/* ================================================
   Luân Võ — Personal Site
   Pure CSS, no framework. Mobile-first.
   ================================================ */

/* --- Custom Properties --- */
:root {
  --font-heading: 'Space Grotesk', system-ui, sans-serif;
  --font-body: 'Inter', system-ui, sans-serif;

  /* Spacing */
  --space-xs: 0.5rem;
  --space-sm: 1rem;
  --space-md: 1.5rem;
  --space-lg: 2.5rem;
  --space-xl: 4rem;
  --space-2xl: 6rem;

  --nav-height: 64px;
  --max-width: 1100px;
  --radius: 12px;
  --radius-sm: 8px;
  --radius-pill: 100px;
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* --- Theme: Dark (default) --- */
[data-theme="dark"] {
  --bg-primary: #0f1117;
  --bg-secondary: #161922;
  --bg-card: #1c1f2e;
  --bg-card-hover: #242838;
  --text-primary: #e8eaf0;
  --text-secondary: #9ca3b4;
  --text-muted: #6b7280;
  --accent: #22d3a7;
  --accent-glow: rgba(34, 211, 167, 0.15);
  --accent-hover: #1ab892;
  --border: rgba(255, 255, 255, 0.06);
  --border-strong: rgba(255, 255, 255, 0.12);
  --pill-bg: rgba(34, 211, 167, 0.1);
  --pill-text: #22d3a7;
  --shadow-card: 0 4px 24px rgba(0, 0, 0, 0.3);
  --shadow-hover: 0 8px 40px rgba(0, 0, 0, 0.4);
  --hero-gradient: radial-gradient(ellipse at 50% 0%, rgba(34, 211, 167, 0.08) 0%, transparent 60%);
  --nav-bg: rgba(15, 17, 23, 0.85);
  --dot-color: rgba(255, 255, 255, 0.04);
}

/* --- Theme: Light --- */
[data-theme="light"] {
  --bg-primary: #fafbfc;
  --bg-secondary: #f0f2f5;
  --bg-card: #ffffff;
  --bg-card-hover: #f8f9fa;
  --text-primary: #1a1d2b;
  --text-secondary: #5a6070;
  --text-muted: #8b92a0;
  --accent: #0d9373;
  --accent-glow: rgba(13, 147, 115, 0.1);
  --accent-hover: #0b7d63;
  --border: rgba(0, 0, 0, 0.06);
  --border-strong: rgba(0, 0, 0, 0.1);
  --pill-bg: rgba(13, 147, 115, 0.08);
  --pill-text: #0d9373;
  --shadow-card: 0 2px 12px rgba(0, 0, 0, 0.06);
  --shadow-hover: 0 8px 30px rgba(0, 0, 0, 0.1);
  --hero-gradient: radial-gradient(ellipse at 50% 0%, rgba(13, 147, 115, 0.06) 0%, transparent 60%);
  --nav-bg: rgba(250, 251, 252, 0.85);
  --dot-color: rgba(0, 0, 0, 0.04);
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: var(--nav-height);
}

body {
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.6;
  color: var(--text-primary);
  background: var(--bg-primary);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
  transition: background var(--transition), color var(--transition);
}

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

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

ul {
  list-style: none;
}

h1, h2, h3 {
  font-family: var(--font-heading);
  line-height: 1.2;
}

/* --- Container --- */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-md);
}

/* --- Navigation --- */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--nav-height);
  z-index: 100;
  background: var(--nav-bg);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
  transition: background var(--transition), border-color var(--transition);
}

.nav-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-md);
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-sm);
}

.nav-logo {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--accent);
  letter-spacing: -0.5px;
  white-space: nowrap;
}

.nav-links {
  display: none;
  gap: var(--space-xs);
}

.nav-links a {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  padding: 0.4rem 0.75rem;
  border-radius: var(--radius-sm);
  transition: color var(--transition), background var(--transition);
}

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

.theme-toggle {
  background: none;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  cursor: pointer;
  padding: 0.5rem;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: color var(--transition), border-color var(--transition), background var(--transition);
}

.theme-toggle:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-glow);
}

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

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

.nav-hamburger span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--text-secondary);
  border-radius: 2px;
  transition: all var(--transition);
}

.nav-hamburger.active span:nth-child(1) {
  transform: rotate(45deg) translate(5px, 5px);
}
.nav-hamburger.active span:nth-child(2) {
  opacity: 0;
}
.nav-hamburger.active span:nth-child(3) {
  transform: rotate(-45deg) translate(5px, -5px);
}

/* Mobile Menu */
.mobile-menu {
  position: fixed;
  top: var(--nav-height);
  left: 0;
  right: 0;
  background: var(--nav-bg);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
  padding: var(--space-sm) var(--space-md);
  display: flex;
  flex-direction: column;
  gap: 4px;
  z-index: 99;
  transform: translateY(-100%);
  opacity: 0;
  pointer-events: none;
  transition: transform var(--transition), opacity var(--transition);
}

.mobile-menu.open {
  transform: translateY(0);
  opacity: 1;
  pointer-events: auto;
}

.mobile-menu a {
  font-size: 1rem;
  font-weight: 500;
  color: var(--text-secondary);
  padding: 0.75rem 1rem;
  border-radius: var(--radius-sm);
  transition: color var(--transition), background var(--transition);
}

.mobile-menu a:hover {
  color: var(--text-primary);
  background: var(--accent-glow);
}

/* --- Hero --- */
.hero {
  min-height: 100vh;
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  position: relative;
  padding: calc(var(--nav-height) + var(--space-lg)) var(--space-md) var(--space-xl);
  background: var(--hero-gradient);
  overflow: hidden;
}

.hero-bg-grid {
  position: absolute;
  inset: 0;
  background-image:
    radial-gradient(circle, var(--dot-color) 1px, transparent 1px);
  background-size: 32px 32px;
  mask-image: radial-gradient(ellipse at center, black 30%, transparent 70%);
  -webkit-mask-image: radial-gradient(ellipse at center, black 30%, transparent 70%);
}

.hero-content {
  position: relative;
  z-index: 1;
}

.hero-avatar {
  position: relative;
  width: 160px;
  height: 160px;
  margin: 0 auto var(--space-lg);
}

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

.hero-avatar-ring {
  position: absolute;
  inset: -8px;
  border-radius: 50%;
  border: 2px dashed var(--accent);
  opacity: 0.3;
  animation: spin 20s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

.hero-name {
  font-size: clamp(2.5rem, 6vw, 4rem);
  font-weight: 700;
  letter-spacing: -1px;
  margin-bottom: var(--space-xs);
}

.hero-title {
  font-size: clamp(1rem, 2.5vw, 1.25rem);
  color: var(--accent);
  font-weight: 500;
  margin-bottom: var(--space-sm);
}

.hero-tagline {
  font-size: clamp(0.95rem, 2vw, 1.1rem);
  color: var(--text-secondary);
  max-width: 480px;
  margin: 0 auto var(--space-lg);
}

.hero-cta {
  display: flex;
  gap: var(--space-sm);
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: var(--space-lg);
}

.btn {
  font-family: var(--font-heading);
  font-size: 0.9rem;
  font-weight: 600;
  padding: 0.75rem 1.75rem;
  border-radius: var(--radius-pill);
  cursor: pointer;
  transition: all var(--transition);
  border: none;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}

.btn-primary {
  background: var(--accent);
  color: #0f1117;
}

.btn-primary:hover {
  background: var(--accent-hover);
  transform: translateY(-2px);
  box-shadow: 0 8px 24px var(--accent-glow);
}

.btn-ghost {
  background: transparent;
  color: var(--text-primary);
  border: 1px solid var(--border-strong);
}

.btn-ghost:hover {
  border-color: var(--accent);
  color: var(--accent);
  background: var(--accent-glow);
}

/* Hero Social Icons */
.hero-socials {
  display: flex;
  justify-content: center;
  gap: 0.75rem;
  margin-bottom: var(--space-lg);
}

.hero-socials a {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  border: 1px solid var(--border-strong);
  color: var(--text-secondary);
  transition: all var(--transition);
}

.hero-socials a:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-glow);
  transform: translateY(-3px);
}

.hero-location {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  font-size: 0.9rem;
  color: var(--text-muted);
}

/* --- Scroll Hint (all sections) --- */
.scroll-hint {
  display: flex;
  justify-content: center;
  padding-top: var(--space-lg);
  color: var(--text-muted);
  animation: bounce 2s infinite;
  transition: color var(--transition);
}

.scroll-hint:hover {
  color: var(--accent);
}

.hero .scroll-hint {
  position: absolute;
  bottom: var(--space-lg);
  left: 50%;
  transform: translateX(-50%);
  padding-top: 0;
}

/* --- Back to Top --- */
.back-to-top {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  z-index: 90;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  border: 1px solid var(--border-strong);
  background: var(--bg-card);
  color: var(--text-secondary);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  pointer-events: none;
  transform: translateY(12px);
  transition: all var(--transition);
  box-shadow: var(--shadow-card);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
}

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

.back-to-top:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-glow);
  transform: translateY(-2px);
}

@keyframes bounce {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(8px); }
}

/* --- Sections --- */
.section {
  padding: var(--space-2xl) 0;
}

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

.section-title {
  font-size: clamp(1.75rem, 4vw, 2.5rem);
  font-weight: 700;
  letter-spacing: -0.5px;
  margin-bottom: var(--space-xs);
  text-align: center;
}

.section-subtitle {
  text-align: center;
  color: var(--text-secondary);
  font-size: 1rem;
  margin-bottom: var(--space-xl);
  max-width: 520px;
  margin-left: auto;
  margin-right: auto;
}

/* --- Reveal Animation --- */
.reveal {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.6s ease-out, transform 0.6s ease-out;
}

.reveal.visible {
  opacity: 1;
  transform: translateY(0);
}

/* --- About --- */
.about-grid {
  display: grid;
  gap: var(--space-xl);
  margin-top: var(--space-lg);
}

.about-text p {
  color: var(--text-secondary);
  margin-bottom: var(--space-sm);
  font-size: 1.05rem;
}

.about-text strong {
  color: var(--text-primary);
}

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

.stat-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--space-md);
  text-align: center;
  transition: border-color var(--transition), box-shadow var(--transition);
}

.stat-card:hover {
  border-color: var(--accent);
  box-shadow: 0 0 24px var(--accent-glow);
}

.stat-number {
  display: block;
  font-family: var(--font-heading);
  font-size: 2rem;
  font-weight: 700;
  color: var(--accent);
  line-height: 1;
  margin-bottom: 0.25rem;
}

.stat-label {
  font-size: 0.8rem;
  color: var(--text-muted);
  font-weight: 500;
}

/* --- Timeline --- */
.timeline {
  position: relative;
  margin-top: var(--space-lg);
  padding-left: 28px;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 6px;
  top: 8px;
  bottom: 8px;
  width: 2px;
  background: linear-gradient(to bottom, var(--accent), var(--border));
  border-radius: 2px;
}

.timeline-item {
  position: relative;
  padding-bottom: var(--space-lg);
}

.timeline-item:last-child {
  padding-bottom: 0;
}

.timeline-dot {
  position: absolute;
  left: -24px;
  top: 8px;
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: var(--bg-primary);
  border: 3px solid var(--accent);
  z-index: 1;
  transition: background var(--transition);
}

.timeline-item:hover .timeline-dot {
  background: var(--accent);
}

.timeline-content {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--space-md);
  transition: border-color var(--transition), box-shadow var(--transition);
}

.timeline-item:hover .timeline-content {
  border-color: var(--accent);
  box-shadow: 0 0 24px var(--accent-glow);
}

.timeline-header {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
  margin-bottom: 0.5rem;
}

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

.timeline-date {
  font-size: 0.8rem;
  color: var(--accent);
  font-weight: 600;
  font-family: var(--font-heading);
}

.timeline-role {
  font-size: 0.9rem;
  color: var(--text-secondary);
  font-style: italic;
  margin-bottom: 0.75rem;
}

.timeline-details {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.timeline-details li {
  font-size: 0.875rem;
  color: var(--text-secondary);
  padding-left: 1rem;
  position: relative;
}

.timeline-details li::before {
  content: '▸';
  position: absolute;
  left: 0;
  color: var(--accent);
  font-size: 0.8rem;
}

/* --- Skills --- */
.skills-grid {
  display: grid;
  gap: var(--space-md);
  margin-top: var(--space-lg);
}

.skill-category {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--space-md);
  transition: border-color var(--transition);
}

.skill-category:hover {
  border-color: var(--accent);
}

.skill-category h3 {
  font-size: 0.95rem;
  font-weight: 600;
  margin-bottom: var(--space-sm);
  display: flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--text-primary);
}

.skill-category h3 svg {
  color: var(--accent);
  flex-shrink: 0;
}

.skill-pills {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.pill {
  font-size: 0.8rem;
  font-weight: 500;
  padding: 0.35rem 0.85rem;
  border-radius: var(--radius-pill);
  background: var(--pill-bg);
  color: var(--pill-text);
  border: 1px solid transparent;
  transition: border-color var(--transition), background var(--transition);
}

.pill:hover {
  border-color: var(--accent);
  background: var(--accent-glow);
}

/* --- Certifications --- */
.certs {
  margin-top: var(--space-xl);
}

.certs-title {
  font-size: 1.25rem;
  font-weight: 600;
  text-align: center;
  margin-bottom: var(--space-md);
}

.certs-grid {
  display: grid;
  gap: var(--space-sm);
  max-width: 600px;
  margin: 0 auto;
}

.cert-card {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--space-md);
  transition: border-color var(--transition), box-shadow var(--transition);
}

.cert-card:hover {
  border-color: var(--accent);
  box-shadow: 0 0 24px var(--accent-glow);
  transform: translateY(-2px);
}

a.cert-card {
  text-decoration: none;
  color: inherit;
}

.cert-badge {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--accent);
  background: var(--pill-bg);
  width: 56px;
  height: 56px;
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.cert-info strong {
  display: block;
  font-size: 0.9rem;
  margin-bottom: 0.15rem;
}

.cert-info span {
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* --- Portfolio --- */
.portfolio-grid {
  display: grid;
  gap: var(--space-md);
}

.project-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--space-md);
  display: block;
  transition: all var(--transition);
  position: relative;
  overflow: hidden;
}

.project-card::after {
  content: '→';
  position: absolute;
  top: var(--space-md);
  right: var(--space-md);
  font-size: 1.25rem;
  color: var(--text-muted);
  transition: color var(--transition), transform var(--transition);
}

.project-card:hover {
  border-color: var(--accent);
  box-shadow: var(--shadow-hover);
  transform: translateY(-4px);
}

.project-card:hover::after {
  color: var(--accent);
  transform: translateX(4px);
}

.project-icon {
  color: var(--accent);
  margin-bottom: var(--space-sm);
}

.project-card h3 {
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
  padding-right: 2rem;
}

.project-card p {
  font-size: 0.875rem;
  color: var(--text-secondary);
  margin-bottom: var(--space-sm);
  line-height: 1.5;
}

.project-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
}

.project-tags span {
  font-size: 0.75rem;
  font-weight: 500;
  padding: 0.2rem 0.6rem;
  border-radius: var(--radius-pill);
  background: var(--pill-bg);
  color: var(--pill-text);
}

/* --- Hobbies --- */
.hobbies-grid {
  display: grid;
  gap: var(--space-md);
}

.hobby-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--space-lg) var(--space-md);
  text-align: center;
  transition: border-color var(--transition), transform var(--transition), box-shadow var(--transition);
}

.hobby-card:hover {
  border-color: var(--accent);
  transform: translateY(-4px);
  box-shadow: var(--shadow-hover);
}

.hobby-icon {
  color: var(--accent);
  margin-bottom: var(--space-sm);
  display: inline-flex;
}

.hobby-card h3 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 0.4rem;
}

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

/* --- Contact --- */
.contact-grid {
  display: grid;
  gap: var(--space-sm);
  max-width: 600px;
  margin: 0 auto;
}

.contact-card {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--space-sm) var(--space-md);
  transition: all var(--transition);
}

.contact-card:hover {
  border-color: var(--accent);
  background: var(--bg-card-hover);
  transform: translateX(4px);
}

.contact-card svg {
  color: var(--accent);
  flex-shrink: 0;
}

.contact-card span {
  font-size: 0.9rem;
  font-weight: 500;
}

/* --- Footer --- */
.footer {
  padding: var(--space-lg) 0;
  text-align: center;
  border-top: 1px solid var(--border);
}

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

/* ==============================================
   RESPONSIVE BREAKPOINTS
   ============================================== */

/* Tablet (640px+) */
@media (min-width: 640px) {
  .about-grid {
    grid-template-columns: 1.2fr 1fr;
    align-items: start;
  }

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

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

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

  .contact-grid {
    grid-template-columns: repeat(2, 1fr);
    max-width: 100%;
  }

  .certs-grid {
    grid-template-columns: repeat(2, 1fr);
    max-width: 100%;
  }

  .timeline-header {
    flex-direction: row;
    align-items: center;
    justify-content: space-between;
    gap: var(--space-sm);
  }
}

/* Desktop (1024px+) */
@media (min-width: 1024px) {
  .nav-links {
    display: flex;
  }

  .nav-hamburger {
    display: none;
  }

  .mobile-menu {
    display: none !important;
  }

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

  .hobbies-grid {
    grid-template-columns: repeat(4, 1fr);
  }

  .timeline {
    padding-left: 40px;
  }

  .timeline-dot {
    left: -36px;
  }

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

/* --- Print --- */
@media print {
  .nav, .hero-scroll, .theme-toggle, .nav-hamburger, .mobile-menu { display: none; }
  .section { padding: 2rem 0; }
  .hero { min-height: auto; padding: 2rem 0; }
  .reveal { opacity: 1; transform: none; }
}

/* --- Accessibility --- */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
  html { scroll-behavior: auto; }
  .reveal { opacity: 1; transform: none; }
}

:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}