/* ========================================
   Science Digest 25 - Enhanced Styles
   Modern Design System & Animations
   ======================================== */

/* --- CSS Variables --- */
:root {
  --sd-primary: #0d6efd;
  --sd-primary-dark: #0b5ed7;
  --sd-secondary: #6c757d;
  --sd-accent: #20c997;
  --sd-dark: #212529;
  --sd-light: #f8f9fa;
  --sd-gradient-hero: linear-gradient(135deg, #0d6efd 0%, #6610f2 100%);
  --sd-gradient-footer: linear-gradient(180deg, #1a1d20 0%, #0d0f11 100%);
  --sd-shadow-sm: 0 0.125rem 0.5rem rgba(0, 0, 0, 0.075);
  --sd-shadow: 0 0.5rem 1.5rem rgba(0, 0, 0, 0.1);
  --sd-shadow-lg: 0 1rem 3rem rgba(0, 0, 0, 0.15);
  --sd-shadow-hover: 0 1rem 2.5rem rgba(13, 110, 253, 0.2);
  --sd-transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --sd-radius: 0.75rem;
  --sd-radius-lg: 1rem;
}

/* --- Base & Typography --- */
html {
  scroll-behavior: smooth;
  scroll-padding-top: 80px;
}

body {
  font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
  line-height: 1.7;
  color: var(--sd-dark);
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

::selection {
  background: rgba(13, 110, 253, 0.2);
  color: var(--sd-dark);
}

/* Custom Scrollbar */
::-webkit-scrollbar {
  width: 10px;
}
::-webkit-scrollbar-track {
  background: var(--sd-light);
}
::-webkit-scrollbar-thumb {
  background: linear-gradient(180deg, var(--sd-primary), #6610f2);
  border-radius: 10px;
}
::-webkit-scrollbar-thumb:hover {
  background: linear-gradient(180deg, var(--sd-primary-dark), #520dc2);
}

/* --- Animations --- */
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(40px); }
  to { opacity: 1; transform: translateY(0); }
}
@keyframes fadeInDown {
  from { opacity: 0; transform: translateY(-30px); }
  to { opacity: 1; transform: translateY(0); }
}
@keyframes fadeInLeft {
  from { opacity: 0; transform: translateX(-40px); }
  to { opacity: 1; transform: translateX(0); }
}
@keyframes fadeInRight {
  from { opacity: 0; transform: translateX(40px); }
  to { opacity: 1; transform: translateX(0); }
}
@keyframes scaleIn {
  from { opacity: 0; transform: scale(0.9); }
  to { opacity: 1; transform: scale(1); }
}
@keyframes slideIn {
  from { opacity: 0; transform: translateX(-100%); }
  to { opacity: 1; transform: translateX(0); }
}
@keyframes pulse {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.05); }
}
@keyframes float {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-10px); }
}
@keyframes shimmer {
  0% { background-position: -200% 0; }
  100% { background-position: 200% 0; }
}
@keyframes spin-slow {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}
@keyframes gradient-shift {
  0% { background-position: 0% 50%; }
  50% { background-position: 100% 50%; }
  100% { background-position: 0% 50%; }
}

/* --- Header & Navigation --- */
#header {
  position: sticky;
  top: 0;
  z-index: 1050;
  backdrop-filter: blur(12px);
  background: rgba(255, 255, 255, 0.95) !important;
  border-bottom: 1px solid rgba(0, 0, 0, 0.06);
  transition: var(--sd-transition);
  animation: fadeInDown 0.6s ease-out;
}

#header.scrolled {
  box-shadow: var(--sd-shadow);
}

.top-bar {
  background: var(--sd-gradient-hero);
  background-size: 200% 200%;
  animation: gradient-shift 6s ease infinite;
  font-size: 0.85rem;
  letter-spacing: 0.02em;
}

.top-bar a {
  color: rgba(255, 255, 255, 0.9);
  transition: var(--sd-transition);
  text-decoration: none;
}
.top-bar a:hover {
  color: #fff;
  transform: translateY(-1px);
}

.navbar {
  padding: 0.75rem 0;
  transition: var(--sd-transition);
}

.navbar-brand img {
  transition: var(--sd-transition);
}
.navbar-brand:hover img {
  transform: scale(1.03);
}

.navbar-nav .nav-link {
  font-weight: 500;
  font-size: 0.95rem;
  padding: 0.5rem 1rem !important;
  border-radius: var(--sd-radius);
  transition: var(--sd-transition);
  position: relative;
  color: #000 !important;
}
.navbar-nav .nav-link:hover {
  color: #000 !important;
  transform: translateY(-2px);
}
.navbar-light .navbar-nav .nav-link {
  color: #000 !important;
}
.navbar-light .navbar-nav .nav-link:hover {
  color: #000 !important;
}

.navbar-toggler {
  border: none;
  padding: 0.5rem;
  transition: var(--sd-transition);
}
.navbar-toggler:hover {
  transform: scale(1.1);
}
.navbar-toggler-icon {
  background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 30 30'%3e%3cpath stroke='rgba%28255, 255, 255, 0.9%29' stroke-linecap='round' stroke-miterlimit='10' stroke-width='2' d='M4 7h22M4 15h22M4 23h22'/%3e%3c/svg%3e");
}

/* --- Hero / Carousel --- */
#home-carousel {
  border-radius: 0;
  overflow: hidden;
}
#home-carousel .carousel-item {
  min-height: 500px;
  background-size: cover;
  background-position: center;
  position: relative;
}
#home-carousel .carousel-item::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(180deg, rgba(0,0,0,0.3) 0%, rgba(0,0,0,0.6) 100%);
  z-index: 1;
}
#home-carousel .carousel-caption {
  z-index: 2;
  bottom: 15%;
  text-align: left;
  max-width: 700px;
}
#home-carousel .carousel-caption h1 {
  font-size: 3rem;
  font-weight: 800;
  text-shadow: 0 2px 20px rgba(0,0,0,0.3);
  animation: fadeInUp 0.8s ease-out;
}
#home-carousel .carousel-caption p {
  font-size: 1.1rem;
  text-shadow: 0 1px 10px rgba(0,0,0,0.3);
  animation: fadeInUp 1s ease-out 0.2s both;
}
#home-carousel .carousel-caption .btn {
  animation: fadeInUp 1s ease-out 0.4s both;
}
.carousel-control-prev,
.carousel-control-next {
  width: 60px;
  height: 60px;
  background: rgba(255,255,255,0.15);
  backdrop-filter: blur(8px);
  border-radius: 50%;
  top: 50%;
  transform: translateY(-50%);
  margin: 0 1.5rem;
  opacity: 0;
  transition: var(--sd-transition);
}
#home-carousel:hover .carousel-control-prev,
#home-carousel:hover .carousel-control-next {
  opacity: 1;
}
.carousel-control-prev:hover,
.carousel-control-next:hover {
  background: rgba(255,255,255,0.3);
  transform: translateY(-50%) scale(1.1);
}
.carousel-indicators {
  bottom: 30px;
}
.carousel-indicators button {
  width: 12px;
  height: 12px;
  border-radius: 50%;
  margin: 0 6px;
  transition: var(--sd-transition);
  background: rgba(255,255,255,0.5);
}
.carousel-indicators button.active {
  background: #fff;
  transform: scale(1.3);
}

/* --- Sections --- */
.section {
  position: relative;
  overflow: hidden;
}
.section-header {
  margin-bottom: 2.5rem;
}
.section-header h2 {
  font-weight: 700;
  position: relative;
  display: inline-block;
}
.section-header h2::after {
  content: '';
  position: absolute;
  bottom: -8px;
  left: 0;
  width: 60px;
  height: 4px;
  background: var(--sd-gradient-hero);
  border-radius: 2px;
  transition: var(--sd-transition);
}
.section-header:hover h2::after {
  width: 100%;
}

/* --- Cards & Thumbnails --- */
.article-thumbnail {
  background: #fff;
  border-radius: var(--sd-radius);
  overflow: hidden;
  transition: var(--sd-transition);
  border: 1px solid rgba(0,0,0,0.04);
  position: relative;
}
.article-thumbnail:hover {
  transform: translateY(-6px);
  box-shadow: var(--sd-shadow-hover);
  border-color: rgba(13, 110, 253, 0.15);
}
.article-thumbnail img {
  transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
}
.article-thumbnail:hover img {
  transform: scale(1.05);
}
.article-thumbnail .article-content {
  padding: 1.25rem;
}
.article-thumbnail .article-title a {
  color: var(--sd-dark);
  text-decoration: none;
  font-weight: 600;
  transition: var(--sd-transition);
  line-height: 1.4;
}
.article-thumbnail .article-title a:hover {
  color: var(--sd-primary);
}
.article-category {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--sd-primary);
  font-weight: 600;
  margin-bottom: 0.35rem;
}

/* --- Cards (Service cards, etc.) --- */
.card {
  border: none;
  border-radius: var(--sd-radius-lg);
  overflow: hidden;
  transition: var(--sd-transition);
  box-shadow: var(--sd-shadow-sm);
}
.card:hover {
  transform: translateY(-8px);
  box-shadow: var(--sd-shadow-lg);
}
.card-img-top {
  transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
}
.card:hover .card-img-top {
  transform: scale(1.06);
}
.card-body {
  padding: 1.5rem;
}
.card-title {
  font-weight: 700;
  font-size: 1.1rem;
}
.card-text {
  color: var(--sd-secondary);
  font-size: 0.95rem;
  line-height: 1.6;
}

/* --- Buttons --- */
.btn {
  font-weight: 600;
  letter-spacing: 0.02em;
  transition: var(--sd-transition);
  border-radius: var(--sd-radius);
  position: relative;
  overflow: hidden;
}
.btn::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, rgba(255,255,255,0.2) 0%, transparent 100%);
  opacity: 0;
  transition: var(--sd-transition);
}
.btn:hover::before {
  opacity: 1;
}
.btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 0.5rem 1.5rem rgba(13, 110, 253, 0.3);
}
.btn-primary {
  background: var(--sd-gradient-hero);
  border: none;
}
.btn-primary:hover {
  background: linear-gradient(135deg, #0b5ed7 0%, #520dc2 100%);
}
.btn-outline-primary {
  border-width: 2px;
}
.btn-outline-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 0.5rem 1.5rem rgba(13, 110, 253, 0.25);
}
.btn-lg {
  padding: 0.75rem 2rem;
  font-size: 1.05rem;
}
.btn-rounded {
  border-radius: 50px !important;
}

/* --- Forms --- */
.form-control {
  border-radius: var(--sd-radius);
  border: 2px solid #e9ecef;
  padding: 0.75rem 1rem;
  font-size: 0.95rem;
  transition: var(--sd-transition);
  background: #fafbfc;
}
.form-control:focus {
  border-color: var(--sd-primary);
  box-shadow: 0 0 0 0.25rem rgba(13, 110, 253, 0.1);
  background: #fff;
  transform: translateY(-1px);
}
.form-control.rounded-0 {
  border-radius: 0 !important;
}
.form-label {
  font-weight: 600;
  font-size: 0.9rem;
  margin-bottom: 0.5rem;
  color: var(--sd-dark);
}
.input-group-text {
  border: 2px solid #e9ecef;
  border-right: none;
  background: #fafbfc;
  color: var(--sd-secondary);
}
.input-group .form-control {
  border-left: none;
}
.input-group:focus-within .input-group-text {
  border-color: var(--sd-primary);
  color: var(--sd-primary);
}
.input-group:focus-within .form-control {
  border-color: var(--sd-primary);
}

/* --- Alerts --- */
.alert {
  border: none;
  border-radius: var(--sd-radius);
  font-weight: 500;
  animation: fadeInUp 0.4s ease-out;
  box-shadow: var(--sd-shadow-sm);
}
.alert-success {
  background: #d1e7dd;
  color: #0f5132;
}
.alert-danger {
  background: #f8d7da;
  color: #842029;
}
.alert-warning {
  background: #fff3cd;
  color: #664d03;
}
.alert-info {
  background: #d1ecf1;
  color: #055160;
}

/* --- Badges --- */
.badge {
  font-weight: 600;
  letter-spacing: 0.03em;
  padding: 0.4em 0.8em;
  border-radius: 50px;
  animation: scaleIn 0.3s ease-out;
}

/* --- Footer --- */
#footer {
  background: var(--sd-gradient-footer);
  color: rgba(255, 255, 255, 0.8);
  position: relative;
  overflow: hidden;
}
#footer::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: var(--sd-gradient-hero);
  background-size: 200% 200%;
  animation: gradient-shift 4s ease infinite;
}
.footer-title {
  color: #fff;
  font-weight: 700;
  font-size: 1.1rem;
  margin-bottom: 1.25rem;
  position: relative;
  padding-bottom: 0.75rem;
}
.footer-title::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 40px;
  height: 3px;
  background: var(--sd-primary);
  border-radius: 2px;
  transition: var(--sd-transition);
}
#footer a {
  color: rgba(255, 255, 255, 0.7);
  text-decoration: none;
  transition: var(--sd-transition);
}
#footer a:hover {
  color: #fff;
  padding-left: 4px;
}
.social-icons .icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: rgba(255,255,255,0.1);
  color: #fff;
  transition: var(--sd-transition);
  text-decoration: none;
  margin-right: 0.5rem;
}
.social-icons .icon:hover {
  background: var(--sd-primary);
  transform: translateY(-3px) rotate(360deg);
  box-shadow: 0 0.5rem 1rem rgba(13, 110, 253, 0.4);
}
.copyright {
  font-size: 0.85rem;
  color: rgba(255,255,255,0.5);
  padding: 1rem 0;
}

/* --- Trending Section --- */
.trending-section {
  border-radius: var(--sd-radius);
  overflow: hidden;
  box-shadow: var(--sd-shadow);
  transition: var(--sd-transition);
}
.trending-section:hover {
  box-shadow: var(--sd-shadow-lg);
}
.trending-section .content {
  max-height: 500px;
  overflow-y: auto;
}
.trending-section .thumbnails .article-thumbnail {
  border: none;
  border-bottom: 1px solid #f1f3f5;
  border-radius: 0;
}
.trending-section .thumbnails .article-thumbnail:last-child {
  border-bottom: none;
}
.trending-section .thumbnails .article-thumbnail:hover {
  background: #f8f9fa;
  transform: none;
  box-shadow: none;
}
.trending-section .footer {
  border-top: 1px solid #f1f3f5;
  padding: 0.75rem;
  background: #fafbfc;
}

/* --- Category Cards --- */
.bg-light {
  background: linear-gradient(180deg, #f8f9fa 0%, #f1f3f5 100%) !important;
  border-radius: var(--sd-radius-lg);
  transition: var(--sd-transition);
}
.bg-light:hover {
  box-shadow: var(--sd-shadow);
}
.line-divider {
  position: relative;
  height: 4px;
  background: #e9ecef;
  border-radius: 2px;
  overflow: hidden;
  margin: 1rem 0;
}
.line-divider .line span {
  display: block;
  height: 100%;
  width: 0;
  background: var(--sd-gradient-hero);
  border-radius: 2px;
  transition: width 0.8s cubic-bezier(0.4, 0, 0.2, 1);
}
.bg-light:hover .line-divider .line span {
  width: 100%;
}

/* --- Featured Video --- */
.featured-video {
  border-radius: var(--sd-radius-lg);
  overflow: hidden;
  box-shadow: var(--sd-shadow);
  transition: var(--sd-transition);
  position: relative;
}
.featured-video:hover {
  transform: translateY(-4px);
  box-shadow: var(--sd-shadow-lg);
}
.featured-video iframe,
.featured-video video {
  border-radius: var(--sd-radius-lg);
}

/* --- Contact Page --- */
.contact-info .item {
  transition: var(--sd-transition);
  border-left: 3px solid transparent;
}
.contact-info .item:hover {
  border-left-color: var(--sd-primary);
  background: #fff;
  transform: translateX(4px);
}
.contact-form {
  background: #fff;
  border-radius: var(--sd-radius-lg);
  box-shadow: var(--sd-shadow-sm);
  border: 1px solid rgba(0,0,0,0.04);
}
.contact-form .form-control {
  background: #fafbfc;
}

/* --- Search --- */
#search-form .form-control {
  border-radius: 50px 0 0 50px;
  border: 2px solid #e9ecef;
  border-right: none;
  padding: 0.6rem 1.25rem;
  transition: var(--sd-transition);
}
#search-form .form-control:focus {
  border-color: var(--sd-primary);
  box-shadow: none;
}
#search-form .btn {
  border-radius: 0 50px 50px 0;
  border: 2px solid var(--sd-primary);
  padding: 0.6rem 1.25rem;
  transition: var(--sd-transition);
}
#search-form .btn:hover {
  background: var(--sd-primary);
}

/* --- Misc UI Elements --- */
.border-bottom {
  border-bottom: 1px solid rgba(0,0,0,0.06) !important;
}
.shadow-bottom {
  box-shadow: 0 4px 20px rgba(0,0,0,0.08);
}

/* --- Page Headers --- */
.page-header {
  padding-bottom: 1rem;
  margin-bottom: 2rem;
  border-bottom: 2px solid #f1f3f5;
}
.page-header h2 {
  font-weight: 700;
  position: relative;
  display: inline-block;
}

/* --- Loading States --- */
.loading {
  position: relative;
  pointer-events: none;
  opacity: 0.7;
}
.loading::after {
  content: '';
  position: absolute;
  inset: 0;
  background: rgba(255,255,255,0.8);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 10;
}
.loading::before {
  content: '';
  position: absolute;
  top: 50%;
  left: 50%;
  width: 40px;
  height: 40px;
  margin: -20px 0 0 -20px;
  border: 3px solid #e9ecef;
  border-top-color: var(--sd-primary);
  border-radius: 50%;
  animation: spin-slow 0.8s linear infinite;
  z-index: 11;
}

/* --- Back to Top --- */
#back-to-top {
  position: fixed;
  bottom: 30px;
  right: 30px;
  width: 48px;
  height: 48px;
  background: var(--sd-gradient-hero);
  color: #fff;
  border: none;
  border-radius: 50%;
  font-size: 1.2rem;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translateY(20px);
  transition: var(--sd-transition);
  z-index: 999;
  box-shadow: var(--sd-shadow);
  display: flex;
  align-items: center;
  justify-content: center;
}
#back-to-top.visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}
#back-to-top:hover {
  transform: translateY(-4px);
  box-shadow: var(--sd-shadow-hover);
}

/* --- Responsive --- */
@media (max-width: 767px) {
  #home-carousel .carousel-item {
    min-height: 350px;
  }
  #home-carousel .carousel-caption h1 {
    font-size: 1.75rem;
  }
  #home-carousel .carousel-caption p {
    font-size: 0.95rem;
  }
  .carousel-control-prev,
  .carousel-control-next {
    display: none;
  }
  .navbar-nav .nav-link {
    padding: 0.75rem 1rem !important;
    border-radius: 0;
  }
  .navbar-nav .nav-link::after {
    display: none;
  }
  #back-to-top {
    bottom: 20px;
    right: 20px;
    width: 40px;
    height: 40px;
  }
}

@media (min-width: 768px) and (max-width: 991px) {
  #home-carousel .carousel-item {
    min-height: 400px;
  }
}

/* --- Print Styles --- */
@media print {
  #header, #footer, #back-to-top, .carousel-control-prev, .carousel-control-next {
    display: none !important;
  }
  body {
    font-size: 12pt;
    color: #000;
  }
}

/* --- Utility Classes --- */
.hover-lift {
  transition: var(--sd-transition);
}
.hover-lift:hover {
  transform: translateY(-6px);
  box-shadow: var(--sd-shadow-lg);
}

.transition-colors {
  transition: color 0.3s ease, background-color 0.3s ease, border-color 0.3s ease;
}

.transition-transform {
  transition: transform 0.3s ease;
}

.ratio-custom-16x9 {
  position: relative;
  width: 100%;
  padding-bottom: 56.25%;
}
.ratio-custom-16x9 > * {
  position: absolute;
  inset: 0;
}

.hover\:text-primary:hover {
  color: var(--sd-primary) !important;
}

.hover\:scale-105:hover {
  transform: scale(1.05);
}

.duration-500 {
  transition-duration: 500ms;
}

.gap-2 { gap: 0.5rem; }
.gap-3 { gap: 1rem; }
.gap-4 { gap: 1.5rem; }