/* Mohammad Khalooei — academic landing design system */
:root {
  --bg-deep: #070a12;
  --bg-elevated: rgba(15, 23, 42, 0.72);
  --stroke: rgba(148, 163, 184, 0.14);
  --text: #e2e8f0;
  --muted: #94a3b8;
  --accent: #38bdf8;
  --accent-2: #a78bfa;
  --success: #34d399;
  --radius: 14px;
  --radius-lg: 22px;
  --font-sans: Inter, Vazirmatn, "Noto Sans Arabic", ui-sans-serif, system-ui, sans-serif;
  --step--1: clamp(0.82rem, 0.78rem + 0.2vw, 0.9rem);
  --step-0: clamp(0.95rem, 0.88rem + 0.35vw, 1.05rem);
  --step-1: clamp(1.1rem, 1rem + 0.55vw, 1.25rem);
  --step-2: clamp(1.35rem, 1.15rem + 1vw, 1.65rem);
  --step-3: clamp(1.65rem, 1.35rem + 1.6vw, 2.15rem);
  --step-4: clamp(2rem, 1.55rem + 2.4vw, 2.85rem);
  --step-5: clamp(2.45rem, 1.85rem + 3.4vw, 3.6rem);
  --space-xs: 0.35rem;
  --space-sm: 0.65rem;
  --space-md: 1rem;
  --space-lg: 1.75rem;
  --space-xl: 2.75rem;
  --space-2xl: clamp(3rem, 5vw, 5rem);
  --header-h: 72px;
  --max: 1120px;
}

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

html {
  scroll-behavior: smooth;
  background: var(--bg-deep);
}

body {
  margin: 0;
  font-family: Inter, ui-sans-serif, system-ui, sans-serif;
  font-size: var(--step-0);
  line-height: 1.65;
  color: var(--text);
  background: transparent;
  overflow-x: hidden;
}

html[lang="fa"] body {
  font-family: Vazirmatn, Inter, ui-sans-serif, system-ui, sans-serif;
}

html[lang="ar"] body {
  font-family: "Noto Sans Arabic", Vazirmatn, Inter, ui-sans-serif, system-ui, sans-serif;
}

html[lang="zh-CN"] body {
  font-family: Inter, ui-sans-serif, "PingFang SC", "Microsoft YaHei UI", "Hiragino Sans GB",
    "Noto Sans SC", sans-serif;
}

body.rtl {
  font-feature-settings: "kern" 1, "liga" 1;
}

#main,
.site-footer {
  position: relative;
  z-index: 3;
}

a {
  color: var(--accent);
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}

a:hover {
  color: #7dd3fc;
}

:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
}

.skip-link {
  position: absolute;
  left: -999px;
  top: 0;
  background: var(--accent);
  color: #0f172a;
  padding: var(--space-sm) var(--space-md);
  z-index: 9999;
  border-radius: 0 0 var(--radius) 0;
  font-weight: 600;
}

.skip-link:focus {
  left: 0;
}

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

/* Full-viewport starfield — above base bg; mesh/grid are translucent so stars stay visible */
.space-canvas {
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
}

/* Background ambience */
.bg-mesh {
  position: fixed;
  inset: 0;
  z-index: 1;
  pointer-events: none;
  /* No opaque layer here — body/html deep bg shows through; canvas stars remain visible */
  background: radial-gradient(ellipse 120% 80% at 50% -20%, rgba(56, 189, 248, 0.22), transparent 58%),
    radial-gradient(ellipse 90% 60% at 100% 50%, rgba(167, 139, 250, 0.14), transparent 52%),
    radial-gradient(ellipse 70% 50% at 0% 80%, rgba(52, 211, 153, 0.1), transparent 48%);
  animation: mesh-shift 22s ease-in-out infinite alternate;
}

@keyframes mesh-shift {
  0% {
    filter: hue-rotate(0deg) saturate(1);
  }
  100% {
    filter: hue-rotate(18deg) saturate(1.08);
  }
}

.bg-grid {
  position: fixed;
  inset: 0;
  z-index: 2;
  background-image: linear-gradient(rgba(148, 163, 184, 0.06) 1px, transparent 1px),
    linear-gradient(90deg, rgba(148, 163, 184, 0.06) 1px, transparent 1px);
  background-size: 48px 48px;
  mask-image: radial-gradient(ellipse 70% 60% at 50% 40%, black 20%, transparent 75%);
  pointer-events: none;
}

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  border-bottom: 1px solid transparent;
  transition: background 0.35s ease, border-color 0.35s ease, backdrop-filter 0.35s ease;
}

.site-header.scrolled {
  background: rgba(7, 10, 18, 0.82);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom-color: var(--stroke);
}

.header-inner {
  width: min(var(--max), 100% - 2rem);
  margin-inline: auto;
  min-height: var(--header-h);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-md);
}

.brand {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  color: var(--text);
  text-decoration: none;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.brand-mark {
  width: 38px;
  height: 38px;
  border-radius: 12px;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  display: grid;
  place-items: center;
  font-size: 1rem;
  color: #0f172a;
  box-shadow: 0 0 0 1px rgba(255, 255, 255, 0.12) inset;
}

.nav-desktop {
  display: none;
  align-items: center;
  gap: var(--space-xs);
}

@media (min-width: 960px) {
  .nav-desktop {
    display: flex;
  }
}

.nav-desktop a {
  color: var(--muted);
  text-decoration: none;
  padding: 0.45rem 0.65rem;
  border-radius: 999px;
  font-size: var(--step--1);
  font-weight: 500;
  transition: color 0.2s, background 0.2s;
}

.nav-desktop a:hover {
  color: var(--text);
  background: rgba(148, 163, 184, 0.1);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.lang-select {
  appearance: none;
  background: var(--bg-elevated);
  border: 1px solid var(--stroke);
  color: var(--text);
  padding: 0.45rem 2rem 0.45rem 0.75rem;
  border-radius: 999px;
  font-size: var(--step--1);
  font-family: inherit;
  cursor: pointer;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' fill='%2394a3b8'%3E%3Cpath d='M6 8L2 4h8z'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 0.65rem center;
}

.nav-toggle {
  display: flex;
  flex-direction: column;
  gap: 5px;
  padding: 0.5rem;
  background: transparent;
  border: 1px solid var(--stroke);
  border-radius: var(--radius);
  cursor: pointer;
}

@media (min-width: 960px) {
  .nav-toggle {
    display: none;
  }
}

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

.nav-panel {
  display: none;
  position: absolute;
  top: 100%;
  left: 0;
  right: 0;
  padding: var(--space-md);
  background: rgba(7, 10, 18, 0.96);
  border-bottom: 1px solid var(--stroke);
  backdrop-filter: blur(12px);
}

.nav-panel.open {
  display: block;
}

.nav-panel nav {
  display: flex;
  flex-direction: column;
  gap: var(--space-xs);
  max-width: var(--max);
  margin: 0 auto;
}

.nav-panel a {
  color: var(--text);
  text-decoration: none;
  padding: 0.65rem;
  border-radius: var(--radius);
}

.nav-panel a:hover {
  background: rgba(148, 163, 184, 0.1);
}

/* Hero */
.hero {
  position: relative;
  min-height: min(92vh, 880px);
  display: flex;
  align-items: center;
  padding-block: var(--space-2xl);
}

.hero-inner {
  position: relative;
  width: min(var(--max), 100% - 2rem);
  margin-inline: auto;
}

.hero-kicker {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  font-size: var(--step--1);
  color: var(--muted);
  margin-bottom: var(--space-md);
  animation: fade-up 0.9s ease both;
}

.hero-kicker::before {
  content: "";
  width: 28px;
  height: 2px;
  background: linear-gradient(90deg, var(--accent), transparent);
  border-radius: 2px;
}

body.rtl .hero-kicker::before {
  background: linear-gradient(270deg, var(--accent), transparent);
}

.hero-title {
  font-size: var(--step-5);
  line-height: 1.08;
  letter-spacing: -0.03em;
  margin: 0 0 var(--space-md);
  background: linear-gradient(120deg, #f8fafc 10%, #bae6fd 45%, #c4b5fd 90%);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  animation: fade-up 0.95s ease 0.08s both;
}

.hero-sub {
  font-size: var(--step-1);
  color: var(--muted);
  max-width: 52ch;
  margin: 0 0 var(--space-xl);
  animation: fade-up 1s ease 0.14s both;
}

.hero-toolbar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-md);
  animation: fade-up 1.05s ease 0.18s both;
}

.hero-toolbar-primary {
  flex: 0 0 auto;
}

.hero-links {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-sm);
}

.hero-links .btn-with-icon svg {
  flex-shrink: 0;
  width: 19px;
  height: 19px;
  opacity: 0.92;
}

.hero-links .btn-secondary:hover svg {
  opacity: 1;
}

.hero-links .btn-with-icon span {
  white-space: nowrap;
}

@keyframes fade-up {
  from {
    opacity: 0;
    transform: translateY(18px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.65rem 1.25rem;
  border-radius: 999px;
  font-weight: 600;
  font-size: var(--step--1);
  text-decoration: none;
  border: 1px solid transparent;
  cursor: pointer;
  transition: transform 0.2s ease, box-shadow 0.2s ease, background 0.2s ease;
}

.btn:active {
  transform: scale(0.98);
}

.btn-primary {
  background: linear-gradient(135deg, var(--accent), #0ea5e9);
  color: #0f172a;
  box-shadow: 0 12px 40px rgba(14, 165, 233, 0.25);
}

.btn-primary:hover {
  box-shadow: 0 16px 48px rgba(14, 165, 233, 0.35);
  color: #0f172a;
}

.btn-secondary {
  background: rgba(148, 163, 184, 0.12);
  border-color: var(--stroke);
  color: var(--text);
}

.btn-secondary:hover {
  background: rgba(148, 163, 184, 0.18);
  color: var(--text);
}

.btn-ghost {
  border-radius: var(--radius);
  border: 1px solid var(--stroke);
  background: rgba(15, 23, 42, 0.5);
  color: var(--text);
}

.btn-ghost:hover {
  border-color: rgba(56, 189, 248, 0.35);
}

/* Sections */
.section {
  padding-block: var(--space-2xl);
  scroll-margin-top: calc(var(--header-h) + 12px);
}

.section-head {
  width: min(var(--max), 100% - 2rem);
  margin-inline: auto;
  margin-bottom: var(--space-xl);
}

.section-head h2 {
  font-size: var(--step-3);
  margin: 0 0 var(--space-sm);
  letter-spacing: -0.02em;
}

.section-head p,
.section-lead {
  margin: 0;
  color: var(--muted);
  max-width: 62ch;
  font-size: var(--step-1);
}

.section-lead:empty,
.pubs-note:empty {
  display: none;
}

.grid {
  width: min(var(--max), 100% - 2rem);
  margin-inline: auto;
  display: grid;
  gap: var(--space-md);
}

.spotlight-grid {
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
}

.teaching-grid {
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
}

.apps-grid,
.bridge-grid {
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}

.themes-grid {
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  margin-bottom: var(--space-xl);
}

.subsection-title {
  width: min(var(--max), 100% - 2rem);
  margin-inline: auto;
  margin: 0 auto var(--space-md);
  font-size: var(--step-2);
  letter-spacing: -0.02em;
  font-weight: 600;
}

.pubs-note {
  width: min(var(--max), 100% - 2rem);
  margin: 0 auto var(--space-md);
  color: var(--muted);
  font-size: var(--step--1);
  max-width: 70ch;
}

.publications-list {
  width: min(var(--max), 100% - 2rem);
  margin: 0 auto;
  padding: 0;
  list-style: none;
  counter-reset: pub;
}

.pub-item {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--space-md);
  padding: var(--space-md) 0;
  border-bottom: 1px solid var(--stroke);
  counter-increment: pub;
}

.pub-item::before {
  content: counter(pub, decimal-leading-zero);
  font-variant-numeric: tabular-nums;
  font-weight: 700;
  color: var(--accent);
  font-size: var(--step--1);
  min-width: 2rem;
  flex-shrink: 0;
}

.pub-main {
  flex: 1;
  min-width: min(100%, 280px);
}

.pub-title {
  display: block;
  font-weight: 600;
  font-size: var(--step-1);
  letter-spacing: -0.01em;
  margin-bottom: var(--space-xs);
}

.pub-venue {
  display: block;
  color: var(--muted);
  font-size: var(--step--1);
}

.pub-link {
  flex-shrink: 0;
  font-weight: 600;
  font-size: var(--step--1);
  white-space: nowrap;
}

.scholar-strip {
  width: min(var(--max), 100% - 2rem);
  margin: var(--space-xl) auto;
}

.scholar-strip-inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-lg);
  padding: var(--space-lg);
  border-radius: var(--radius-lg);
  border: 1px solid var(--stroke);
  background: linear-gradient(125deg, rgba(56, 189, 248, 0.1), rgba(167, 139, 250, 0.06));
}

.scholar-strip-inner h3 {
  margin: 0;
  font-size: var(--step-2);
  flex: 1 1 auto;
  min-width: 12ch;
}

/* Full-page load veil */
.page-loader {
  position: fixed;
  inset: 0;
  z-index: 200;
  display: grid;
  place-items: center;
  background: radial-gradient(ellipse 120% 80% at 50% 20%, rgba(15, 23, 42, 0.94), rgba(7, 10, 18, 0.98));
  transition:
    opacity 0.55s ease,
    visibility 0.55s ease;
}

body.is-loaded .page-loader {
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
}

.page-loader-panel {
  position: relative;
  width: 84px;
  height: 84px;
}

.page-loader-ring {
  position: absolute;
  inset: 0;
  border-radius: 50%;
  border: 2px solid rgba(56, 189, 248, 0.22);
  border-top-color: rgba(125, 211, 252, 0.95);
  border-right-color: rgba(167, 139, 250, 0.35);
  animation: page-loader-spin 1s linear infinite;
}

.page-loader-mark {
  position: absolute;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
  font-size: 1.55rem;
  line-height: 1;
  color: rgba(226, 232, 240, 0.92);
  text-shadow: 0 0 24px rgba(56, 189, 248, 0.45);
  animation: page-loader-pulse 1.5s ease-in-out infinite;
}

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

@keyframes page-loader-pulse {
  0%,
  100% {
    opacity: 1;
    transform: translate(-50%, -50%) scale(1);
  }
  50% {
    opacity: 0.55;
    transform: translate(-50%, -50%) scale(0.92);
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-loader-ring {
    animation: none;
    border-color: rgba(125, 211, 252, 0.45);
  }

  .page-loader-mark {
    animation: none;
  }

  body.is-loaded .page-loader {
    transition-duration: 0.15s;
  }
}

.bridge-card h3 {
  font-size: var(--step-2);
  margin: 0 0 var(--space-sm);
  letter-spacing: -0.02em;
}

.bridge-card p {
  margin: 0 0 var(--space-sm);
  color: var(--muted);
  font-size: var(--step--1);
}

.theme-card h3 {
  font-size: var(--step-2);
  margin: 0 0 var(--space-sm);
  letter-spacing: -0.02em;
}

.theme-card p {
  margin: 0;
  color: var(--muted);
  font-size: var(--step--1);
}

.bridge-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  margin-top: var(--space-sm);
}

.bridge-card .btn-ghost,
.bridge-card .btn-secondary {
  margin-top: 0;
}

.course-link {
  display: inline-flex;
  margin-top: var(--space-md);
  font-weight: 600;
  font-size: var(--step--1);
  text-decoration: none;
  color: var(--accent);
}

.course-link:hover {
  color: #7dd3fc;
}

.card {
  position: relative;
  padding: var(--space-lg);
  border-radius: var(--radius-lg);
  border: 1px solid var(--stroke);
  background: linear-gradient(155deg, rgba(15, 23, 42, 0.85), rgba(15, 23, 42, 0.55));
  backdrop-filter: blur(10px);
  overflow: hidden;
  transition: transform 0.35s ease, border-color 0.35s ease, box-shadow 0.35s ease;
}

.card::before {
  content: "";
  position: absolute;
  inset: 0;
  background: radial-gradient(600px 200px at var(--gx, 80%) var(--gy, 0%), rgba(56, 189, 248, 0.08), transparent 55%);
  opacity: 0;
  transition: opacity 0.35s ease;
  pointer-events: none;
}

.card:hover {
  transform: translateY(-4px);
  border-color: rgba(56, 189, 248, 0.25);
  box-shadow: 0 24px 60px rgba(0, 0, 0, 0.35);
}

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

.tag {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent-2);
  margin-bottom: var(--space-sm);
}

.spotlight-card h3,
.course-card h3,
.app-card h3 {
  font-size: var(--step-2);
  margin: 0 0 var(--space-sm);
  letter-spacing: -0.02em;
}

.spotlight-card p,
.course-card p,
.app-card p {
  margin: 0;
  color: var(--muted);
  font-size: var(--step--1);
}

.course-head {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  margin-bottom: var(--space-sm);
}

.course-icon {
  width: 44px;
  height: 44px;
  border-radius: 14px;
  flex-shrink: 0;
  background: rgba(56, 189, 248, 0.12);
  border: 1px solid rgba(56, 189, 248, 0.2);
  position: relative;
}

.icon-opt .course-icon::after {
  content: "";
  position: absolute;
  inset: 10px;
  border-radius: 6px;
  border: 2px solid var(--accent);
  border-bottom: none;
  border-right: none;
}

.icon-speech .course-icon::after {
  content: "";
  position: absolute;
  inset: 11px 9px;
  border-radius: 12px 12px 10px 10px;
  border: 2px solid var(--accent);
}

.icon-sys .course-icon::after {
  content: "";
  position: absolute;
  inset: 11px;
  border: 2px solid var(--accent);
  border-radius: 4px;
}

.icon-ai .course-icon::after {
  content: "";
  position: absolute;
  inset: 12px;
  border-radius: 50%;
  border: 2px solid var(--accent);
}

.icon-py .course-icon::after {
  content: "";
  position: absolute;
  inset: 12px;
  border-radius: 4px;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  opacity: 0.7;
}

.app-top {
  display: flex;
  justify-content: flex-end;
  margin-bottom: var(--space-sm);
}

.app-card .btn-ghost {
  margin-top: var(--space-md);
}

.badge {
  font-size: 0.72rem;
  font-weight: 700;
  padding: 0.25rem 0.55rem;
  border-radius: 999px;
  background: rgba(52, 211, 153, 0.15);
  color: var(--success);
  border: 1px solid rgba(52, 211, 153, 0.28);
}

/* Floating section navigation */
.float-nav {
  position: fixed;
  top: 50%;
  right: 1rem;
  z-index: 90;
  transform: translateY(-50%);
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding: 10px 8px;
  border-radius: 999px;
  border: 1px solid var(--stroke);
  background: rgba(7, 10, 18, 0.72);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.35);
}

body.rtl .float-nav {
  right: auto;
  left: 1rem;
}

@media (max-width: 768px) {
  .float-nav {
    right: 6px;
    padding: 8px 6px;
    gap: 4px;
  }
  body.rtl .float-nav {
    left: 6px;
  }
}

.float-nav-btn {
  display: grid;
  place-items: center;
  width: 36px;
  height: 36px;
  border-radius: 999px;
  font-size: 0.85rem;
  line-height: 1;
  color: var(--muted);
  text-decoration: none;
  border: 1px solid transparent;
  transition: color 0.2s, background 0.2s, border-color 0.2s, transform 0.15s;
}

.float-nav-btn:hover {
  color: var(--text);
  background: rgba(56, 189, 248, 0.1);
  border-color: rgba(56, 189, 248, 0.2);
}

.float-nav-btn.active {
  color: #0f172a;
  background: linear-gradient(135deg, var(--accent), #0ea5e9);
  border-color: transparent;
  box-shadow: 0 0 16px rgba(14, 165, 233, 0.35);
}

/* Footer */
.site-footer {
  padding: var(--space-2xl) 1rem calc(var(--space-2xl) + var(--space-md));
  border-top: 1px solid var(--stroke);
}

.footer-panel {
  width: min(var(--max), 100% - 2rem);
  margin-inline: auto;
  padding: var(--space-xl) var(--space-lg);
  border-radius: var(--radius-lg);
  border: 1px solid var(--stroke);
  background: linear-gradient(165deg, rgba(15, 23, 42, 0.9), rgba(7, 10, 18, 0.65));
  text-align: center;
}

.footer-email {
  margin: 0 0 var(--space-md);
  font-size: var(--step-1);
}

.footer-email a {
  color: var(--text);
  font-weight: 600;
  text-decoration: none;
}

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

.footer-tag {
  display: inline-block;
  margin-inline-start: var(--space-sm);
  font-size: var(--step--1);
  font-weight: 700;
  color: var(--accent-2);
  opacity: 0.85;
}

.footer-copy {
  margin: var(--space-lg) 0 0;
  font-size: var(--step--1);
  color: var(--muted);
}

.section-bridge .bridge-grid {
  margin-bottom: 0;
}

/* Reveal */
.reveal {
  opacity: 0;
  transform: translateY(22px);
  transition: opacity 0.65s ease, transform 0.65s ease;
  transition-delay: calc(var(--d, 0) * 55ms);
}

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

.section-head.reveal {
  transition-delay: 0ms;
}