/* ==========================================================================
   Components - Navigation, Cards, Buttons, Footer, Forms
   ========================================================================== */

/* ==========================================================================
   Navigation
   ========================================================================== */

.nav {
  position: sticky;
  top: 0;
  z-index: var(--z-sticky);
  background-color: var(--color-background);
  border-bottom: 1px solid var(--color-border);
  transition: box-shadow var(--transition-normal);
}

.nav--scrolled {
  box-shadow: var(--shadow-md);
}

.nav__container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: var(--space-4) var(--container-padding);
}

.nav__brand {
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-bold);
  color: var(--color-text-primary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

.nav__brand:hover {
  color: var(--color-primary);
}

.nav__menu {
  display: flex;
  align-items: center;
  gap: var(--space-1);
}

.nav__link {
  display: block;
  padding: var(--space-2) var(--space-4);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--color-text-secondary);
  text-decoration: none;
  border-radius: var(--radius-md);
  transition: color var(--transition-fast), background-color var(--transition-fast);
}

.nav__link:hover {
  color: var(--color-text-primary);
  background-color: var(--color-surface);
}

.nav__link--active,
.nav__link[aria-current="page"] {
  color: var(--color-primary);
  background-color: rgba(37, 99, 235, 0.1);
}

/* Mobile Navigation Toggle */
.nav__toggle {
  display: none;
  width: 44px;
  height: 44px;
  padding: var(--space-2);
  border-radius: var(--radius-md);
  transition: background-color var(--transition-fast);
}

.nav__toggle:hover {
  background-color: var(--color-surface);
}

.nav__toggle-icon {
  position: relative;
  display: block;
  width: 24px;
  height: 2px;
  background-color: var(--color-text-primary);
  border-radius: 2px;
  transition: background-color var(--transition-fast);
}

.nav__toggle-icon::before,
.nav__toggle-icon::after {
  content: '';
  position: absolute;
  left: 0;
  width: 100%;
  height: 2px;
  background-color: var(--color-text-primary);
  border-radius: 2px;
  transition: transform var(--transition-fast);
}

.nav__toggle-icon::before {
  top: -7px;
}

.nav__toggle-icon::after {
  bottom: -7px;
}

/* Mobile menu open state */
.nav__toggle[aria-expanded="true"] .nav__toggle-icon {
  background-color: transparent;
}

.nav__toggle[aria-expanded="true"] .nav__toggle-icon::before {
  transform: translateY(7px) rotate(45deg);
}

.nav__toggle[aria-expanded="true"] .nav__toggle-icon::after {
  transform: translateY(-7px) rotate(-45deg);
}

@media (max-width: 768px) {
  .nav__toggle {
    display: flex;
    align-items: center;
    justify-content: center;
  }

  .nav__menu {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    flex-direction: column;
    gap: 0;
    padding: var(--space-4);
    background-color: var(--color-background);
    border-bottom: 1px solid var(--color-border);
    box-shadow: var(--shadow-lg);
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: opacity var(--transition-normal), transform var(--transition-normal), visibility var(--transition-normal);
  }

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

  .nav__link {
    width: 100%;
    padding: var(--space-3) var(--space-4);
    text-align: left;
  }
}

/* ==========================================================================
   Buttons
   ========================================================================== */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-6);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  line-height: 1;
  text-decoration: none;
  border-radius: var(--radius-md);
  border: 2px solid transparent;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.btn--primary {
  background-color: var(--color-primary);
  color: var(--color-text-inverse);
  border-color: var(--color-primary);
}

.btn--primary:hover {
  background-color: var(--color-primary-dark);
  border-color: var(--color-primary-dark);
  color: var(--color-text-inverse);
}

.btn--secondary {
  background-color: transparent;
  color: var(--color-primary);
  border-color: var(--color-primary);
}

.btn--secondary:hover {
  background-color: var(--color-primary);
  color: var(--color-text-inverse);
}

.btn--ghost {
  background-color: transparent;
  color: var(--color-text-primary);
  border-color: transparent;
}

.btn--ghost:hover {
  background-color: var(--color-surface);
}

.btn--lg {
  padding: var(--space-4) var(--space-8);
  font-size: var(--font-size-base);
}

.btn--sm {
  padding: var(--space-2) var(--space-4);
  font-size: var(--font-size-xs);
}

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

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

/* Button group */
.btn-group {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-4);
}

@media (max-width: 480px) {
  .btn-group--stack {
    flex-direction: column;
  }

  .btn-group--stack .btn {
    width: 100%;
  }
}

/* ==========================================================================
   Cards
   ========================================================================== */

.card {
  background-color: var(--color-surface-elevated);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: transform var(--transition-normal), box-shadow var(--transition-normal);
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.card--flat:hover {
  transform: none;
  box-shadow: none;
}

.card__image {
  aspect-ratio: 16 / 10;
  overflow: hidden;
  background-color: var(--color-surface);
}

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

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

.card__content {
  padding: var(--space-6);
}

.card__tag {
  display: inline-block;
  padding: var(--space-1) var(--space-3);
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-medium);
  color: var(--color-primary);
  background-color: rgba(37, 99, 235, 0.1);
  border-radius: var(--radius-full);
  margin-bottom: var(--space-3);
}

.card__title {
  font-size: var(--font-size-xl);
  margin-bottom: var(--space-2);
}

.card__description {
  color: var(--color-text-secondary);
  font-size: var(--font-size-sm);
  margin-bottom: var(--space-4);
}

.card__meta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-4);
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
}

/* Icon Card (for expertise section) */
.icon-card {
  text-align: center;
  padding: var(--space-8);
}

.icon-card__icon {
  width: 64px;
  height: 64px;
  margin: 0 auto var(--space-4);
  color: var(--color-primary);
}

.icon-card__title {
  font-size: var(--font-size-xl);
  margin-bottom: var(--space-3);
}

.icon-card__description {
  color: var(--color-text-secondary);
  font-size: var(--font-size-sm);
}

/* ==========================================================================
   Hero Section
   ========================================================================== */

.hero {
  padding: var(--space-24) 0;
  text-align: center;
  background: linear-gradient(180deg, var(--color-surface) 0%, var(--color-background) 100%);
}

.hero__tagline {
  display: inline-block;
  padding: var(--space-2) var(--space-4);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--color-primary);
  background-color: rgba(37, 99, 235, 0.1);
  border-radius: var(--radius-full);
  margin-bottom: var(--space-6);
}

.hero__title {
  margin-bottom: var(--space-6);
}

.hero__subtitle {
  font-size: var(--font-size-xl);
  color: var(--color-text-secondary);
  max-width: 700px;
  margin: 0 auto var(--space-8);
  line-height: var(--line-height-relaxed);
}

@media (max-width: 768px) {
  .hero {
    padding: var(--space-16) 0;
  }
}

/* ==========================================================================
   Stats
   ========================================================================== */

.stats {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: var(--space-8);
}

.stat {
  text-align: center;
  padding: var(--space-4);
}

.stat__value {
  font-size: var(--font-size-4xl);
  font-weight: var(--font-weight-bold);
  color: var(--color-primary);
  line-height: 1;
  margin-bottom: var(--space-2);
}

.stat__label {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  text-transform: uppercase;
  letter-spacing: var(--letter-spacing-wide);
}

@media (max-width: 480px) {
  .stats {
    gap: var(--space-4);
  }

  .stat__value {
    font-size: var(--font-size-3xl);
  }
}

/* ==========================================================================
   Skill Tags
   ========================================================================== */

.skill-group {
  margin-bottom: var(--space-8);
}

.skill-group__title {
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-semibold);
  margin-bottom: var(--space-4);
  color: var(--color-text-primary);
}

.skill-tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.skill-tag {
  display: inline-flex;
  align-items: center;
  padding: var(--space-2) var(--space-4);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--color-text-secondary);
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-full);
  transition: all var(--transition-fast);
  cursor: default;
}

.skill-tag:hover {
  color: var(--color-primary);
  border-color: var(--color-primary);
  background-color: rgba(37, 99, 235, 0.05);
}

.skill-tag--featured {
  color: var(--color-primary);
  background-color: rgba(37, 99, 235, 0.1);
  border-color: transparent;
}

/* ==========================================================================
   Filter Tabs
   ========================================================================== */

.filter-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin-bottom: var(--space-8);
  justify-content: center;
}

.filter-tab {
  padding: var(--space-2) var(--space-4);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--color-text-secondary);
  background-color: transparent;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-full);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.filter-tab:hover {
  color: var(--color-text-primary);
  border-color: var(--color-text-secondary);
}

.filter-tab--active {
  color: var(--color-text-inverse);
  background-color: var(--color-primary);
  border-color: var(--color-primary);
}

/* ==========================================================================
   Accordion
   ========================================================================== */

.accordion {
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

.accordion__item {
  border-bottom: 1px solid var(--color-border);
}

.accordion__item:last-child {
  border-bottom: none;
}

.accordion__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  padding: var(--space-4) var(--space-6);
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
  background-color: var(--color-surface);
  text-align: left;
  cursor: pointer;
  transition: background-color var(--transition-fast);
}

.accordion__header:hover {
  background-color: var(--color-border-light);
}

.accordion__icon {
  width: 20px;
  height: 20px;
  transition: transform var(--transition-normal);
}

.accordion__item--open .accordion__icon {
  transform: rotate(180deg);
}

.accordion__content {
  display: none;
  padding: var(--space-6);
  background-color: var(--color-background);
}

.accordion__item--open .accordion__content {
  display: block;
}

/* Publication entry within accordion */
.pub-entry {
  line-height: var(--line-height-relaxed);
  padding: var(--space-3) 0;
  padding-left: var(--space-6);
  text-indent: calc(-1 * var(--space-6));
  border-bottom: 1px solid var(--color-border-light);
}

.pub-entry:last-child {
  border-bottom: none;
}

.pub-entry a {
  color: var(--color-accent);
}

.pub-entry a:hover {
  text-decoration: underline;
}

.pub-year {
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-semibold);
  color: var(--color-primary);
  margin-top: var(--space-6);
  margin-bottom: var(--space-3);
}

.pub-year:first-child {
  margin-top: 0;
}

/* ==========================================================================
   Footer
   ========================================================================== */

.footer {
  padding: var(--space-12) 0;
  background-color: var(--color-text-primary);
  color: var(--color-text-inverse);
}

.footer__content {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-6);
  text-align: center;
}

.footer__links {
  display: flex;
  gap: var(--space-6);
}

.footer__link {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  color: rgba(255, 255, 255, 0.8);
  font-size: var(--font-size-sm);
  transition: color var(--transition-fast);
}

.footer__link:hover {
  color: var(--color-text-inverse);
}

.footer__link svg {
  width: 20px;
  height: 20px;
}

.footer__copyright {
  font-size: var(--font-size-sm);
  color: rgba(255, 255, 255, 0.6);
}

/* ==========================================================================
   Forms
   ========================================================================== */

.form {
  max-width: 600px;
  margin: 0 auto;
}

.form__group {
  margin-bottom: var(--space-6);
}

.form__row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-6);
}

@media (max-width: 480px) {
  .form__row {
    grid-template-columns: 1fr;
  }
}

.form__label {
  display: block;
  margin-bottom: var(--space-2);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--color-text-primary);
}

.form__label--required::after {
  content: ' *';
  color: var(--color-error);
}

.form__input,
.form__textarea {
  width: 100%;
  padding: var(--space-3) var(--space-4);
  font-size: var(--font-size-base);
  color: var(--color-text-primary);
  background-color: var(--color-background);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.form__input:focus,
.form__textarea:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.form__input--error,
.form__textarea--error {
  border-color: var(--color-error);
}

.form__input--error:focus,
.form__textarea--error:focus {
  box-shadow: 0 0 0 3px rgba(220, 38, 38, 0.1);
}

.form__textarea {
  min-height: 150px;
  resize: vertical;
}

.form__error {
  margin-top: var(--space-2);
  font-size: var(--font-size-sm);
  color: var(--color-error);
}

.form__hint {
  margin-top: var(--space-2);
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
}

/* reCAPTCHA container */
.form__recaptcha {
  margin-bottom: var(--space-6);
}

/* ==========================================================================
   CTA Section
   ========================================================================== */

.cta {
  text-align: center;
  padding: var(--space-16) 0;
  background-color: var(--color-surface);
  border-radius: var(--radius-xl);
}

.cta__title {
  margin-bottom: var(--space-4);
}

.cta__description {
  font-size: var(--font-size-lg);
  color: var(--color-text-secondary);
  max-width: 500px;
  margin: 0 auto var(--space-8);
}

/* ==========================================================================
   Contact Info
   ========================================================================== */

.contact-info {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
  margin-bottom: var(--space-8);
}

.contact-info__item {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-size: var(--font-size-lg);
}

.contact-info__item svg {
  width: 24px;
  height: 24px;
  color: var(--color-primary);
  flex-shrink: 0;
}

.contact-info__item a {
  color: var(--color-text-primary);
}

.contact-info__item a:hover {
  color: var(--color-primary);
}