/* ==========================================================
   Personal Website — Dark Premium Theme
   Design: dark glassmorphism, gradient accents, smooth animations
   ========================================================== */

/* ===== 1. CSS Variables ===== */
:root {
  --bg-primary: #0a0a0f;
  --bg-secondary: #12121a;
  --bg-card: rgba(26, 26, 46, 0.7);
  --text-primary: #e8e8f0;
  --text-secondary: #8888a0;
  --text-muted: #5a5a72;
  --accent-1: #667eea;
  --accent-2: #764ba2;
  --accent-gradient: linear-gradient(135deg, #667eea, #764ba2);
  --glass-bg: rgba(26, 26, 46, 0.6);
  --glass-border: rgba(255, 255, 255, 0.06);
  --glass-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
  --card-hover-shadow: 0 8px 40px rgba(102, 126, 234, 0.15);
  --glow: 0 0 30px rgba(102, 126, 234, 0.1);
  --radius: 12px;
  --radius-lg: 20px;
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-cn: 'Noto Sans SC', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
}

/* ===== 2. Reset & Base ===== */
*, *::before, *::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-cn);
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.7;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

ul {
  list-style: none;
}

::selection {
  background: rgba(102, 126, 234, 0.3);
  color: #fff;
}

.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 24px;
}

.section {
  padding: 100px 0;
  position: relative;
}

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

/* ===== 3. Floating Gradient Orbs ===== */
.orb {
  position: fixed;
  border-radius: 50%;
  filter: blur(80px);
  opacity: 0.12;
  pointer-events: none;
  z-index: -1;
}

.orb-1 {
  width: 500px;
  height: 500px;
  background: #667eea;
  top: -200px;
  right: -150px;
  animation: float-orb1 25s ease-in-out infinite;
}

.orb-2 {
  width: 400px;
  height: 400px;
  background: #764ba2;
  bottom: -150px;
  left: -150px;
  animation: float-orb2 30s ease-in-out infinite;
}

.orb-3 {
  width: 250px;
  height: 250px;
  background: #4facfe;
  top: 40%;
  left: 60%;
  animation: float-orb3 20s ease-in-out infinite;
}

/* ===== 4. Navbar ===== */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  transition: background var(--transition), border-color var(--transition);
  background: transparent;
  border-bottom: 1px solid transparent;
}

.navbar.scrolled {
  background: rgba(10, 10, 15, 0.8);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom-color: var(--glass-border);
}

.navbar .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 70px;
}

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

.nav-links {
  display: flex;
  gap: 36px;
}

.nav-links a {
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-secondary);
  transition: color var(--transition);
  position: relative;
  padding: 4px 0;
}

.nav-links a::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--accent-gradient);
  transition: width var(--transition);
  border-radius: 1px;
}

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

.nav-links a:hover::after {
  width: 100%;
}

.menu-toggle {
  display: none;
  font-size: 1.5rem;
  background: none;
  border: none;
  cursor: pointer;
  color: var(--text-primary);
  padding: 4px;
}

/* ===== 5. Hero ===== */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  overflow: hidden;
  padding-top: 70px;
  background: var(--bg-primary);
}

/* Grid background pattern */
.hero-grid-bg {
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(102, 126, 234, 0.04) 1px, transparent 1px),
    linear-gradient(90deg, rgba(102, 126, 234, 0.04) 1px, transparent 1px);
  background-size: 60px 60px;
  -webkit-mask-image: radial-gradient(ellipse 60% 45% at center, black, transparent 80%);
  mask-image: radial-gradient(ellipse 60% 45% at center, black, transparent 80%);
}

.hero-content {
  text-align: center;
  max-width: 750px;
  margin: 0 auto;
  position: relative;
  z-index: 1;
}

/* Avatar — CSS gradient circle with initials */
.hero-avatar {
  width: 100px;
  height: 100px;
  border-radius: 50%;
  background: var(--accent-gradient);
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 36px;
  box-shadow: 0 0 40px rgba(102, 126, 234, 0.25);
  position: relative;
}

.hero-avatar::before {
  content: '';
  position: absolute;
  inset: -4px;
  border-radius: 50%;
  background: var(--accent-gradient);
  opacity: 0.4;
  filter: blur(10px);
  z-index: -1;
}

.avatar-initials {
  font-family: var(--font-sans);
  font-size: 2rem;
  font-weight: 700;
  color: #fff;
  letter-spacing: 2px;
}

.hero h1 {
  font-size: 3.5rem;
  font-weight: 800;
  margin-bottom: 16px;
  line-height: 1.2;
  letter-spacing: -1px;
}

.highlight {
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.subtitle {
  font-size: 1.25rem;
  color: var(--text-secondary);
  margin-bottom: 16px;
  min-height: 1.8em;
  font-family: var(--font-sans);
  font-weight: 400;
}

.cursor {
  display: inline-block;
  color: var(--accent-1);
  animation: blink 1s step-end infinite;
  font-weight: 200;
  margin-left: 1px;
}

.description {
  font-size: 1.1rem;
  color: var(--text-muted);
  margin-bottom: 40px;
  max-width: 540px;
  margin-left: auto;
  margin-right: auto;
  line-height: 1.8;
}

.hero-buttons {
  display: flex;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
}

/* ===== 6. Buttons ===== */
.btn {
  padding: 14px 36px;
  border-radius: 50px;
  font-size: 0.95rem;
  font-weight: 600;
  transition: all var(--transition);
  display: inline-block;
  font-family: var(--font-cn);
  cursor: pointer;
  border: none;
}

.btn-primary {
  background: var(--accent-gradient);
  color: #fff;
  box-shadow: 0 4px 20px rgba(102, 126, 234, 0.3);
}

.btn-primary:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 30px rgba(102, 126, 234, 0.45);
}

.btn-outline {
  border: 2px solid rgba(102, 126, 234, 0.4);
  color: var(--accent-1);
  background: transparent;
}

.btn-outline:hover {
  background: rgba(102, 126, 234, 0.1);
  border-color: var(--accent-1);
  transform: translateY(-3px);
}

/* ===== 7. Section Titles ===== */
.section-title {
  font-size: 2.2rem;
  font-weight: 700;
  text-align: center;
  margin-bottom: 56px;
  position: relative;
}

.section-title::after {
  content: '';
  display: block;
  width: 50px;
  height: 3px;
  background: var(--accent-gradient);
  margin: 16px auto 0;
  border-radius: 2px;
}

/* ===== 8. About ===== */
.about-content {
  max-width: 800px;
  margin: 0 auto;
}

.about-text p {
  font-size: 1.1rem;
  color: var(--text-secondary);
  margin-bottom: 20px;
  text-align: center;
  line-height: 1.8;
}

.about-stats {
  display: flex;
  justify-content: center;
  gap: 60px;
  margin-top: 48px;
  padding: 36px 48px;
  background: var(--glass-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-lg);
}

.stat {
  text-align: center;
}

.stat-number {
  display: block;
  font-size: 2.8rem;
  font-weight: 800;
  font-family: var(--font-sans);
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  letter-spacing: -1px;
}

.stat-label {
  font-size: 0.95rem;
  color: var(--text-muted);
  margin-top: 4px;
  font-weight: 500;
}

/* ===== 9. Skills ===== */
.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 24px;
}

.skill-card {
  background: var(--glass-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-lg);
  padding: 36px 28px 28px;
  text-align: center;
  transition: all var(--transition);
  position: relative;
  overflow: hidden;
}

.skill-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 1px;
  background: var(--accent-gradient);
  opacity: 0;
  transition: opacity var(--transition);
}

.skill-card:hover {
  transform: translateY(-8px);
  border-color: rgba(102, 126, 234, 0.2);
  box-shadow: var(--card-hover-shadow);
}

.skill-card:hover::before {
  opacity: 1;
}

.skill-icon {
  font-size: 2.5rem;
  margin-bottom: 16px;
  display: block;
}

.skill-card h3 {
  font-size: 1.25rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.skill-card > p {
  color: var(--text-secondary);
  font-size: 0.9rem;
  margin-bottom: 20px;
  line-height: 1.6;
}

/* Skill progress bar */
.skill-bar-track {
  height: 6px;
  background: rgba(255, 255, 255, 0.06);
  border-radius: 3px;
  overflow: hidden;
  margin-bottom: 8px;
}

.skill-bar-fill {
  height: 100%;
  width: 0;
  background: var(--accent-gradient);
  border-radius: 3px;
  transition: width 1.2s cubic-bezier(0.4, 0, 0.2, 1);
}

.skill-percent {
  font-size: 0.8rem;
  font-family: var(--font-sans);
  color: var(--text-muted);
  font-weight: 500;
}

/* ===== 10. Projects ===== */
.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 28px;
}

.project-card {
  background: var(--glass-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: all var(--transition);
}

.project-card:hover {
  transform: translateY(-8px);
  border-color: rgba(102, 126, 234, 0.2);
  box-shadow: var(--card-hover-shadow);
}

.project-image {
  height: 200px;
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  overflow: hidden;
  background-size: 200% 200%;
  animation: gradient-shift 6s ease infinite;
}

.project-image::after {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(to bottom, transparent 50%, rgba(10, 10, 15, 0.85));
}

.project-image-1 {
  background-image: linear-gradient(135deg, #667eea, #764ba2, #667eea);
}

.project-image-2 {
  background-image: linear-gradient(135deg, #f093fb, #f5576c, #f093fb);
}

.project-image-3 {
  background-image: linear-gradient(135deg, #4facfe, #00f2fe, #4facfe);
}

.project-placeholder {
  color: #fff;
  font-size: 1.6rem;
  font-weight: 700;
  text-shadow: 0 2px 16px rgba(0, 0, 0, 0.4);
  z-index: 1;
  letter-spacing: 3px;
}

.project-info {
  padding: 28px;
}

.project-info h3 {
  font-size: 1.2rem;
  font-weight: 700;
  margin-bottom: 10px;
}

.project-info p {
  color: var(--text-secondary);
  font-size: 0.95rem;
  margin-bottom: 18px;
  line-height: 1.6;
}

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

.project-tags span {
  padding: 6px 14px;
  background: rgba(102, 126, 234, 0.1);
  color: var(--accent-1);
  border-radius: 20px;
  font-size: 0.78rem;
  font-weight: 500;
  border: 1px solid rgba(102, 126, 234, 0.15);
}

/* ===== 11. Publications ===== */
.pub-category {
  margin-bottom: 48px;
}

.pub-category:last-child {
  margin-bottom: 0;
}

.pub-category-title {
  font-size: 1.4rem;
  font-weight: 600;
  margin-bottom: 24px;
  padding-bottom: 12px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.06);
}

.pub-card {
  display: flex;
  gap: 20px;
  background: var(--glass-bg);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  border: 1px solid var(--glass-border);
  padding: 24px 28px;
  margin-bottom: 16px;
  border-radius: var(--radius);
  transition: all var(--transition);
  border-left: 3px solid transparent;
}

.pub-card:hover {
  border-color: rgba(102, 126, 234, 0.12);
  border-left-color: var(--accent-1);
  box-shadow: var(--card-hover-shadow);
  transform: translateX(4px);
}

.pub-badge {
  flex-shrink: 0;
  padding: 6px 16px;
  border-radius: 6px;
  font-size: 0.75rem;
  font-weight: 700;
  color: #fff;
  height: fit-content;
  white-space: nowrap;
  margin-top: 2px;
}

.pub-badge.conference {
  background: linear-gradient(135deg, #667eea, #764ba2);
}

.pub-badge.journal {
  background: linear-gradient(135deg, #f093fb, #f5576c);
}

.pub-badge.patent {
  background: linear-gradient(135deg, #4facfe, #00f2fe);
}

.pub-body {
  flex: 1;
  min-width: 0;
}

.pub-body h4 {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 8px;
  line-height: 1.4;
}

.pub-authors {
  font-size: 0.9rem;
  color: var(--text-secondary);
  margin-bottom: 4px;
}

.pub-venue {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 12px;
}

.pub-level {
  display: inline-block;
  padding: 2px 10px;
  background: rgba(102, 126, 234, 0.15);
  color: var(--accent-1);
  border-radius: 4px;
  font-size: 0.75rem;
  font-weight: 600;
  margin-left: 4px;
}

.pub-links {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.pub-link {
  display: inline-block;
  padding: 4px 14px;
  background: rgba(102, 126, 234, 0.1);
  color: var(--accent-1);
  border-radius: 16px;
  font-size: 0.78rem;
  font-weight: 600;
  transition: all var(--transition);
  border: 1px solid rgba(102, 126, 234, 0.12);
}

.pub-link:hover {
  background: var(--accent-gradient);
  color: #fff;
  border-color: transparent;
}

/* ===== 12. Contact ===== */
.contact-content {
  max-width: 500px;
  margin: 0 auto;
  text-align: center;
}

.contact-intro {
  font-size: 1.1rem;
  color: var(--text-secondary);
  margin-bottom: 36px;
}

.contact-links {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.contact-item {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 14px;
  padding: 18px 28px;
  background: var(--glass-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius);
  transition: all var(--transition);
  font-size: 1rem;
  font-weight: 500;
}

.contact-item:hover {
  transform: translateY(-4px);
  border-color: rgba(102, 126, 234, 0.2);
  box-shadow: var(--card-hover-shadow);
}

.contact-icon {
  font-size: 1.5rem;
}

/* ===== 13. Footer ===== */
.footer {
  text-align: center;
  padding: 32px 0;
  border-top: 1px solid rgba(255, 255, 255, 0.06);
  color: var(--text-muted);
  font-size: 0.9rem;
}

/* ===== 14. Scroll Reveal ===== */
[data-reveal] {
  opacity: 0;
  transform: translateY(35px);
  transition: opacity 0.7s ease, transform 0.7s cubic-bezier(0.4, 0, 0.2, 1);
}

[data-reveal].revealed {
  opacity: 1;
  transform: translateY(0);
}

[data-reveal-delay="100"] { transition-delay: 0.1s; }
[data-reveal-delay="200"] { transition-delay: 0.2s; }
[data-reveal-delay="300"] { transition-delay: 0.3s; }
[data-reveal-delay="400"] { transition-delay: 0.4s; }
[data-reveal-delay="500"] { transition-delay: 0.5s; }

/* ===== 15. Keyframes ===== */
@keyframes float-orb1 {
  0%, 100%   { transform: translate(0, 0) scale(1); }
  33%        { transform: translate(40px, -40px) scale(1.1); }
  66%        { transform: translate(-20px, 30px) scale(0.9); }
}

@keyframes float-orb2 {
  0%, 100%   { transform: translate(0, 0) scale(1); }
  33%        { transform: translate(-50px, 40px) scale(1.15); }
  66%        { transform: translate(30px, -30px) scale(0.85); }
}

@keyframes float-orb3 {
  0%, 100%   { transform: translate(0, 0) scale(1); }
  50%        { transform: translate(0, -30px) scale(1.1); }
}

@keyframes blink {
  0%, 100%   { opacity: 1; }
  50%        { opacity: 0; }
}

@keyframes gradient-shift {
  0%   { background-position: 0% 50%; }
  50%  { background-position: 100% 50%; }
  100% { background-position: 0% 50%; }
}

/* ===== 16. Responsive ===== */
@media (max-width: 768px) {
  .nav-links {
    display: none;
    position: absolute;
    top: 70px;
    left: 0;
    right: 0;
    background: rgba(10, 10, 15, 0.95);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    flex-direction: column;
    padding: 24px;
    border-bottom: 1px solid var(--glass-border);
    gap: 20px;
  }

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

  .nav-links a {
    font-size: 1rem;
  }

  .menu-toggle {
    display: block;
  }

  .hero h1 {
    font-size: 2.2rem;
  }

  .subtitle {
    font-size: 1.05rem;
  }

  .description {
    font-size: 1rem;
  }

  .section {
    padding: 70px 0;
  }

  .section-title {
    font-size: 1.8rem;
    margin-bottom: 40px;
  }

  .about-stats {
    gap: 32px;
    padding: 28px 24px;
    flex-wrap: wrap;
  }

  .stat-number {
    font-size: 2.2rem;
  }

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

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

  .pub-card {
    flex-direction: column;
    gap: 12px;
    padding: 20px;
  }

  .pub-badge {
    align-self: flex-start;
  }

  .contact-links {
    gap: 14px;
  }
}

@media (max-width: 480px) {
  .hero h1 {
    font-size: 1.8rem;
  }

  .hero-avatar {
    width: 80px;
    height: 80px;
    margin-bottom: 28px;
  }

  .avatar-initials {
    font-size: 1.5rem;
  }

  .btn {
    padding: 12px 28px;
    font-size: 0.85rem;
  }

  .about-stats {
    flex-direction: column;
    gap: 24px;
  }

  .section {
    padding: 50px 0;
  }

  .project-card:hover {
    transform: translateY(-4px);
  }
}