/* ============================================
   Md Mushfique Rahman — Academic Portfolio
   ============================================ */

:root {
  --color-bg: #ffffff;
  --color-bg-alt: #f7f9fc;
  --color-text: #1a1a2e;
  --color-text-muted: #4a5568;
  --color-text-light: #718096;
  --color-accent: #1e3a5f;
  --color-accent-hover: #2c5282;
  --color-accent-light: #ebf4ff;
  --color-border: #e2e8f0;
  --color-card-shadow: rgba(30, 58, 95, 0.08);

  --font-sans: 'Inter', system-ui, -apple-system, sans-serif;
  --font-serif: 'Source Serif 4', Georgia, serif;

  --header-height: 64px;
  --container-max: 1100px;
  --radius: 8px;
  --radius-lg: 12px;
  --transition: 0.2s ease;
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-height) + 16px);
}

body {
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.65;
  color: var(--color-text);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
}

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

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color var(--transition);
}

a:hover {
  color: var(--color-accent-hover);
}

ul {
  list-style: none;
}

.container {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 24px;
}

/* ---- Header / Nav ---- */

.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  height: var(--header-height);
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--color-border);
  transition: box-shadow var(--transition);
}

.site-header.scrolled {
  box-shadow: 0 2px 12px var(--color-card-shadow);
}

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

.nav-logo {
  font-family: var(--font-serif);
  font-weight: 700;
  font-size: 1.15rem;
  color: var(--color-accent);
  letter-spacing: -0.02em;
}

.nav-logo:hover {
  color: var(--color-accent-hover);
}

.nav-menu {
  display: flex;
  align-items: center;
  gap: 4px;
}

.nav-link {
  display: block;
  padding: 8px 12px;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-text-muted);
  border-radius: var(--radius);
  transition: color var(--transition), background var(--transition);
}

.nav-link:hover,
.nav-link.active {
  color: var(--color-accent);
  background: var(--color-accent-light);
}

.nav-link--cta {
  color: #fff;
  background: var(--color-accent);
  margin-left: 4px;
}

.nav-link--cta:hover,
.nav-link--cta.active {
  color: #fff;
  background: var(--color-accent-hover);
}

.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 40px;
  height: 40px;
  padding: 8px;
  background: none;
  border: none;
  cursor: pointer;
  border-radius: var(--radius);
}

.nav-toggle-bar {
  display: block;
  width: 100%;
  height: 2px;
  background: var(--color-accent);
  border-radius: 2px;
  transition: transform var(--transition), opacity var(--transition);
}

.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);
}

/* ---- Buttons ---- */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 24px;
  font-family: var(--font-sans);
  font-size: 0.9375rem;
  font-weight: 600;
  line-height: 1;
  border-radius: var(--radius);
  border: 2px solid transparent;
  cursor: pointer;
  transition: background var(--transition), color var(--transition), border-color var(--transition);
  text-decoration: none;
}

.btn-primary {
  background: var(--color-accent);
  color: #fff;
  border-color: var(--color-accent);
}

.btn-primary:hover {
  background: var(--color-accent-hover);
  border-color: var(--color-accent-hover);
  color: #fff;
}

.btn-secondary {
  background: var(--color-accent-light);
  color: var(--color-accent);
  border-color: var(--color-accent-light);
}

.btn-secondary:hover {
  background: #dbeafe;
  color: var(--color-accent-hover);
}

.btn-outline {
  background: transparent;
  color: var(--color-accent);
  border-color: var(--color-accent);
}

.btn-outline:hover {
  background: var(--color-accent);
  color: #fff;
}

.btn-lg {
  padding: 16px 32px;
  font-size: 1rem;
}

.btn-icon {
  flex-shrink: 0;
}

/* ---- Hero ---- */

.hero {
  padding: calc(var(--header-height) + 64px) 0 80px;
  background: linear-gradient(180deg, var(--color-bg-alt) 0%, var(--color-bg) 100%);
}

.hero-inner {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 48px;
  align-items: center;
}

.hero-greeting {
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--color-accent);
  letter-spacing: 0.04em;
  text-transform: uppercase;
  margin-bottom: 8px;
}

.hero-name {
  font-family: var(--font-serif);
  font-size: clamp(2rem, 5vw, 2.75rem);
  font-weight: 700;
  line-height: 1.15;
  color: var(--color-text);
  letter-spacing: -0.02em;
  margin-bottom: 12px;
}

.hero-title {
  font-size: 1.125rem;
  font-weight: 500;
  color: var(--color-text-muted);
  margin-bottom: 20px;
}

.hero-intro {
  font-size: 1.0625rem;
  color: var(--color-text-muted);
  max-width: 540px;
  margin-bottom: 32px;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.hero-image img {
  width: 280px;
  height: 280px;
  border-radius: 50%;
  object-fit: cover;
  border: 4px solid var(--color-border);
  box-shadow: 0 8px 32px var(--color-card-shadow);
}

/* ---- Sections ---- */

.section {
  padding: 80px 0;
}

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

.section-title {
  font-family: var(--font-serif);
  font-size: clamp(1.5rem, 3vw, 1.875rem);
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 12px;
  letter-spacing: -0.02em;
}

.section-subtitle {
  font-size: 1.0625rem;
  color: var(--color-text-muted);
  max-width: 640px;
  margin-bottom: 40px;
}

/* ---- About ---- */

.about-grid {
  display: grid;
  grid-template-columns: 1fr 300px;
  gap: 48px;
  align-items: start;
}

.about-text p {
  color: var(--color-text-muted);
  margin-bottom: 16px;
}

.about-text p:last-child {
  margin-bottom: 0;
}

.about-interests {
  padding: 16px 20px;
  background: var(--color-accent-light);
  border-left: 3px solid var(--color-accent);
  border-radius: 0 var(--radius) var(--radius) 0;
  margin-top: 8px !important;
  color: var(--color-text) !important;
}

.about-facts {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 24px;
}

.section-alt + .section .about-facts,
.section + .section-alt .about-facts {
  background: var(--color-bg);
}

.about-facts-title {
  font-size: 0.8125rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-accent);
  margin-bottom: 16px;
}

.facts-item {
  padding: 12px 0;
  border-bottom: 1px solid var(--color-border);
}

.facts-item:last-child {
  border-bottom: none;
  padding-bottom: 0;
}

.facts-item dt {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text-light);
  margin-bottom: 4px;
}

.facts-item dd {
  font-size: 0.9375rem;
  color: var(--color-text);
  line-height: 1.5;
}

/* ---- Cards ---- */

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(min(100%, 300px), 1fr));
  gap: 24px;
}

.card {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 28px;
  transition: box-shadow var(--transition), border-color var(--transition);
}

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

.card:hover {
  box-shadow: 0 8px 24px var(--color-card-shadow);
  border-color: #cbd5e0;
}

.card-meta {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 12px;
}

.card-date {
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--color-text-light);
}

.card-tag {
  font-size: 0.6875rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 3px 8px;
  border-radius: 4px;
  background: var(--color-accent-light);
  color: var(--color-accent);
}

.card-tag--presented {
  background: #f0fff4;
  color: #276749;
}

.card-title {
  font-family: var(--font-serif);
  font-size: 1.125rem;
  font-weight: 700;
  line-height: 1.35;
  color: var(--color-text);
  margin-bottom: 6px;
}

.card-subtitle {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-accent);
  margin-bottom: 8px;
}

.card-org {
  font-size: 0.875rem;
  font-style: italic;
  color: var(--color-text-light);
  margin-bottom: 12px;
}

.card-stack {
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--color-accent);
  margin-bottom: 12px;
}

.card-desc {
  font-size: 0.9375rem;
  color: var(--color-text-muted);
  line-height: 1.6;
}

.card-keywords {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-top: 16px;
}

.card-keywords li {
  font-size: 0.75rem;
  font-weight: 500;
  padding: 4px 10px;
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: 20px;
  color: var(--color-text-muted);
}

.projects-github {
  margin-top: 32px;
  font-size: 0.9375rem;
  color: var(--color-text-muted);
}

.projects-github a {
  font-weight: 600;
}

/* ---- Timeline ---- */

.timeline {
  position: relative;
  padding-left: 28px;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 6px;
  top: 8px;
  bottom: 8px;
  width: 2px;
  background: var(--color-border);
}

.timeline-item {
  position: relative;
  padding-bottom: 36px;
}

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

.timeline-marker {
  position: absolute;
  left: -28px;
  top: 6px;
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: var(--color-bg);
  border: 3px solid var(--color-accent);
}

.timeline-header {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: baseline;
  gap: 8px 16px;
  margin-bottom: 4px;
}

.timeline-title {
  font-size: 1rem;
  font-weight: 600;
  color: var(--color-text);
  line-height: 1.4;
  flex: 1;
  min-width: 200px;
}

.timeline-date {
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--color-text-light);
  white-space: nowrap;
}

.timeline-org {
  font-size: 0.875rem;
  font-style: italic;
  color: var(--color-text-light);
  margin-bottom: 8px;
}

.timeline-desc {
  font-size: 0.9375rem;
  color: var(--color-text-muted);
  line-height: 1.6;
}

/* ---- Skills ---- */

.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(min(100%, 280px), 1fr));
  gap: 24px;
}

.skill-group {
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 24px;
}

.section-alt + .section .skill-group {
  background: var(--color-bg-alt);
}

.skill-group-title {
  font-size: 0.8125rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-accent);
  margin-bottom: 14px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--color-border);
}

.skill-list {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.skill-list li {
  font-size: 0.875rem;
  font-weight: 500;
  padding: 6px 12px;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  color: var(--color-text-muted);
}

/* ---- Awards ---- */

.awards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(min(100%, 280px), 1fr));
  gap: 32px;
}

.awards-heading {
  font-size: 0.9375rem;
  font-weight: 600;
  color: var(--color-accent);
  margin-bottom: 16px;
}

.awards-list li {
  position: relative;
  padding-left: 18px;
  margin-bottom: 10px;
  font-size: 0.9375rem;
  color: var(--color-text-muted);
  line-height: 1.5;
}

.awards-list li::before {
  content: '';
  position: absolute;
  left: 0;
  top: 10px;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--color-accent);
}

/* ---- CV Section ---- */

.cv-section {
  text-align: center;
}

.cv-inner .section-subtitle {
  margin-left: auto;
  margin-right: auto;
}

/* ---- Contact ---- */

.contact-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 16px;
}

.contact-card {
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding: 20px 24px;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  transition: box-shadow var(--transition), border-color var(--transition);
  text-decoration: none;
}

.contact-card:hover {
  box-shadow: 0 4px 16px var(--color-card-shadow);
  border-color: var(--color-accent);
}

.contact-card--static {
  cursor: default;
}

.contact-card--static:hover {
  box-shadow: none;
  border-color: var(--color-border);
}

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

.contact-value {
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--color-accent);
  word-break: break-word;
}

.contact-card--static .contact-value {
  color: var(--color-text);
}

/* ---- Contact Page ---- */

.contact-main {
  padding: calc(var(--header-height) + 48px) 0 80px;
  min-height: calc(100vh - var(--header-height) - 80px);
}

.contact-container {
  max-width: 820px;
}

.contact-page-title {
  font-family: var(--font-serif);
  font-size: clamp(2.25rem, 5vw, 3rem);
  font-weight: 700;
  color: var(--color-text);
  letter-spacing: -0.02em;
  margin-bottom: 16px;
}

.contact-page-intro {
  font-size: 1.0625rem;
  color: var(--color-text-muted);
  line-height: 1.65;
  margin-bottom: 40px;
  max-width: 560px;
}

.contact-inline-link {
  color: var(--color-accent);
  font-weight: 500;
  text-decoration: underline;
  text-underline-offset: 3px;
}

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

.contact-layout {
  display: grid;
  grid-template-columns: 1fr 200px;
  gap: 48px 64px;
  align-items: start;
}

.contact-form {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.form-label {
  font-size: 0.9375rem;
  font-weight: 600;
  color: var(--color-text);
}

.form-input,
.form-textarea {
  width: 100%;
  padding: 12px 14px;
  font-family: var(--font-sans);
  font-size: 0.9375rem;
  color: var(--color-text);
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  transition: border-color var(--transition), box-shadow var(--transition);
}

.form-input:focus,
.form-textarea:focus {
  outline: none;
  border-color: var(--color-accent);
  box-shadow: 0 0 0 3px rgba(30, 58, 95, 0.12);
}

.form-textarea {
  resize: vertical;
  min-height: 140px;
  line-height: 1.5;
}

.btn-full {
  width: 100%;
  margin-top: 4px;
}

.contact-links {
  padding-top: 36px;
}

.contact-links-list {
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.contact-links-list a {
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--color-accent);
  text-decoration: none;
}

.contact-links-list a:hover {
  color: var(--color-accent-hover);
  text-decoration: underline;
  text-underline-offset: 3px;
}

@media (max-width: 768px) {
  .contact-layout {
    grid-template-columns: 1fr;
    gap: 32px;
  }

  .contact-links {
    padding-top: 0;
    border-top: 1px solid var(--color-border);
    padding-top: 24px;
  }

  .contact-links-list {
    flex-direction: row;
    flex-wrap: wrap;
    gap: 16px 24px;
  }
}

/* ---- Footer ---- */

.site-footer {
  padding: 32px 0;
  border-top: 1px solid var(--color-border);
  background: var(--color-bg);
}

.footer-inner {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
}

.footer-inner p {
  font-size: 0.875rem;
  color: var(--color-text-light);
}

.footer-inner nav {
  display: flex;
  gap: 20px;
}

.footer-inner nav a {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-text-muted);
}

.footer-inner nav a:hover {
  color: var(--color-accent);
}

/* ---- Responsive ---- */

@media (max-width: 900px) {
  .hero-inner {
    grid-template-columns: 1fr;
    text-align: center;
  }

  .hero-intro {
    margin-left: auto;
    margin-right: auto;
  }

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

  .hero-image {
    order: -1;
  }

  .hero-image img {
    width: 200px;
    height: 200px;
    margin: 0 auto;
  }

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

@media (max-width: 1024px) {
  .nav-toggle {
    display: flex;
  }

  .nav-menu {
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: 12px 16px 20px;
    background: rgba(255, 255, 255, 0.98);
    backdrop-filter: blur(8px);
    border-bottom: 1px solid var(--color-border);
    box-shadow: 0 8px 24px var(--color-card-shadow);
    transform: translateY(-110%);
    opacity: 0;
    visibility: hidden;
    transition: transform 0.25s ease, opacity 0.25s ease, visibility 0.25s;
  }

  .nav-menu.open {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
  }

  .nav-link {
    padding: 12px 16px;
    font-size: 1rem;
  }

  .nav-link--cta {
    margin-left: 0;
    margin-top: 4px;
    text-align: center;
  }
}

@media (max-width: 768px) {
  .section {
    padding: 60px 0;
  }

  .hero {
    padding-top: calc(var(--header-height) + 40px);
    padding-bottom: 60px;
  }

  .contact-main {
    padding-top: calc(var(--header-height) + 32px);
    padding-bottom: 60px;
  }

  .timeline-header {
    flex-direction: column;
    align-items: flex-start;
  }

  .timeline-date {
    white-space: normal;
  }

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

  .footer-inner {
    flex-direction: column;
    text-align: center;
  }

  .footer-inner nav {
    justify-content: center;
  }
}

@media (max-width: 480px) {
  .container {
    padding: 0 16px;
  }

  .hero-actions {
    flex-direction: column;
    width: 100%;
  }

  .hero-actions .btn {
    width: 100%;
  }

  .btn-lg {
    width: 100%;
  }
}

/* ---- Accessibility ---- */

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *, *::before, *::after {
    transition-duration: 0.01ms !important;
  }
}

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

.nav-toggle:focus-visible,
.btn:focus-visible {
  outline-offset: 3px;
}