/* ===== CSS Custom Properties ===== */
:root {
  --primary: #6366f1;
  --primary-dark: #4f46e5;
  --primary-light: #818cf8;
  --secondary: #06b6d4;
  --secondary-dark: #0891b2;
  --accent: #f59e0b;
  --background: #0f172a;
  --background-light: #1e293b;
  --background-card: #1e293b;
  --surface: #334155;
  --text: #e2e8f0;
  --text-light: #94a3b8;
  --text-muted: #64748b;
  --white: #ffffff;
  --nav-bg: rgba(15, 23, 42, 0.9);
  --shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
  --shadow-glow: 0 0 30px rgba(99, 102, 241, 0.15);
  --gradient-primary: linear-gradient(135deg, #6366f1 0%, #06b6d4 100%);
  --gradient-hero: linear-gradient(135deg, #0f172a 0%, #1e1b4b 50%, #0f172a 100%);
  --border-subtle: 1px solid rgba(99, 102, 241, 0.15);
  --radius: 1rem;
  --radius-sm: 0.5rem;
}

/* ===== Base/Reset Styles ===== */
*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  font-size: 16px;
  color: var(--text);
  background: var(--background);
  line-height: 1.7;
  overflow-x: hidden;
}

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

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

h1, h2, h3, h4 {
  line-height: 1.3;
}

/* ===== Navigation ===== */
nav {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  z-index: 1000;
  background: var(--nav-bg);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: var(--border-subtle);
  padding: 1rem 2rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  transition: all 0.3s ease;
}

.nav-brand .logo {
  font-weight: 800;
  font-size: 1.5rem;
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  letter-spacing: -0.5px;
}

.nav-links {
  display: flex;
  list-style: none;
  gap: 0.5rem;
  margin: 0;
  padding: 0;
}

.nav-links a {
  font-size: 0.9rem;
  font-weight: 500;
  padding: 0.5rem 1rem;
  border-radius: 2rem;
  transition: all 0.3s ease;
  color: var(--text-light);
}

.nav-links a:hover {
  color: var(--white);
  background: rgba(99, 102, 241, 0.15);
}

.nav-links a.active-link {
  color: var(--white);
  background: rgba(99, 102, 241, 0.2);
}

/* Hamburger menu */
.hamburger {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 0.5rem;
  flex-direction: column;
  gap: 5px;
}

.hamburger-line {
  display: block;
  width: 25px;
  height: 3px;
  background: var(--text);
  border-radius: 2px;
  transition: transform 0.3s ease, opacity 0.3s ease;
}

/* ===== Section Styles ===== */
.section-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 5rem 1.5rem;
}

.section-container h2 {
  text-align: center;
  font-size: 2.5rem;
  font-weight: 800;
  margin-bottom: 1rem;
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.section-container h2::after {
  content: '';
  display: block;
  width: 60px;
  height: 4px;
  background: var(--gradient-primary);
  margin: 1rem auto 2.5rem;
  border-radius: 2px;
}

/* ===== Hero Section ===== */
#hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding-top: 80px;
  background: var(--gradient-hero);
  position: relative;
  overflow: hidden;
}

.hero-particles {
  position: absolute;
  inset: 0;
  background-image:
    radial-gradient(2px 2px at 20% 30%, rgba(99, 102, 241, 0.3), transparent),
    radial-gradient(2px 2px at 40% 70%, rgba(6, 182, 212, 0.2), transparent),
    radial-gradient(1px 1px at 60% 20%, rgba(99, 102, 241, 0.2), transparent),
    radial-gradient(1px 1px at 80% 50%, rgba(6, 182, 212, 0.15), transparent),
    radial-gradient(2px 2px at 10% 80%, rgba(245, 158, 11, 0.1), transparent),
    radial-gradient(1px 1px at 90% 10%, rgba(99, 102, 241, 0.2), transparent);
  animation: particleFloat 20s ease-in-out infinite;
}

@keyframes particleFloat {
  0%, 100% { transform: translateY(0) rotate(0deg); }
  50% { transform: translateY(-20px) rotate(1deg); }
}

.hero-content {
  text-align: center;
  color: var(--white);
  padding: 2rem 1.5rem;
  position: relative;
  z-index: 1;
}

.hero-greeting {
  font-size: 1.1rem;
  color: var(--secondary);
  font-weight: 500;
  letter-spacing: 2px;
  text-transform: uppercase;
  margin: 0 0 0.75rem;
}

/* Hero Avatar */
.hero-avatar {
  width: 160px;
  height: 160px;
  border-radius: 50%;
  margin: 0 auto 1.5rem;
  position: relative;
  background: var(--gradient-primary);
  padding: 4px;
  animation: avatarGlow 3s ease-in-out infinite alternate;
}

@keyframes avatarGlow {
  0% { box-shadow: 0 0 20px rgba(99, 102, 241, 0.3), 0 0 40px rgba(99, 102, 241, 0.1); }
  100% { box-shadow: 0 0 30px rgba(6, 182, 212, 0.4), 0 0 60px rgba(6, 182, 212, 0.15); }
}

.hero-avatar img {
  width: 100%;
  height: 100%;
  border-radius: 50%;
  object-fit: cover;
  display: block;
  border: 3px solid var(--background);
}

.avatar-fallback {
  display: none;
  width: 100%;
  height: 100%;
  border-radius: 50%;
  background: var(--background-light);
  border: 3px solid var(--background);
  align-items: center;
  justify-content: center;
  font-size: 3.5rem;
  color: var(--primary-light);
}

.hero-content h1 {
  font-size: 3.5rem;
  font-weight: 800;
  margin: 0 0 0.75rem;
  letter-spacing: -1px;
  background: linear-gradient(135deg, #ffffff 0%, #c7d2fe 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-subtitle {
  font-size: 1.5rem;
  margin: 0 0 1.5rem;
  color: var(--text-light);
  font-family: 'Fira Code', monospace;
}

.cursor {
  animation: blink 1s step-end infinite;
  color: var(--secondary);
  margin-left: 2px;
}

@keyframes blink {
  50% { opacity: 0; }
}

.hero-tagline {
  max-width: 600px;
  margin: 0 auto 2.5rem;
  font-size: 1.1rem;
  color: var(--text-light);
  line-height: 1.7;
}

.hero-buttons {
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
}

.cta-button {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.875rem 2rem;
  background: var(--gradient-primary);
  color: var(--white);
  border-radius: 2rem;
  font-weight: 600;
  font-size: 1rem;
  transition: all 0.3s ease;
  border: 2px solid transparent;
}

.cta-button:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 25px rgba(99, 102, 241, 0.4);
}

.cta-outline {
  background: transparent;
  border: 2px solid var(--primary-light);
  color: var(--primary-light);
}

.cta-outline:hover {
  background: rgba(99, 102, 241, 0.1);
  box-shadow: 0 8px 25px rgba(99, 102, 241, 0.2);
}

.hero-scroll-indicator {
  margin-top: 3rem;
  animation: bounce 2s ease-in-out infinite;
  color: var(--text-muted);
  font-size: 1.25rem;
}

@keyframes bounce {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(10px); }
}

/* ===== About Section ===== */
#about {
  background: var(--background-light);
  position: relative;
}

.about-summary {
  max-width: 800px;
  margin: 0 auto 2rem;
  text-align: center;
  font-size: 1.15rem;
  color: var(--text-light);
  line-height: 1.8;
}

/* Stats Counter Row */
.stats-row {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1.5rem;
  margin-bottom: 3rem;
  max-width: 800px;
  margin-left: auto;
  margin-right: auto;
}

.stat-item {
  text-align: center;
  padding: 1.5rem 1rem;
  background: var(--background);
  border-radius: var(--radius);
  border: var(--border-subtle);
  transition: all 0.3s ease;
}

.stat-item:hover {
  border-color: var(--primary);
  box-shadow: var(--shadow-glow);
  transform: translateY(-4px);
}

.stat-number {
  font-size: 2.5rem;
  font-weight: 800;
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  display: inline;
}

.stat-suffix {
  font-size: 2rem;
  font-weight: 700;
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.stat-label {
  display: block;
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-top: 0.25rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.about-details {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 1.5rem;
  margin-top: 2rem;
}

.about-item {
  background: var(--background);
  padding: 2rem;
  border-radius: var(--radius);
  border: var(--border-subtle);
  transition: all 0.3s ease;
  text-align: center;
}

.about-item:hover {
  border-color: var(--primary);
  box-shadow: var(--shadow-glow);
  transform: translateY(-4px);
}

.about-icon {
  width: 50px;
  height: 50px;
  border-radius: 50%;
  background: var(--gradient-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 1rem;
  font-size: 1.2rem;
  color: var(--white);
}

.about-item strong {
  display: block;
  color: var(--white);
  font-size: 1.1rem;
  margin-bottom: 0.5rem;
}

.about-item p {
  color: var(--text-light);
  margin: 0;
}

.hobbies-list,
.languages-list {
  list-style: none;
  padding: 0;
  margin: 0.5rem 0 0;
  text-align: left;
}

.hobbies-list li,
.languages-list li {
  margin-bottom: 0.35rem;
  color: var(--text-light);
  font-size: 0.95rem;
  padding-left: 1.25rem;
  position: relative;
}

.hobbies-list li::before,
.languages-list li::before {
  content: '▸';
  position: absolute;
  left: 0;
  color: var(--secondary);
}

/* ===== Skills Section ===== */
#skills {
  background: var(--background);
}

.skills-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 3rem;
  align-items: start;
}

.skills-bars h3,
.skills-category h3 {
  color: var(--secondary);
  margin-bottom: 1.25rem;
  font-size: 1rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.skills-bars h3 i,
.skills-category h3 i {
  font-size: 0.9rem;
}

.skill-bar-item {
  margin-bottom: 1.25rem;
}

.skill-bar-header {
  display: flex;
  justify-content: space-between;
  margin-bottom: 0.4rem;
  font-size: 0.9rem;
  color: var(--text);
}

.skill-percent {
  color: var(--primary-light);
  font-family: 'Fira Code', monospace;
  font-size: 0.85rem;
}

.skill-bar {
  height: 8px;
  background: var(--surface);
  border-radius: 4px;
  overflow: hidden;
}

.skill-bar-fill {
  height: 100%;
  width: 0;
  background: var(--gradient-primary);
  border-radius: 4px;
  transition: width 1.5s cubic-bezier(0.4, 0, 0.2, 1);
  position: relative;
}

.skill-bar-fill::after {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: linear-gradient(90deg, transparent, rgba(255,255,255,0.15), transparent);
  animation: shimmer 2s ease-in-out infinite;
}

@keyframes shimmer {
  0% { transform: translateX(-100%); }
  100% { transform: translateX(100%); }
}

.skills-tags-section {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.skills-category {
  margin-bottom: 2.5rem;
}

.skills-category h3 {
  color: var(--secondary);
  margin-bottom: 1rem;
  font-size: 1.15rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
  font-size: 0.95rem;
}

.skills-group {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.skill-tag {
  display: inline-block;
  padding: 0.6rem 1.25rem;
  background: rgba(99, 102, 241, 0.1);
  color: var(--primary-light);
  border: 1px solid rgba(99, 102, 241, 0.2);
  border-radius: 2rem;
  font-size: 0.9rem;
  font-weight: 500;
  transition: all 0.3s ease;
}

.skill-tag:hover {
  background: rgba(99, 102, 241, 0.2);
  border-color: var(--primary);
  transform: translateY(-2px);
  box-shadow: 0 4px 15px rgba(99, 102, 241, 0.2);
}

/* ===== Experience Section ===== */
#experience {
  background: var(--background-light);
}

.experience-subsection {
  margin-bottom: 2.5rem;
}

.experience-subsection h3 {
  color: var(--secondary);
  font-size: 1.1rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
  padding-bottom: 0.75rem;
  margin-bottom: 1.5rem;
  border-bottom: 2px solid rgba(6, 182, 212, 0.2);
}

.experience-entry {
  background: var(--background);
  padding: 1.75rem;
  border-radius: var(--radius);
  border: var(--border-subtle);
  margin-bottom: 1.5rem;
  border-left: 4px solid var(--primary);
  transition: all 0.3s ease;
}

.experience-entry:hover {
  border-left-color: var(--secondary);
  box-shadow: var(--shadow-glow);
  transform: translateX(4px);
}

.experience-entry h4 {
  font-size: 1.2rem;
  margin: 0 0 0.25rem;
  color: var(--white);
}

.experience-company {
  color: var(--primary-light);
  font-weight: 500;
  margin: 0;
}

.experience-date {
  color: var(--secondary);
  font-size: 0.85rem;
  font-weight: 600;
  font-family: 'Fira Code', monospace;
  margin: 0.25rem 0;
}

.experience-description {
  margin-top: 0.75rem;
  color: var(--text-light);
}

/* ===== Projects Section ===== */
#projects {
  background: var(--background);
}

.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 1.5rem;
}

.project-card {
  background: var(--background-light);
  padding: 2rem;
  border-radius: var(--radius);
  border: var(--border-subtle);
  transition: all 0.4s ease;
  position: relative;
  overflow: hidden;
}

.project-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: var(--gradient-primary);
  transform: scaleX(0);
  transition: transform 0.4s ease;
}

.project-card:hover {
  box-shadow: var(--shadow-glow);
  border-color: var(--primary);
}

.project-card:hover::before {
  transform: scaleX(1);
}

.project-card h3 {
  color: var(--white);
  margin: 0 0 0.5rem;
  font-size: 1.15rem;
}

.project-duration {
  color: var(--text-muted);
  font-size: 0.85rem;
  font-family: 'Fira Code', monospace;
  margin: 0;
}

.project-description {
  color: var(--text-light);
  margin: 1rem 0;
  font-size: 0.95rem;
}

.project-technologies {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin: 1rem 0;
}

.tech-tag {
  font-size: 0.75rem;
  padding: 0.3rem 0.75rem;
  background: rgba(6, 182, 212, 0.1);
  color: var(--secondary);
  border: 1px solid rgba(6, 182, 212, 0.2);
  border-radius: 1rem;
  font-family: 'Fira Code', monospace;
}

.project-achievement {
  color: var(--accent);
  font-weight: 600;
  font-size: 0.95rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin: 0;
}

.project-achievement::before {
  content: '✦';
  color: var(--accent);
}

/* ===== Education Section ===== */
#education {
  background: var(--background-light);
}

.education-entries {
  max-width: 800px;
  margin: 0 auto;
}

.education-entry {
  background: var(--background);
  padding: 1.75rem;
  border-radius: var(--radius);
  border: var(--border-subtle);
  margin-bottom: 1.5rem;
  transition: all 0.3s ease;
}

.education-entry:hover {
  border-color: var(--primary);
  box-shadow: var(--shadow-glow);
  transform: translateY(-3px);
}

.education-entry h3 {
  margin: 0 0 0.25rem;
  color: var(--white);
  font-size: 1.15rem;
}

.education-institution {
  color: var(--text-light);
  margin: 0;
}

.education-year {
  color: var(--secondary);
  font-weight: 600;
  font-family: 'Fira Code', monospace;
  font-size: 0.9rem;
  margin: 0.25rem 0;
}

.education-grade {
  color: var(--accent);
  font-weight: 600;
  margin: 0;
}

/* ===== Contact Section ===== */
#contact {
  background: var(--background);
}

.contact-info {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 2rem;
  margin-bottom: 3rem;
}

.contact-item {
  text-align: center;
  background: var(--background-light);
  padding: 2rem;
  border-radius: var(--radius);
  border: var(--border-subtle);
  min-width: 200px;
  transition: all 0.3s ease;
}

.contact-item:hover {
  border-color: var(--primary);
  box-shadow: var(--shadow-glow);
  transform: translateY(-4px);
}

.contact-icon {
  width: 50px;
  height: 50px;
  border-radius: 50%;
  background: var(--gradient-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 1rem;
  font-size: 1.2rem;
  color: var(--white);
}

.contact-item strong {
  display: block;
  color: var(--white);
  margin-bottom: 0.5rem;
}

.contact-item a,
.contact-item p {
  color: var(--text-light);
  font-size: 0.9rem;
  margin: 0;
  transition: color 0.3s ease;
}

.contact-item a:hover {
  color: var(--primary-light);
  text-decoration: none;
}

#contact-form {
  max-width: 600px;
  margin: 0 auto;
  background: var(--background-light);
  padding: 2.5rem;
  border-radius: var(--radius);
  border: var(--border-subtle);
}

.form-group {
  margin-bottom: 1.5rem;
}

.form-group label {
  display: block;
  margin-bottom: 0.5rem;
  font-weight: 600;
  color: var(--text);
  font-size: 0.95rem;
}

.form-group input,
.form-group textarea {
  width: 100%;
  padding: 0.875rem 1rem;
  border: 1px solid var(--surface);
  border-radius: var(--radius-sm);
  font-size: 1rem;
  font-family: inherit;
  background: var(--background);
  color: var(--text);
  transition: all 0.3s ease;
}

.form-group input::placeholder,
.form-group textarea::placeholder {
  color: var(--text-muted);
}

.form-group input:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.15);
}

.form-group textarea {
  min-height: 130px;
  resize: vertical;
}

.error-message {
  color: #f87171;
  font-size: 0.85rem;
  margin-top: 0.25rem;
  min-height: 1.25rem;
}

button[type="submit"] {
  width: 100%;
  padding: 1rem;
  background: var(--gradient-primary);
  color: var(--white);
  border: none;
  border-radius: var(--radius-sm);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.3s ease;
}

button[type="submit"]:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 25px rgba(99, 102, 241, 0.4);
}

.success-message {
  text-align: center;
  color: var(--secondary);
  font-weight: 600;
  padding: 1rem;
  font-size: 1.1rem;
}

/* ===== Footer ===== */
footer {
  background: var(--background-light);
  border-top: var(--border-subtle);
  color: var(--text);
  padding: 3rem 0;
  text-align: center;
}

.footer-content {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 1.5rem;
}

.footer-links {
  display: flex;
  justify-content: center;
  gap: 2rem;
  margin-bottom: 1.5rem;
}

.footer-links a {
  color: var(--text-light);
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.5rem 1rem;
  border-radius: 2rem;
  transition: all 0.3s ease;
  font-size: 0.95rem;
}

.footer-links a:hover {
  color: var(--white);
  background: rgba(99, 102, 241, 0.15);
}

.copyright {
  font-size: 0.85rem;
  color: var(--text-muted);
}

/* ===== Staggered Animations ===== */
.about-item,
.project-card,
.education-entry,
.experience-entry,
.contact-item,
.skill-tag,
.stat-item {
  opacity: 0;
  transform: translateY(20px);
}

section.animate-in .about-item,
section.animate-in .project-card,
section.animate-in .education-entry,
section.animate-in .experience-entry,
section.animate-in .contact-item,
section.animate-in .stat-item {
  animation: staggerFadeIn 0.6s ease forwards;
}

section.animate-in .skill-tag {
  animation: staggerFadeIn 0.4s ease forwards;
}

@keyframes staggerFadeIn {
  to { opacity: 1; transform: translateY(0); }
}

/* Stagger delays */
section.animate-in .about-item:nth-child(1),
section.animate-in .stat-item:nth-child(1) { animation-delay: 0.1s; }
section.animate-in .about-item:nth-child(2),
section.animate-in .stat-item:nth-child(2) { animation-delay: 0.2s; }
section.animate-in .about-item:nth-child(3),
section.animate-in .stat-item:nth-child(3) { animation-delay: 0.3s; }
section.animate-in .about-item:nth-child(4),
section.animate-in .stat-item:nth-child(4) { animation-delay: 0.4s; }

section.animate-in .project-card:nth-child(1) { animation-delay: 0.1s; }
section.animate-in .project-card:nth-child(2) { animation-delay: 0.25s; }
section.animate-in .project-card:nth-child(3) { animation-delay: 0.4s; }

section.animate-in .education-entry:nth-child(1) { animation-delay: 0.1s; }
section.animate-in .education-entry:nth-child(2) { animation-delay: 0.25s; }
section.animate-in .education-entry:nth-child(3) { animation-delay: 0.4s; }

section.animate-in .experience-entry:nth-child(1) { animation-delay: 0.1s; }
section.animate-in .experience-entry:nth-child(2) { animation-delay: 0.25s; }

section.animate-in .contact-item:nth-child(1) { animation-delay: 0.1s; }
section.animate-in .contact-item:nth-child(2) { animation-delay: 0.2s; }
section.animate-in .contact-item:nth-child(3) { animation-delay: 0.3s; }

section.animate-in .skill-tag:nth-child(1) { animation-delay: 0.05s; }
section.animate-in .skill-tag:nth-child(2) { animation-delay: 0.1s; }
section.animate-in .skill-tag:nth-child(3) { animation-delay: 0.15s; }
section.animate-in .skill-tag:nth-child(4) { animation-delay: 0.2s; }

/* ===== Back to Top Button ===== */
.back-to-top {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--gradient-primary);
  color: var(--white);
  border: none;
  cursor: pointer;
  font-size: 1.1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  visibility: hidden;
  transform: translateY(20px);
  transition: all 0.3s ease;
  z-index: 999;
  box-shadow: 0 4px 15px rgba(99, 102, 241, 0.4);
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-to-top:hover {
  transform: translateY(-4px);
  box-shadow: 0 8px 25px rgba(99, 102, 241, 0.5);
}

/* ===== Scroll Animation ===== */
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(30px); }
  to { opacity: 1; transform: translateY(0); }
}

section .section-container {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.8s ease, transform 0.8s ease;
}

section.animate-in .section-container {
  opacity: 1;
  transform: translateY(0);
}

#hero .hero-content {
  opacity: 1;
  transform: none;
}

/* ===== Prefers Reduced Motion ===== */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  section .section-container { opacity: 1; transform: none; transition: none; }
  .cta-button, .project-card, .about-item, .contact-item, .experience-entry, .education-entry { transition: none; }
  .hero-particles { animation: none; }
  .cursor { animation: none; }
  .hero-scroll-indicator { animation: none; }
}

/* ===== Focus Visible ===== */
:focus-visible {
  outline: 3px solid var(--primary);
  outline-offset: 2px;
}

a:focus-visible,
button:focus-visible {
  border-radius: 4px;
}

/* ===== Responsive: Mobile (below 768px) ===== */
@media (max-width: 767px) {
  .hamburger {
    display: flex;
  }

  .nav-links {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    width: 100%;
    flex-direction: column;
    background: var(--nav-bg);
    backdrop-filter: blur(20px);
    padding: 1rem 2rem;
    gap: 0.5rem;
    border-bottom: var(--border-subtle);
  }

  .nav-links.active {
    display: flex;
  }

  nav {
    padding: 0.75rem 1rem;
  }

  .section-container {
    padding: 3rem 1rem;
  }

  .section-container h2 {
    font-size: 1.75rem;
  }

  .section-container h2::after {
    margin: 0.75rem auto 1.5rem;
  }

  /* Hero mobile */
  #hero {
    padding-top: 60px;
    min-height: 100svh;
  }

  .hero-content {
    padding: 1.5rem 1rem;
  }

  .hero-content h1 {
    font-size: 2rem;
    letter-spacing: -0.5px;
  }

  .hero-avatar {
    width: 110px;
    height: 110px;
    margin-bottom: 1rem;
  }

  .avatar-fallback {
    font-size: 2.5rem;
  }

  .hero-greeting {
    font-size: 0.9rem;
    letter-spacing: 1.5px;
  }

  .hero-subtitle {
    font-size: 1.05rem;
    margin-bottom: 1rem;
  }

  .hero-tagline {
    font-size: 0.95rem;
    margin-bottom: 1.5rem;
    padding: 0 0.5rem;
  }

  .hero-buttons {
    flex-direction: column;
    align-items: center;
    gap: 0.75rem;
  }

  .cta-button {
    width: 100%;
    max-width: 280px;
    justify-content: center;
    padding: 0.75rem 1.5rem;
    font-size: 0.95rem;
  }

  .hero-scroll-indicator {
    margin-top: 2rem;
  }

  /* About mobile */
  .about-summary {
    font-size: 1rem;
    padding: 0 0.5rem;
  }

  .stats-row {
    grid-template-columns: repeat(2, 1fr);
    gap: 0.75rem;
    margin-bottom: 2rem;
  }

  .stat-item {
    padding: 1rem 0.75rem;
  }

  .stat-number {
    font-size: 1.75rem;
  }

  .stat-suffix {
    font-size: 1.25rem;
  }

  .stat-label {
    font-size: 0.7rem;
  }

  .about-details {
    grid-template-columns: 1fr;
    gap: 1rem;
  }

  .about-item {
    padding: 1.5rem;
  }

  /* Skills mobile */
  .skills-layout {
    grid-template-columns: 1fr;
    gap: 2rem;
  }

  .skill-tag {
    padding: 0.5rem 1rem;
    font-size: 0.85rem;
  }

  .skill-bar-header {
    font-size: 0.85rem;
  }

  /* Experience mobile */
  .experience-entry {
    padding: 1.25rem;
  }

  .experience-entry h4 {
    font-size: 1.05rem;
  }

  .experience-entry:hover {
    transform: translateX(2px);
  }

  /* Projects mobile */
  .projects-grid {
    grid-template-columns: 1fr;
    gap: 1rem;
  }

  .project-card {
    padding: 1.5rem;
  }

  .project-card h3 {
    font-size: 1.05rem;
  }

  /* Education mobile */
  .education-entry {
    padding: 1.25rem;
  }

  /* Contact mobile */
  .contact-info {
    flex-direction: column;
    align-items: stretch;
    gap: 1rem;
  }

  .contact-item {
    min-width: unset;
    padding: 1.5rem;
  }

  #contact-form {
    padding: 1.25rem;
  }

  .form-group input,
  .form-group textarea {
    padding: 0.75rem;
    font-size: 16px; /* prevents iOS zoom on focus */
  }

  /* Footer mobile */
  .footer-links {
    flex-direction: column;
    align-items: center;
    gap: 0.75rem;
  }

  /* Back to top mobile */
  .back-to-top {
    bottom: 1rem;
    right: 1rem;
    width: 42px;
    height: 42px;
    font-size: 1rem;
  }
}

/* ===== Small phones (below 380px) ===== */
@media (max-width: 379px) {
  .hero-content h1 {
    font-size: 1.65rem;
  }

  .hero-subtitle {
    font-size: 0.95rem;
  }

  .hero-avatar {
    width: 90px;
    height: 90px;
  }

  .stats-row {
    grid-template-columns: 1fr 1fr;
    gap: 0.5rem;
  }

  .stat-number {
    font-size: 1.5rem;
  }

  .section-container h2 {
    font-size: 1.5rem;
  }
}

/* ===== Tablet (768px–1023px) ===== */
@media (min-width: 768px) and (max-width: 1023px) {
  .section-container {
    padding: 4rem 2rem;
  }

  .hero-content h1 {
    font-size: 2.75rem;
  }

  .hero-avatar {
    width: 140px;
    height: 140px;
  }

  .stats-row {
    grid-template-columns: repeat(4, 1fr);
    gap: 1rem;
  }

  .about-details {
    grid-template-columns: repeat(2, 1fr);
  }

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

  .projects-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .contact-info {
    gap: 1.5rem;
  }

  .contact-item {
    min-width: 180px;
    padding: 1.5rem;
  }
}

/* ===== Desktop (≥1024px) ===== */
@media (min-width: 1024px) {
  .hero-content h1 {
    font-size: 4rem;
  }
  .hero-avatar {
    width: 180px;
    height: 180px;
  }
  .section-container {
    padding: 6rem 2rem;
  }
  .about-details {
    grid-template-columns: repeat(4, 1fr);
  }
  .projects-grid {
    grid-template-columns: repeat(3, 1fr);
  }
  .contact-info {
    gap: 2rem;
  }
}

/* ===== Touch device optimizations ===== */
@media (hover: none) {
  .project-card:hover,
  .about-item:hover,
  .contact-item:hover,
  .education-entry:hover,
  .experience-entry:hover,
  .stat-item:hover {
    transform: none;
    box-shadow: none;
  }

  .skill-tag:hover {
    transform: none;
    box-shadow: none;
  }

  .cta-button:hover {
    transform: none;
    box-shadow: none;
  }

  button[type="submit"]:hover {
    transform: none;
    box-shadow: none;
  }
}