/* ===== Google Fonts Import ===== */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&family=Montserrat:wght@400;500;600;700&display=swap');

/* ===== CSS Custom Properties (Variables) ===== */
:root {
  /* Light Theme */
  --color-bg: #ffffff;
  --color-bg-secondary: #f5f7fa;
  --color-text: #1a1a2e;
  --color-text-secondary: #555;
  --color-accent: #4a90d9;
  --color-accent-hover: #357abd;
  --color-card-bg: #ffffff;
  --color-card-shadow: rgba(0, 0, 0, 0.08);
  --color-card-shadow-hover: rgba(0, 0, 0, 0.15);
  --color-border: #e0e0e0;
  --color-filter-btn: #eef1f5;
  --color-filter-btn-active: #4a90d9;
  --color-filter-btn-text: #333;
  --color-filter-btn-active-text: #fff;
  --color-header-bg: #ffffff;
  --color-footer-bg: #1a1a2e;
  --color-footer-text: #fff;
  --color-overlay: rgba(0, 0, 0, 0.5);
  --color-input-bg: #f5f7fa;
  --color-input-border: #d0d5dd;
  --color-burger-bg: #333;

  /* Typography */
  --font-family: 'Inter', 'Montserrat', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 2rem;

  /* Spacing */
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2rem;
  --spacing-2xl: 3rem;

  /* Border Radius */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;

  /* Transitions */
  --transition-fast: 0.2s ease;
  --transition-base: 0.3s ease;
  --transition-slow: 0.4s ease;

  /* Layout */
  --container-max-width: 1200px;
  --header-height: 70px;
}

/* Dark Theme */
[data-theme="dark"] {
  --color-bg: #121212;
  --color-bg-secondary: #1e1e2e;
  --color-text: #e0e0e0;
  --color-text-secondary: #aaa;
  --color-accent: #6ab0ff;
  --color-accent-hover: #4a90d9;
  --color-card-bg: #1e1e2e;
  --color-card-shadow: rgba(0, 0, 0, 0.3);
  --color-card-shadow-hover: rgba(0, 0, 0, 0.5);
  --color-border: #333;
  --color-filter-btn: #2a2a3e;
  --color-filter-btn-active: #6ab0ff;
  --color-filter-btn-text: #ccc;
  --color-filter-btn-active-text: #121212;
  --color-header-bg: #1a1a2e;
  --color-footer-bg: #0d0d1a;
  --color-footer-text: #ccc;
  --color-input-bg: #2a2a3e;
  --color-input-border: #444;
  --color-burger-bg: #e0e0e0;
}

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

html {
  scroll-behavior: smooth;
  transition: background-color var(--transition-base);
}

body {
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  line-height: 1.6;
  color: var(--color-text);
  background-color: var(--color-bg);
  transition: background-color var(--transition-base), color var(--transition-base);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

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

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

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

ul {
  list-style: none;
}

button {
  cursor: pointer;
  border: none;
  background: none;
  font-family: inherit;
  font-size: inherit;
}

input {
  font-family: inherit;
  font-size: inherit;
}

/* ===== Utility ===== */
.container {
  max-width: var(--container-max-width);
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
}

.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;
}

/* ===== Keyframes ===== */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

@keyframes scaleIn {
  from {
    opacity: 0;
    transform: scale(0.95);
  }
  to {
    opacity: 1;
    transform: scale(1);
  }
}

/* ===== Header ===== */
.header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: var(--color-header-bg);
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.08);
  transition: background-color var(--transition-base);
  height: var(--header-height);
}

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

.header__logo {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  color: var(--color-text);
  font-size: var(--font-size-xl);
  font-weight: 700;
  text-decoration: none;
}

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

.header__logo-icon {
  font-size: var(--font-size-2xl);
}

/* Navigation */
.header__nav-list {
  display: flex;
  gap: var(--spacing-lg);
}

.header__nav-link {
  color: var(--color-text-secondary);
  font-weight: 500;
  padding: var(--spacing-sm) var(--spacing-md);
  border-radius: var(--radius-sm);
  transition: color var(--transition-fast), background-color var(--transition-fast), transform var(--transition-fast);
  position: relative;
}

.header__nav-link::after {
  content: '';
  position: absolute;
  bottom: 2px;
  left: var(--spacing-md);
  right: var(--spacing-md);
  height: 2px;
  background-color: var(--color-accent);
  transform: scaleX(0);
  transition: transform var(--transition-fast);
}

.header__nav-link:hover::after {
  transform: scaleX(1);
}

.header__nav-link:hover,
.header__nav-link:focus-visible,
.header__nav-link--active {
  color: var(--color-accent);
  background-color: var(--color-filter-btn);
}

.header__nav-link--active::after {
  transform: scaleX(1);
}

/* Theme Toggle */
.header__theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background-color: var(--color-filter-btn);
  transition: background-color var(--transition-fast), transform var(--transition-fast);
  font-size: var(--font-size-xl);
  position: relative;
  overflow: hidden;
}

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

.header__theme-toggle:hover {
  background-color: var(--color-border);
  transform: scale(1.1);
}

.header__theme-toggle:active {
  transform: scale(0.95);
}

.header__theme-icon {
  display: inline-block;
  transition: transform 0.4s ease;
}

.header__theme-toggle:hover .header__theme-icon {
  animation: themePulse 0.6s ease;
}

@keyframes themePulse {
  0% { transform: scale(1); }
  50% { transform: scale(1.3) rotate(15deg); }
  100% { transform: scale(1) rotate(0deg); }
}

/* Mobile Menu Backdrop */
.header__backdrop {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: var(--color-overlay);
  z-index: 98;
  opacity: 0;
  visibility: hidden;
  transition: opacity var(--transition-base), visibility var(--transition-base);
}

.header__backdrop--visible {
  opacity: 1;
  visibility: visible;
}

/* Burger Menu */
.header__burger {
  display: none;
  flex-direction: column;
  gap: 5px;
  padding: 8px;
  cursor: pointer;
  border-radius: var(--radius-sm);
}

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

.header__burger-line {
  display: block;
  width: 24px;
  height: 2px;
  background-color: var(--color-burger-bg);
  border-radius: 2px;
  transition: transform var(--transition-base), opacity var(--transition-base);
}

.header__burger--active .header__burger-line:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.header__burger--active .header__burger-line:nth-child(2) {
  opacity: 0;
}

.header__burger--active .header__burger-line:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* ===== Search & Filter Section ===== */
.search-filter {
  padding: var(--spacing-xl) 0 var(--spacing-lg);
}

.search-filter__search {
  margin-bottom: var(--spacing-lg);
}

.search-filter__input {
  width: 100%;
  max-width: 500px;
  padding: 12px 16px;
  border: 2px solid var(--color-input-border);
  border-radius: var(--radius-md);
  background-color: var(--color-input-bg);
  color: var(--color-text);
  font-size: var(--font-size-base);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast), background-color var(--transition-base), color var(--transition-base);
  outline: none;
}

.search-filter__input::placeholder {
  color: var(--color-text-secondary);
}

.search-filter__input:focus {
  border-color: var(--color-accent);
  box-shadow: 0 0 0 3px rgba(74, 144, 217, 0.15);
}

/* Filter Buttons (Unordered List) */
.search-filter__filters-list {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-sm);
  list-style: none;
  padding: 0;
  margin: 0;
}

.search-filter__filters-item {
  list-style: none;
}

.search-filter__btn {
  padding: 8px 18px;
  border-radius: 20px;
  background-color: var(--color-filter-btn);
  color: var(--color-filter-btn-text);
  font-weight: 500;
  font-size: var(--font-size-sm);
  transition: background-color var(--transition-fast), color var(--transition-fast), transform var(--transition-fast), box-shadow var(--transition-fast);
  white-space: nowrap;
  position: relative;
}

.search-filter__btn--active {
  background-color: var(--color-filter-btn-active);
  color: var(--color-filter-btn-active-text);
  box-shadow: 0 2px 8px rgba(74, 144, 217, 0.25);
}

.search-filter__btn--active:hover {
  box-shadow: 0 4px 16px rgba(74, 144, 217, 0.35);
}

.search-filter__btn:hover,
.search-filter__btn:focus-visible {
  transform: translateY(-2px);
  box-shadow: 0 4px 12px var(--color-card-shadow-hover);
}

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

.search-filter__btn:active {
  transform: translateY(0);
}

/* ===== Cards Grid ===== */
.cards {
  padding-bottom: var(--spacing-2xl);
}

.cards__grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--spacing-xl);
  transition: opacity var(--transition-base);
}

/* Card */
.card {
  background-color: var(--color-card-bg);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: 0 2px 8px var(--color-card-shadow);
  transition: transform var(--transition-base), box-shadow var(--transition-base), opacity var(--transition-base), background-color var(--transition-base);
  display: flex;
  flex-direction: column;
  animation: fadeInUp 0.5s ease forwards;
  position: relative;
}

/* Card leaving (filter transition) */
.card--fade-out {
  opacity: 0;
  transform: scale(0.92) translateY(10px);
  animation: none;
  pointer-events: none;
}

.card::after {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  border-radius: var(--radius-lg);
  box-shadow: 0 0 0 0 var(--color-accent);
  transition: box-shadow var(--transition-base);
  pointer-events: none;
}

.card:hover {
  transform: translateY(-8px) scale(1.02);
  box-shadow: 0 16px 40px var(--color-card-shadow-hover);
}

.card:hover::after {
  box-shadow: inset 0 0 0 2px var(--color-accent);
}

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

.card__image-wrapper {
  width: 100%;
  height: 200px;
  overflow: hidden;
}

.card__image {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform var(--transition-slow);
}

.card:hover .card__image {
  transform: scale(1.05);
}

.card__content {
  padding: var(--spacing-lg);
  display: flex;
  flex-direction: column;
  flex: 1;
  transition: background-color var(--transition-base);
}

.card__title {
  font-size: var(--font-size-xl);
  font-weight: 700;
  margin-bottom: var(--spacing-sm);
  color: var(--color-text);
  transition: color var(--transition-base);
}

.card__description {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-lg);
  flex: 1;
  line-height: 1.5;
  transition: color var(--transition-base);
}

.card__btn {
  align-self: flex-start;
  padding: 10px 24px;
  background-color: var(--color-accent);
  color: #fff;
  border-radius: var(--radius-sm);
  font-weight: 600;
  font-size: var(--font-size-sm);
  transition: background-color var(--transition-fast), transform var(--transition-fast), box-shadow var(--transition-fast);
  position: relative;
  overflow: hidden;
}

.card__btn::before {
  content: '';
  position: absolute;
  top: 0;
  left: -100%;
  width: 100%;
  height: 100%;
  background: linear-gradient(90deg, transparent, rgba(255,255,255,0.2), transparent);
  transition: left 0.6s ease;
}

.card__btn:hover,
.card__btn:focus-visible {
  background-color: var(--color-accent-hover);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(74, 144, 217, 0.3);
}

.card__btn:hover::before {
  left: 100%;
}

.card__btn:active {
  transform: translateY(0);
}

/* ===== Page Sections (About, Contacts) ===== */
.page-section {
  padding: var(--spacing-2xl) 0;
  transition: opacity var(--transition-base), visibility var(--transition-base);
}

.page-section--hidden {
  display: none;
}

.page-section__title {
  font-size: var(--font-size-3xl);
  font-weight: 700;
  margin-bottom: var(--spacing-lg);
  color: var(--color-text);
}

.page-section__text {
  font-size: var(--font-size-lg);
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-md);
  max-width: 700px;
  line-height: 1.8;
}

.page-section__link {
  color: var(--color-accent);
  font-weight: 600;
}

/* ===== Detail View ===== */
.detail-view {
  padding: var(--spacing-2xl) 0;
}

.detail-view__back-btn {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-sm);
  padding: 10px 20px;
  background-color: var(--color-filter-btn);
  color: var(--color-text);
  border-radius: var(--radius-sm);
  font-weight: 500;
  margin-bottom: var(--spacing-xl);
  transition: background-color var(--transition-fast), transform var(--transition-fast), box-shadow var(--transition-fast);
}

.detail-view__back-btn:hover,
.detail-view__back-btn:focus-visible {
  background-color: var(--color-border);
  transform: translateX(-3px);
  box-shadow: 0 2px 8px var(--color-card-shadow-hover);
}

.detail-view__back-btn:active {
  transform: translateX(0);
}

.detail-view__wrapper {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-2xl);
  align-items: start;
}

.detail-view__image-wrapper {
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: 0 4px 16px var(--color-card-shadow);
  transition: box-shadow var(--transition-base);
}

.detail-view__image {
  width: 100%;
  height: auto;
  display: block;
}

.detail-view__name {
  font-size: var(--font-size-3xl);
  font-weight: 700;
  margin-bottom: var(--spacing-xs);
  color: var(--color-text);
}

.detail-view__scientific-name {
  font-size: var(--font-size-lg);
  font-style: italic;
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-lg);
}

.detail-view__description {
  font-size: var(--font-size-base);
  color: var(--color-text-secondary);
  line-height: 1.8;
  margin-bottom: var(--spacing-xl);
}

.detail-view__characteristics {
  margin-bottom: var(--spacing-xl);
}

.detail-view__char-title {
  font-size: var(--font-size-lg);
  font-weight: 600;
  margin-bottom: var(--spacing-md);
  color: var(--color-text);
}

.detail-view__char-list {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-sm);
}

.detail-view__char-item {
  padding: var(--spacing-sm) var(--spacing-md);
  background-color: var(--color-bg-secondary);
  border-radius: var(--radius-sm);
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  transition: background-color var(--transition-base), color var(--transition-base);
}

.detail-view__char-item strong {
  color: var(--color-text);
  display: block;
  margin-bottom: 2px;
}

.detail-view__facts-title {
  font-size: var(--font-size-lg);
  font-weight: 600;
  margin-bottom: var(--spacing-md);
  color: var(--color-text);
}

.detail-view__facts-list {
  list-style: disc;
  padding-left: var(--spacing-lg);
}

.detail-view__fact-item {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-sm);
  line-height: 1.6;
}

/* ===== Footer ===== */
.footer {
  background-color: var(--color-footer-bg);
  color: var(--color-footer-text);
  padding: var(--spacing-xl) 0;
  margin-top: auto;
  transition: background-color var(--transition-base), color var(--transition-base);
}

.footer__container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--spacing-lg);
}

.footer__copyright {
  font-size: var(--font-size-sm);
  margin-bottom: var(--spacing-xs);
}

.footer__contact {
  font-size: var(--font-size-sm);
}

.footer__link {
  color: var(--color-accent);
}

.footer__link:hover {
  text-decoration: underline;
}

.footer__social {
  display: flex;
  gap: var(--spacing-md);
}

.footer__social-link {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background-color: rgba(255, 255, 255, 0.1);
  color: var(--color-footer-text);
  transition: background-color var(--transition-fast), color var(--transition-fast);
}

.footer__social-link:hover,
.footer__social-link:focus-visible {
  background-color: var(--color-accent);
  color: #fff;
}

.footer__social-icon {
  width: 20px;
  height: 20px;
}

/* ===== Responsive Design ===== */

/* Tablet: 768px - 1023px */
@media (max-width: 1023px) {
  .cards__grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .detail-view__wrapper {
    grid-template-columns: 1fr;
  }
}

/* Mobile: < 768px */
@media (max-width: 767px) {
  :root {
    --header-height: 60px;
  }

  .container {
    padding: 0 var(--spacing-md);
  }

  /* Burger Menu */
  .header__burger {
    display: flex;
  }

  .header__nav {
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    background-color: var(--color-header-bg);
    padding: var(--spacing-lg);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    transform: translateY(-100%);
    opacity: 0;
    visibility: hidden;
    transition: transform var(--transition-base), opacity var(--transition-base), visibility var(--transition-base);
    z-index: 99;
    border-bottom: 2px solid var(--color-border);
  }

  .header__nav--open {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
    animation: slideInDown 0.3s ease forwards;
  }

  @keyframes slideInDown {
    from {
      transform: translateY(-100%);
      opacity: 0;
    }
    to {
      transform: translateY(0);
      opacity: 1;
    }
  }

  .header__nav-list {
    flex-direction: column;
    gap: var(--spacing-sm);
  }

  .header__nav-link {
    display: block;
    padding: var(--spacing-md);
    font-size: var(--font-size-lg);
  }

  /* Cards */
  .cards__grid {
    grid-template-columns: 1fr;
  }

  .card__image-wrapper {
    height: 180px;
  }

  /* Search & Filter */
  .search-filter__input {
    max-width: 100%;
  }

  .search-filter__filters-list {
    gap: var(--spacing-xs);
  }

  .search-filter__btn {
    font-size: var(--font-size-xs);
    padding: 6px 14px;
  }

  /* Detail View */
  .detail-view__char-list {
    grid-template-columns: 1fr;
  }

  /* Footer */
  .footer__container {
    flex-direction: column;
    text-align: center;
  }
}

/* Desktop Large: >= 1200px */
@media (min-width: 1200px) {
  .cards__grid {
    grid-template-columns: repeat(4, 1fr);
  }
}