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.25rem;
}

.achievement-card {
  display: flex;
  align-items: flex-start;
  gap: 1rem;
  padding: 1.25rem 1.5rem;
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  transition: border-color 0.2s ease, background-color 0.4s ease;
}

.achievement-card:hover {
  border-color: var(--color-accent);
}

.achievement-icon {
  flex-shrink: 0;
  width: 20px;
  height: 20px;
  color: var(--color-accent);
  margin-top: 2px;
}

.achievement-icon svg {
  width: 20px;
  height: 20px;
}

.achievement-card h3 {
  font-size: 0.95rem;
  font-weight: 600;
  margin-bottom: 0.25rem;
}

.achievement-card p {
  font-size: 0.85rem;
  color: var(--color-text-secondary);
  line-height: 1.5;
}

.cert-link {
  display: inline-flex;
  align-items: center;
  gap: 0.25rem;
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--color-accent);
  margin-top: 0.5rem;
  transition: opacity 0.2s ease;
}

.cert-link:hover {
  opacity: 0.75;
}

/* ===========================
   Learning
   =========================== */
.learning-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1rem;
}

.learning-item {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 1rem 1.25rem;
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  font-size: 0.925rem;
  color: var(--color-text-secondary);
  transition: background-color 0.4s ease, color 0.4s ease, border-color 0.4s ease;
}

.learning-icon {
  font-size: 1.25rem;
  flex-shrink: 0;
}

/* ===========================
   Contact
   =========================== */
.contact-text {
  font-size: 1rem;
  color: var(--color-text-secondary);
  margin-bottom: 2rem;
  max-width: 480px;
}

.contact-links {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.contact-link {
  display: inline-flex;
  align-items: center;
  gap: 0.75rem;
  font-size: 0.925rem;
  color: var(--color-text-secondary);
  transition: color 0.2s ease;
  width: fit-content;
}

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

.contact-link svg {
  width: 20px;
  height: 20px;
  flex-shrink: 0;
}

/* ===========================
   Footer
   =========================== */
.footer {
  padding: 2rem 0;
  text-align: center;
  border-top: 1px solid var(--color-border);
  transition: border-color 0.4s ease;
}

.footer p {
  font-size: 0.8rem;
  color: var(--color-text-secondary);
}

/* ===========================
   Theme Toggle
   =========================== */
.theme-toggle {
  background: none;
  border: 1.5px solid var(--color-border);
  border-radius: 50%;
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  color: var(--color-text);
  transition: border-color 0.2s ease, color 0.2s ease;
  margin-right: 0.75rem;
}

.theme-toggle:hover {
  border-color: var(--color-text);
}

.theme-toggle svg {
  width: 18px;
  height: 18px;
}

.icon-moon {
  display: none;
}

[data-theme="dark"] .icon-sun {
  display: none;
}

[data-theme="dark"] .icon-moon {
  display: block;
}

/* ===========================
   External link indicator
   =========================== */
.external-indicator {
  font-size: 0.75em;
  margin-left: 0.15rem;
}

/* ===========================
   Scroll Animations
   =========================== */
.fade-in {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ===========================
   Back to Top
   =========================== */
.back-to-top {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  z-index: 90;
  width: 42px;
  height: 42px;
  border-radius: 50%;
  border: 1.5px solid var(--color-border);
  background: var(--color-card-bg);
  color: var(--color-text);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  pointer-events: none;
  transform: translateY(10px);
  transition: opacity 0.3s ease, transform 0.3s ease, background-color 0.4s ease, border-color 0.4s ease;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
}

.back-to-top.show {
  opacity: 1;
  pointer-events: all;
  transform: translateY(0);
}

.back-to-top:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.back-to-top svg {
  width: 20px;
  height: 20px;
}

/* ===========================
   Responsive
   =========================== */

/* Large screens */
@media (min-width: 1200px) {
  :root {
    --max-width: 1080px;
  }

  .hero-name {
    font-size: 3.5rem;
  }

  .hero-photo img {
    width: 300px;
    height: 300px;
  }
}

@media (min-width: 1600px) {
  :root {
    --max-width: 1200px;
  }
}

/* Tablet */
@media (max-width: 768px) {
  .nav-links {
    position: fixed;
    top: 64px;
    left: 0;
    right: 0;
    flex-direction: column;
    background: rgba(255, 255, 255, 0.98);
    backdrop-filter: blur(8px);
    padding: 1.5rem 2rem;
    gap: 1.25rem;
    border-bottom: 1px solid var(--color-border);
    transform: translateY(-120%);
    transition: transform 0.3s ease;
    pointer-events: none;
  }

  [data-theme="dark"] .nav-links {
    background: rgba(15, 15, 15, 0.98);
  }

  .nav-links.open {
    transform: translateY(0);
    pointer-events: all;
  }

  .nav-toggle {
    display: flex;
  }

  .hero {
    padding: 8rem 0 4rem;
    min-height: auto;
  }

  .hero-grid {
    flex-direction: column-reverse;
    text-align: center;
    gap: 2rem;
  }

  .hero-photo img {
    width: 180px;
    height: 180px;
  }

  .hero-tagline {
    margin-inline: auto;
  }

  .hero-actions {
    justify-content: center;
  }

  .nav-links a {
    padding: 0.5rem 0;
    display: block;
    min-height: 44px;
    line-height: 44px;
  }

  .hero-name {
    font-size: 2.25rem;
  }

  .hero-title {
    font-size: 1rem;
  }

  .skills-grid {
    grid-template-columns: 1fr;
    gap: 2rem;
  }

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

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

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

  .experience-header {
    flex-direction: column;
    gap: 0.25rem;
  }

  .about-details {
    flex-direction: column;
    gap: 1.25rem;
  }
}

@media (max-width: 480px) {
  :root {
    --section-padding: 3.5rem 0;
  }

  .hero-name {
    font-size: 2rem;
  }

  .section-title {
    font-size: 1.5rem;
  }

  .hero-actions {
    flex-direction: column;
    gap: 0.75rem;
  }

  .btn {
    text-align: center;
    min-height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
  }

  .project-card {
    padding: 1.25rem;
  }

  .achievement-card {
    padding: 1rem 1.15rem;
  }

  .contact-link {
    min-height: 44px;
  }
}

/* ===========================
   Focus & Skip-to-content (A11y)
   =========================== */
a:focus-visible,
button:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

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