/* ── Smooth Scrolling & Micro-interactions ─────────────
   Adds polished transitions, scroll behavior, fade-in
   animations, loading skeletons, and hover effects.
   ────────────────────────────────────────────────────── */

/* ---- Smooth scroll ---- */
html {
  scroll-behavior: smooth;
}

/* ---- Fade-in on scroll (JS adds .fade-in-visible) ---- */
.fade-in {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s cubic-bezier(0.22, 1, 0.36, 1),
              transform 0.6s cubic-bezier(0.22, 1, 0.36, 1);
}
.fade-in.fade-in-visible {
  opacity: 1;
  transform: translateY(0);
}

/* Stagger children (apply .fade-in-stagger to parent) */
.fade-in-stagger > .fade-in:nth-child(1) { transition-delay: 0s; }
.fade-in-stagger > .fade-in:nth-child(2) { transition-delay: 0.06s; }
.fade-in-stagger > .fade-in:nth-child(3) { transition-delay: 0.12s; }
.fade-in-stagger > .fade-in:nth-child(4) { transition-delay: 0.18s; }
.fade-in-stagger > .fade-in:nth-child(5) { transition-delay: 0.24s; }
.fade-in-stagger > .fade-in:nth-child(6) { transition-delay: 0.30s; }
.fade-in-stagger > .fade-in:nth-child(7) { transition-delay: 0.36s; }
.fade-in-stagger > .fade-in:nth-child(8) { transition-delay: 0.42s; }
.fade-in-stagger > .fade-in:nth-child(n+9) { transition-delay: 0.48s; }

/* ---- Interactive element transitions ---- */
a,
button,
.subject-card,
.project-card,
.testimonial-card,
.hub-tl-card,
input,
select,
textarea {
  transition: transform 0.2s cubic-bezier(0.22, 1, 0.36, 1),
              box-shadow 0.2s ease,
              background-color 0.2s ease,
              border-color 0.2s ease,
              color 0.15s ease,
              opacity 0.2s ease;
}

/* ---- Polished hover transforms ---- */
.subject-card:hover,
.project-card:hover,
.testimonial-card:hover,
.hub-tl-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 28px rgba(0, 0, 0, 0.12);
}
body.dark-mode .subject-card:hover,
body.dark-mode .project-card:hover,
body.dark-mode .testimonial-card:hover,
body.dark-mode .hub-tl-card:hover {
  box-shadow: 0 8px 28px rgba(0, 0, 0, 0.35);
}

/* Buttons — subtle press */
button:active:not(:disabled),
.subject-card:active {
  transform: scale(0.97);
}

/* Focus-visible ring */
button:focus-visible,
a:focus-visible,
input:focus-visible,
select:focus-visible,
textarea:focus-visible {
  outline: 2px solid var(--primary, #4361ee);
  outline-offset: 2px;
}

/* ---- Scroll-to-top button ---- */
.scroll-top-btn {
  position: fixed;
  bottom: 24px;
  left: 24px;
  z-index: 800;
  width: 42px;
  height: 42px;
  border-radius: 50%;
  background: var(--card, #fff);
  color: var(--text, #2b2d42);
  border: 1.5px solid var(--border, #e0e0e0);
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.1);
  font-size: 1.2rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  pointer-events: none;
  transform: translateY(12px);
  transition: opacity 0.3s ease, transform 0.3s ease, background 0.2s ease;
}
.scroll-top-btn.visible {
  opacity: 1;
  pointer-events: auto;
  transform: translateY(0);
}
.scroll-top-btn:hover {
  background: var(--primary, #4361ee);
  color: #fff;
  border-color: var(--primary, #4361ee);
  box-shadow: 0 4px 20px rgba(67, 97, 238, 0.35);
}
body.dark-mode .scroll-top-btn {
  background: var(--card, #16213e);
  border-color: rgba(255, 255, 255, 0.1);
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.3);
}
body.dark-mode .scroll-top-btn:hover {
  background: var(--primary, #4361ee);
  color: #fff;
}

/* ---- Loading skeleton ---- */
.skeleton {
  position: relative;
  overflow: hidden;
  background: var(--border-light, #f0f0f0);
  border-radius: 8px;
  color: transparent !important;
}
.skeleton * {
  visibility: hidden;
}
.skeleton::after {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(
    90deg,
    transparent 0%,
    rgba(255, 255, 255, 0.4) 50%,
    transparent 100%
  );
  animation: skeletonShimmer 1.5s ease-in-out infinite;
}
body.dark-mode .skeleton {
  background: rgba(255, 255, 255, 0.06);
}
body.dark-mode .skeleton::after {
  background: linear-gradient(
    90deg,
    transparent 0%,
    rgba(255, 255, 255, 0.08) 50%,
    transparent 100%
  );
}
@keyframes skeletonShimmer {
  0% { transform: translateX(-100%); }
  100% { transform: translateX(100%); }
}

/* ---- Page transition (fade between views) ---- */
.page-transition {
  animation: pageFadeIn 0.4s cubic-bezier(0.22, 1, 0.36, 1) forwards;
}
@keyframes pageFadeIn {
  from {
    opacity: 0;
    transform: translateY(12px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ---- Scroll-snap sections (opt-in: add .snap-container to parent) ---- */
.snap-container {
  scroll-snap-type: y proximity;
}
.snap-container > section,
.snap-container > .snap-section {
  scroll-snap-align: start;
}

/* ---- Reduced motion ---- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .fade-in { transition: none; opacity: 1; transform: none; }
  .skeleton::after { animation: none; }
  .page-transition { animation: none; opacity: 1; transform: none; }
  a, button, .subject-card, .project-card, .testimonial-card, .hub-tl-card,
  input, select, textarea {
    transition: none;
  }
  .scroll-top-btn { transition: opacity 0.15s ease; }
}