/* ==========================================================================
   CSS Variables & Custom Properties
   ========================================================================== */
:root {
  /* Typography */
  --font-family: "Inter", sans-serif;
  --font-size-xs: 0.9rem;
  --font-size-sm: 1.1rem;
  --font-size-base: 1.3rem;
  --font-size-lg: 1.4rem;
  --font-size-xl: 1.5rem;
  --font-size-2xl: 1.6rem;
  --font-size-3xl: 2rem;
  --font-size-4xl: 2.5rem;
  
  /* Font Weights */
  --font-weight-light: 300;
  --font-weight-normal: 400;
  --font-weight-medium: 500;
  
  /* Colors */
  --color-white: #fcfcff;
  --color-cream: #fff7ec;
  --color-orange-light: #fed59b;
  --color-dark: #001524;
  --color-primary: #ffb236;
  --color-secondary: #ff7d00;
  --color-heading: #15616d;
  --color-category: #5e5f6c;
  --color-text: #7d7d7d;
  --color-accent: #f99136;
  
  /* Spacing */
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2rem;
  --spacing-xl: 3rem;
  --spacing-2xl: 5rem;
  --spacing-3xl: 10rem;
  
  /* Layout */
  --navbar-height: 3.5rem;
  --container-width: 95vw;
  --sidebar-width: 30%;
  --border-radius-sm: 5px;
  --border-radius-md: 8px;
  --border-radius-lg: 10px;
  --border-radius-xl: 1em;
  
  /* Shadows */
  --shadow-sm: 0 4px 8px rgba(0, 0, 0, 0.1);
  --shadow-md: 0 8px 16px rgba(0, 0, 0, 0.2);
  
  /* Transitions */
  --transition-fast: 0.1s ease-in;
  --transition-normal: 0.3s ease;
  --transition-slow: 0.4s ease;
  --transition-slower: 0.5s ease;
  
  /* Z-index */
  --z-navbar: 10;
  --z-sidebar: 5;
  --z-menu: 9;
  --z-hamburger: 11;
}

/* ==========================================================================
   CSS Reset & Base Styles
   ========================================================================== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-family);
  background-color: var(--color-cream);
  display: flex;
  justify-content: center;
  padding: var(--spacing-lg);
  line-height: 1.6;
}

/* ==========================================================================
   Typography
   ========================================================================== */
h1, h2, h3, h4, h5, h6 {
  color: var(--color-heading);
  font-weight: var(--font-weight-medium);
  line-height: 1.3;
}

h1 { font-size: var(--font-size-4xl); margin-bottom: var(--spacing-md); }
h2 { font-size: var(--font-size-3xl); }
h3 { font-size: var(--font-size-2xl); margin-bottom: var(--spacing-sm); }
h4 { font-size: var(--font-size-lg); margin-bottom: var(--spacing-xs); }

p {
  color: var(--color-text);
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-light);
  margin-bottom: var(--spacing-sm);
  text-align: justify;
}

a {
  color: var(--color-primary);
  text-decoration: none;
  font-weight: var(--font-weight-normal);
  transition: color var(--transition-fast);
}

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

/* ==========================================================================
   Layout Components
   ========================================================================== */
.container {
  width: var(--container-width);
  display: flex;
  align-items: start;
  justify-content: space-between;
  background: var(--color-white);
  box-shadow: var(--shadow-sm);
  border-radius: var(--border-radius-md);
}

.main-content {
  flex-direction: column;
  width: 100%;
  margin: var(--spacing-sm) var(--spacing-lg);
}

/* ==========================================================================
   Navigation Bar
   ========================================================================== */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  height: var(--navbar-height);
  width: 100%;
  background-color: var(--color-dark);
  z-index: var(--z-navbar);
}

.nav-list {
  list-style: none;
  display: flex;
  justify-content: flex-end;
  align-items: center;
  padding: var(--spacing-sm) var(--spacing-3xl) var(--spacing-sm) 0;
  height: 100%;
}

.nav-list__item {
  margin: 0 var(--spacing-lg);
  text-align: center;
}

.nav-list__link {
  color: var(--color-white);
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-light);
  transition: color var(--transition-normal);
}

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

/* Hamburger Menu */
.menu-icon {
  display: none;
  flex-direction: column;
  cursor: pointer;
  width: 30px;
  z-index: var(--z-hamburger);
}

.menu-icon__line {
  height: 3px;
  background-color: var(--color-white);
  margin: 5px 0;
  transition: var(--transition-slow);
}

/* ==========================================================================
   Sidebar
   ========================================================================== */
.sidebar-back-rect {
  width: var(--sidebar-width);
  height: 100%;
  align-self: flex-start;
  background-color: var(--color-dark);
  z-index: var(--z-sidebar);
}

.sidebar {
  max-width: 400px;
  width: 100%;
  height: auto;
  background-color: var(--color-dark);
  color: var(--color-white);
  display: flex;
  align-items: center;
  text-align: center;
  flex-direction: column;
  padding: var(--spacing-xl) var(--spacing-lg);
  position: sticky;
  top: var(--spacing-xl);
  z-index: var(--z-sidebar);
}

.sidebar__image {
  width: 100%;
  max-width: 220px;
  height: 100%;
  max-height: 220px;
  border-radius: 50%;
  margin-bottom: var(--spacing-lg);
  border: 0.5vh solid var(--color-white);
  object-fit: cover;
}

.sidebar__title {
  font-size: 1.5em;
  margin-bottom: var(--spacing-sm);
  color: var(--color-white);
}

.sidebar__text {
  color: var(--color-white);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-normal);
  margin-bottom: var(--spacing-sm);
  text-align: center;
}

.social-links__link {
  font-size: var(--font-size-lg);
  text-decoration: none;
  color: var(--color-white);
  margin: 0 var(--spacing-xs);
  margin-top: var(--spacing-lg);
  transition: color var(--transition-normal);
}

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

/* ==========================================================================
   Content Sections
   ========================================================================== */
.content {
  margin-top: var(--spacing-2xl);
  margin-bottom: var(--spacing-3xl);
  padding-top: var(--spacing-3xl);
  transform: translateY(4rem);
  opacity: 0;
  transition: var(--spacing-sm) ease;
}

.content--visible-up,
.content--visible-down {
  opacity: 1;
  transform: translateY(0);
}

.content--hidden-up {
  opacity: 0;
  transform: translateY(-2rem);
}

.content--hidden-down {
  opacity: 0;
  transform: translateY(2rem);
}

/* About Section */
.about {
  padding-top: var(--spacing-2xl);
  margin-bottom: var(--spacing-3xl);
}

.about__title {
  font-weight: var(--font-weight-normal);
  text-align: center;
  padding-top: var(--spacing-sm);
}

.about__subtitle {
  font-weight: 350;
  text-align: center;
}

/* Remove unused about__text class */

.about__research-list {
  list-style-type: disc;
  padding-left: 10%;
  padding-right: 5%;
  width: 90%;
  font-size: var(--font-size-sm);
}

.about__research-item {
  margin-bottom: var(--spacing-xs);
  font-weight: var(--font-weight-light);
  color: var(--color-heading);
}

/* ==========================================================================
   Cards & Content Blocks
   ========================================================================== */
.card {
  display: flex;
  background-color: var(--color-cream);
  padding: var(--spacing-sm);
  border-radius: var(--border-radius-xl);
  margin: 0 auto var(--spacing-md);
  box-shadow: var(--shadow-sm);
  gap: var(--spacing-lg);
  align-items: center;
  width: 90%;
}

.card__image {
  flex: 0 0 100%;
  max-width: 300px;
  max-height: 300px;
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
}

.card__image img,
.card__image video {
  width: 100%;
  height: 100%;
  max-width: 100%;
  max-height: 100%;
  border-radius: var(--border-radius-xl);
  object-fit: contain;
  object-position: center;
}

.card__content {
  flex: 1;
  margin-left: var(--spacing-sm);
}

.card__title {
  font-size: var(--font-size-xl);
  margin-bottom: var(--spacing-xs);
}

.card__subtitle {
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-normal);
  color: var(--color-category);
  margin-bottom: var(--spacing-xs);
}

.card__text {
  width: 90%;
  font-size: var(--font-size-sm);
}

.card__button {
  display: inline-block;
  cursor: pointer;
  color: var(--color-white);
  background-color: var(--color-primary);
  text-decoration: none;
  text-align: center;
  font-size: 90%;
  padding: 10px 20px;
  border: none;
  border-radius: var(--border-radius-sm);
  margin: 0.5vh 0.3vh;
  transition: background-color var(--transition-normal), transform var(--transition-normal);
}

.card__button:hover {
  color: var(--color-white);
  background-color: var(--color-secondary);
  transform: scale(1.05);
}

/* ==========================================================================
   Experience & Publications
   ========================================================================== */
.experience-item {
  position: relative;
  margin-left: var(--spacing-xl);
  padding-bottom: var(--spacing-lg);
}

.experience-item:not(:last-child) {
  margin-bottom: var(--spacing-sm);
}

.experience-item::before {
  content: "";
  position: absolute;
  top: 15px;
  left: -28px;
  width: 1px;
  height: 80%;
  background-color: var(--color-dark);
}

.experience-item:not(:last-child)::before {
  height: calc(80% + 30px);
}

.experience-circle {
  position: absolute;
  top: 5px;
  left: -33px;
  width: 10px;
  height: 10px;
  background-color: var(--color-dark);
  border-radius: 50%;
  box-shadow: 0 0 0 4px #d6d6d6;
}

.experience-title,
.publication-title {
  color: var(--color-heading);
  font-size: 1.3rem;
  font-weight: var(--font-weight-medium);
  line-height: 1.3;
  margin-bottom: var(--spacing-xs);
}

.experience-category {
  font-size: 85%;
  color: var(--color-category);
  margin-bottom: var(--spacing-xs);
  margin-left: var(--spacing-sm);
}

.experience-duration {
  color: var(--color-accent);
  font-weight: var(--font-weight-normal);
  line-height: 1.6;
  margin-bottom: var(--spacing-xs);
  margin-left: var(--spacing-sm);
}

.experience-description {
  font-size: var(--font-size-sm);
  width: 90%;
  font-weight: var(--font-weight-light);
  color: var(--color-text);
  margin-left: var(--spacing-sm);
  line-height: 1.6;
  text-align: justify;
}

.experience-description ul {
  list-style-type: disc;
  padding-left: var(--spacing-sm);
  margin-top: var(--spacing-sm);
}

.experience-description li {
  margin-bottom: 5px;
  margin-left: var(--spacing-sm);
}

.publication-authors {
  font-size: var(--font-size-sm);
  width: 90%;
  font-weight: var(--font-weight-light);
  color: var(--color-text);
  margin-bottom: var(--spacing-xs);
  margin-left: var(--spacing-sm);
  line-height: 1.4;
}

.publication-date,
.publication-conference {
  font-size: 100%;
  font-weight: var(--font-weight-normal);
  color: var(--color-text);
  margin-bottom: var(--spacing-xs);
  margin-left: var(--spacing-sm);
  line-height: 1.4;
  font-style: italic;
}

.publication-button {
  color: var(--color-primary);
  font-size: 90%;
  text-decoration: none;
  background-color: var(--color-white);
  padding: 0.5rem 0.8rem;
  margin: 0.5vh 0.1vh;
  border: 2px solid var(--color-primary);
  border-radius: var(--border-radius-sm);
  display: inline-block;
  text-align: center;
  cursor: pointer;
  transition: background-color var(--transition-normal), transform var(--transition-normal);
}

.publication-button:hover {
  color: var(--color-white);
  background-color: var(--color-primary);
}

/* ==========================================================================
   Link Cards
   ========================================================================== */
.link-card-container {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: var(--spacing-lg);
  margin: 0 auto;
  max-width: 1000px;
}

.link-card {
  display: flex;
  width: calc(50% - var(--spacing-lg));
  min-height: 300px;
  background-color: var(--color-cream);
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: var(--spacing-lg);
  border-radius: var(--border-radius-lg);
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition-normal), box-shadow var(--transition-normal), background-color var(--transition-normal);
}

.link-card:hover {
  transform: scale(1.05);
  box-shadow: var(--shadow-md);
  background-color: var(--color-orange-light);
}

.video-container {
  position: relative;
  width: 100%;
  max-width: 350px;
}

.thumbnail {
  width: 100%;
  border-radius: var(--border-radius-lg);
  transition: transform var(--transition-normal), box-shadow var(--transition-normal), opacity var(--transition-normal);
}

.link-card:hover .thumbnail {
  transform: scale(1.1);
  box-shadow: var(--shadow-md);
  opacity: 1;
}

/* ==========================================================================
   Email Section
   ========================================================================== */
.email-section {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
}

.email-arrow {
  font-size: 4rem;
  color: var(--color-primary);
}

/* ==========================================================================
   Lazy Loading States
   ========================================================================== */
.project-image {
  opacity: 0;
  filter: blur(3px);
  transition: opacity var(--transition-slow) ease-in-out, filter var(--transition-slow) ease-in-out;
  width: 100%;
  height: 100%;
  object-fit: contain;
  object-position: center;
}

.project-image-loaded,
.achievement-image-loaded {
  opacity: 1;
  filter: blur(0);
  width: 100%;
  height: 100%;
  object-fit: contain;
  object-position: center;
}

.card-image::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: linear-gradient(90deg, #f0f0f0 25%, #e0e0e0 50%, #f0f0f0 75%);
  background-size: 200% 100%;
  animation: loading 1.5s infinite;
  z-index: -1;
}

@keyframes loading {
  0% { background-position: 200% 0; }
  100% { background-position: -200% 0; }
}

/* ==========================================================================
   Responsive Design - Mobile First
   ========================================================================== */

/* Small devices (landscape phones, 576px and up) */
@media (min-width: 576px) {
  .container {
    width: 95%;
  }
}

/* Medium devices (tablets, 768px and up) */
@media (min-width: 768px) {
  .container {
    width: 95%;
  }
  
  .sidebar {
    max-width: 400px;
  }
  
  .card {
    gap: var(--spacing-md);
  }
  
  .link-card {
    width: calc(50% - var(--spacing-md));
  }
}

/* Large devices (desktops, 992px and up) */
@media (min-width: 992px) {
  .container {
    width: var(--container-width);
  }
}

/* Extra large devices (large desktops, 1200px and up) */
@media (min-width: 1200px) {
  .container {
    width: 90%;
  }
}

/* Mobile-specific adjustments */
@media (max-width: 767px) {
  body {
    padding: var(--spacing-sm);
  }
  
  .container {
    width: 95%;
    flex-direction: column;
    margin: var(--spacing-xl) auto;
  }
  
  .sidebar-back-rect {
    width: 100%;
  }
  
  .sidebar {
    max-width: 100%;
    padding: var(--spacing-sm);
  }
  
  .sidebar__image {
    max-width: 5rem;
    max-height: 5rem;
  }
  
  .main-content,
  .about {
    max-width: 100%;
    margin: var(--spacing-sm) 0;
    padding: 5%;
  }
  
/* Remove unused about__text class */
  
  .about__research-list {
    font-size: var(--font-size-base);
    padding-left: 5%;
    padding-right: 5%;
    width: 100%;
  }
  
  .about__research-item {
    font-size: var(--font-size-base);
    font-weight: var(--font-weight-light);
    color: var(--color-heading);
  }
  
  .content h1 {
    font-size: var(--font-size-3xl);
  }
  
  .card {
    flex-direction: column;
    gap: var(--spacing-sm);
  }
  
  .card__image {
    max-width: 100%;
  }
  
  .link-card {
    width: 100%;
  }
  
  /* Mobile Navigation */
  .nav-list {
    display: flex;
    flex-direction: column;
    position: fixed;
    top: 3rem;
    padding: 0;
    width: 100%;
    height: 50vh;
    background-color: var(--color-dark);
    align-items: center;
    justify-content: flex-start;
    z-index: var(--z-menu);
    transform: translateY(-100%);
    opacity: 0;
    transition: transform var(--transition-slow), opacity var(--transition-slow);
  }
  
  .nav-list.show {
    transform: translateY(0);
    opacity: 0.9;
  }
  
  .nav-list__item {
    margin: 2% 0;
    font-size: var(--font-size-2xl);
  }
  
  .menu-icon {
    display: flex;
    position: fixed;
    top: 30px;
    right: 20px;
    cursor: pointer;
    flex-direction: column;
    width: 30px;
    z-index: var(--z-hamburger);
    transform: translate(-50%, -50%);
  }
  
  .menu-icon__line {
    width: 20px;
    background-color: var(--color-secondary);
    height: 4px;
    border-radius: 3px;
    margin: 2px 0;
    transition: var(--transition-slower);
  }
  
  .menu-icon.active .menu-icon__line {
    background-color: var(--color-white);
  }
  
  .menu-icon.active .menu-icon__line:nth-child(1) {
    transform: translateY(8px) rotate(45deg);
  }
  
  .menu-icon.active .menu-icon__line:nth-child(2) {
    opacity: 0;
  }
  
  .menu-icon.active .menu-icon__line:nth-child(3) {
    transform: translateY(-8px) rotate(-45deg);
  }
}

/* Extra small devices (portrait phones, less than 576px) */
@media (max-width: 575px) {
  .sidebar h1 {
    font-size: 1.2em;
  }
  
  .sidebar__text {
    font-size: var(--font-size-sm);
  }
  
  .card__title {
    font-size: var(--font-size-lg);
  }
  
  .card__text {
    font-size: var(--font-size-xs);
    text-align: left;
  }
  
  .nav-list__link {
    font-size: 16px;
  }
  
/* Remove unused about__text class */
  
  .about__research-list {
    padding-left: 12%;
    padding-right: 5%;
    padding-bottom: var(--spacing-sm);
    font-size: var(--font-size-base);
    width: 100%;
  }
  
  .about__research-item {
    font-size: var(--font-size-base);
    margin-bottom: 0.4rem;
    font-weight: var(--font-weight-light);
    color: var(--color-heading);
  }
  
  .experience-title,
  .publication-title {
    font-size: var(--font-size-base);
  }
  
  .experience-description {
    font-size: var(--font-size-xs);
    text-align: left;
  }
  
  .experience-duration,
  .publication-date,
  .publication-conference {
    font-size: var(--font-size-xs);
  }
  
  .publication-authors {
    font-size: var(--font-size-xs);
  }
}