/* ========================================
   CSS Custom Properties (Design Tokens)
   ======================================== */
:root {
  /* Light Mode Colors */
  --color-black: #000000;
  --color-dark-grey: #333333;
  --color-medium-grey: #666666;
  --color-light-grey: #f5f5f5;
  --color-white: #ffffff;

  /* Semantic Colors */
  --color-bg-primary: var(--color-white);
  --color-bg-secondary: var(--color-light-grey);
  --color-text-primary: var(--color-black);
  --color-text-secondary: var(--color-dark-grey);
  --color-text-muted: var(--color-medium-grey);
  --color-border: var(--color-black);
  --color-nav-bg: var(--color-white);
  --color-footer-bg: var(--color-black);
  --color-footer-text: var(--color-white);

  /* Typography */
  --font-name: "Times New Roman", Times, serif;
  --font-heading: "Times New Roman", Times, serif;
  --font-body: "Source Sans Pro", "Segoe UI", sans-serif;

  /* Spacing */
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 2rem;
  --spacing-lg: 4rem;
  --spacing-xl: 6rem;

  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition-normal: 0.3s ease;
}

/* Dark Mode */
[data-theme="dark"] {
  --color-bg-primary: #0d0d0d;
  --color-bg-secondary: #1a1a1a;
  --color-text-primary: #ffffff;
  --color-text-secondary: #e0e0e0;
  --color-text-muted: #a0a0a0;
  --color-border: #ffffff;
  --color-nav-bg: #0d0d0d;
  --color-footer-bg: #000000;
  --color-footer-text: #ffffff;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-body);
  font-size: 16px;
  font-weight: 400;
  line-height: 1.6;
  color: var(--color-text-secondary);
  background-color: var(--color-bg-primary);
  transition:
    background-color var(--transition-normal),
    color var(--transition-normal);
}

h1,
h2,
h3,
h4,
h5,
h6 {
  font-family: var(--font-heading);
  font-weight: 500;
  color: var(--color-text-primary);
  line-height: 1.2;
}

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

a:hover {
  opacity: 0.7;
}

ul {
  list-style: none;
}

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

/* ========================================
   Layout
   ======================================== */
.container {
  width: 100%;
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 var(--spacing-md);
}

.section {
  padding: var(--spacing-xl) 0;
}

.section-alt {
  background-color: var(--color-bg-secondary);
}

.section-title {
  font-size: 2rem;
  font-weight: 600;
  margin-bottom: var(--spacing-md);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  position: relative;
  display: inline-block;
}

.section-title::after {
  content: "";
  position: absolute;
  bottom: -0.5rem;
  left: 0;
  width: 3rem;
  height: 2px;
  background-color: var(--color-text-primary);
}

/* ========================================
   Navigation
   ======================================== */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  background-color: var(--color-nav-bg);
  border-bottom: 1px solid var(--color-border);
  z-index: 1000;
  transition: background-color var(--transition-normal);
}

.nav-container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 var(--spacing-md);
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 70px;
}

.nav-logo {
  font-family: var(--font-name);
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--color-text-primary);
  letter-spacing: 0.1em;
}

.nav-menu {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
}

.nav-link {
  font-size: 0.85rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--color-text-secondary);
  padding: var(--spacing-xs) 0;
  position: relative;
}

.nav-link::after {
  content: "";
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 1px;
  background-color: var(--color-text-primary);
  transition: width var(--transition-normal);
}

.nav-link:hover::after,
.nav-link.active::after {
  width: 100%;
}

.nav-link:hover {
  opacity: 1;
}

/* Theme Toggle */
.theme-toggle {
  background: none;
  border: 1px solid var(--color-border);
  padding: var(--spacing-xs);
  cursor: pointer;
  font-size: 1rem;
  line-height: 1;
  color: var(--color-text-primary);
  transition: opacity var(--transition-fast);
}

.theme-toggle:hover {
  opacity: 0.7;
}

/* Mobile Navigation */
.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--spacing-xs);
}

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

.hamburger::before,
.hamburger::after {
  content: "";
  position: absolute;
  left: 0;
  width: 24px;
  height: 2px;
  background-color: var(--color-text-primary);
  transition: transform var(--transition-normal);
}

.hamburger::before {
  top: -7px;
}

.hamburger::after {
  bottom: -7px;
}

/* ========================================
   Hero Section
   ======================================== */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding-top: 70px;
}

.hero-name {
  font-family: var(--font-name);
  font-size: clamp(2.5rem, 8vw, 5rem);
  font-weight: 700;
  letter-spacing: 0.15em;
  margin-bottom: var(--spacing-sm);
}

.hero-title {
  font-size: 1.25rem;
  font-weight: 400;
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-xs);
}

.hero-tagline {
  font-size: 1rem;
  font-style: italic;
  color: var(--color-text-muted);
  margin-bottom: var(--spacing-md);
}

/* Scroll Indicator - Mobile Only */
.scroll-indicator {
  display: none;
  position: absolute;
  bottom: 2rem;
  left: 50%;
  transform: translateX(-50%);
  text-align: center;
  opacity: 1;
  transition: opacity 0.3s ease;
}

.scroll-indicator.hidden {
  opacity: 0;
  pointer-events: none;
}

.scroll-arrow {
  display: inline-block;
  font-size: 1.5rem;
  color: var(--color-text-muted);
  animation: bounce 2s infinite;
}

@keyframes bounce {
  0%, 20%, 50%, 80%, 100% {
    transform: translateY(0);
  }
  40% {
    transform: translateY(-10px);
  }
  60% {
    transform: translateY(-5px);
  }
}

/* ========================================
   Buttons
   ======================================== */
.btn {
  display: inline-block;
  font-family: var(--font-body);
  font-size: 0.9rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  padding: 1rem 2rem;
  border: 1px solid var(--color-border);
  cursor: pointer;
  transition: all var(--transition-fast);
}

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

.btn-primary:hover {
  background-color: transparent;
  color: var(--color-text-primary);
  opacity: 1;
}

/* ========================================
   About Section
   ======================================== */
.about-content {
  max-width: 800px;
}

.about-content p {
  margin-bottom: var(--spacing-sm);
}

.about-content p:last-child {
  margin-bottom: 0;
}

/* ========================================
   Experience Timeline
   ======================================== */
.timeline {
  position: relative;
  padding-left: var(--spacing-lg);
}

.timeline::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  width: 1px;
  background-color: var(--color-border);
}

.timeline-item {
  position: relative;
  padding-bottom: var(--spacing-lg);
}

.timeline-item:last-child {
  padding-bottom: 0;
}

.timeline-item::before {
  content: "";
  position: absolute;
  left: calc(-1 * var(--spacing-lg) - 4px);
  top: 0.5rem;
  width: 9px;
  height: 9px;
  background-color: var(--color-bg-primary);
  border: 1px solid var(--color-border);
}

.timeline-date {
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--color-text-muted);
  margin-bottom: 0.1rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.timeline-role {
  display: block;
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: 0;
}

.timeline-role:hover {
  opacity: 1;
}

.timeline-company {
  display: block;
  font-size: 1rem;
  color: var(--color-text-muted);
  font-style: italic;
  margin-bottom: 0.5rem;
}

.timeline-company:hover {
  opacity: 1;
}

.timeline-details {
  padding-left: var(--spacing-sm);
}

.timeline-details li {
  position: relative;
  padding-left: var(--spacing-sm);
  margin-bottom: 0.5rem;
  font-size: 0.95rem;
}

.timeline-details li::before {
  content: "–";
  position: absolute;
  left: 0;
  color: var(--color-text-muted);
}

/* ========================================
   Skills Section
   ======================================== */
.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--spacing-lg);
}

.skill-category-title {
  font-size: 1rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: var(--spacing-sm);
  font-family: var(--font-body);
}

.skill-pills {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.skill-pill {
  display: inline-block;
  font-size: 0.85rem;
  padding: 0.4rem 0.8rem;
  border: 1px solid var(--color-border);
  background-color: transparent;
  color: var(--color-text-secondary);
  transition: all var(--transition-fast);
}

.skill-pill:hover {
  background-color: var(--color-text-primary);
  color: var(--color-bg-primary);
}

/* ========================================
   Education Section
   ======================================== */
.education-card {
  max-width: 600px;
  padding: var(--spacing-md);
  border: 1px solid var(--color-border);
  background-color: var(--color-bg-primary);
}

.education-degree {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
}

.education-school {
  font-size: 1rem;
  color: var(--color-text-muted);
  font-style: italic;
  margin-bottom: 0.25rem;
}

.education-dates {
  font-size: 0.9rem;
  color: var(--color-text-muted);
  margin-bottom: var(--spacing-sm);
}

.education-details p {
  font-size: 0.95rem;
  margin-bottom: 0.25rem;
}

/* ========================================
   Footer
   ======================================== */
.footer {
  background-color: var(--color-footer-bg);
  color: var(--color-footer-text);
  padding: var(--spacing-xl) 0 var(--spacing-md);
  text-align: center;
}

.footer-title {
  font-size: 2rem;
  font-weight: 500;
  margin-bottom: var(--spacing-md);
  color: var(--color-footer-text);
}

.contact-info {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-lg);
}

.contact-item {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.95rem;
  color: var(--color-footer-text);
}

.contact-icon {
  font-style: normal;
  font-weight: 600;
}

.copyright {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  padding-top: var(--spacing-md);
  border-top: 1px solid rgba(255, 255, 255, 0.1);
}

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

/* Tablet and below */
@media (max-width: 768px) {
  /* Navigation */
  .nav-toggle {
    display: block;
    z-index: 1001;
  }

  .nav-menu {
    position: fixed;
    top: 0;
    right: -100%;
    width: 100%;
    height: 100vh;
    background-color: var(--color-bg-primary);
    flex-direction: column;
    justify-content: center;
    gap: var(--spacing-md);
    transition: right var(--transition-normal);
  }

  .nav-menu.active {
    right: 0;
  }

  .nav-link {
    font-size: 1.5rem;
    padding: var(--spacing-sm) 0;
  }

  /* Hero */
  .hero {
    min-height: 100vh;
    padding-top: 36vh;
    align-items: flex-start;
    padding-bottom: 100px;
    transition: min-height 0.3s ease, padding-top 0.3s ease, padding-bottom 0.3s ease;
  }

  .hero.scrolled {
    min-height: auto;
    padding-top: 100px;
    padding-bottom: var(--spacing-lg);
  }

  .hero-name {
    font-size: 2.5rem;
    letter-spacing: 0.08em;
  }

  .hero-title {
    font-size: 1.1rem;
  }

  .hero-tagline {
    font-size: 0.95rem;
  }

  .scroll-indicator {
    display: block;
  }

  .btn {
    padding: 0.75rem 1.5rem;
    font-size: 0.8rem;
    width: auto;
  }

  /* Sections */
  .section {
    padding: var(--spacing-lg) 0;
  }

  #about {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.5s ease-in-out, transform 0.5s ease-in-out;
  }

  #about.fade-in {
    opacity: 1;
    transform: translateY(0);
  }

  .section-title {
    font-size: 1.5rem;
    margin-bottom: var(--spacing-md);
  }

  .section-title::after {
    width: 2rem;
  }

  /* About */
  .about-content {
    font-size: 0.95rem;
  }

  .about-content p {
    margin-bottom: 0.75rem;
  }

  /* Timeline */
  .timeline {
    padding-left: var(--spacing-sm);
  }

  .timeline::before {
    left: 0;
  }

  .timeline-item::before {
    left: calc(-1 * var(--spacing-sm) - 4px);
    width: 7px;
    height: 7px;
  }

  .timeline-item {
    padding-bottom: var(--spacing-md);
  }

  .timeline-date {
    font-size: 0.75rem;
    margin-bottom: 0.05rem;
  }

  .timeline-role {
    font-size: 1.1rem;
    margin-bottom: 0;
  }

  .timeline-company {
    font-size: 0.9rem;
    margin-bottom: 0.4rem;
  }

  .timeline-details li {
    font-size: 0.9rem;
    line-height: 1.5;
  }

  /* Skills */
  .skills-grid {
    grid-template-columns: 1fr;
    gap: var(--spacing-md);
  }

  .skill-category-title {
    font-size: 0.9rem;
  }

  .skill-pill {
    font-size: 0.8rem;
    padding: 0.35rem 0.65rem;
  }

  /* Education */
  .education-card {
    padding: var(--spacing-sm);
  }

  .education-degree {
    font-size: 0.95rem;
    margin-bottom: 0.1rem;
  }

  .education-school {
    font-size: 0.85rem;
    margin-bottom: 0.05rem;
  }

  .education-dates {
    font-size: 0.85rem;
    margin-bottom: 0.4rem;
  }

  .education-details p {
    font-size: 0.85rem;
  }

  /* Footer */
  .footer {
    padding: var(--spacing-lg) 0 var(--spacing-sm);
  }

  .footer-title {
    font-size: 1.25rem;
    margin-bottom: 0.5rem;
  }

  .contact-info {
    flex-direction: column;
    align-items: center;
    gap: 0.25rem;
  }

  .contact-item {
    font-size: 0.9rem;
    padding: 0.25rem 0;
    justify-content: center;
  }

  .copyright {
    font-size: 0.75rem;
  }
}

/* Mobile phones */
@media (max-width: 480px) {
  .container {
    padding: 0 var(--spacing-sm);
  }

  .hero-name {
    font-size: 2rem;
    letter-spacing: 0.05em;
  }

  .hero-title {
    font-size: 1rem;
  }

  .btn {
    padding: 0.5rem 1rem;
    font-size: 0.7rem;
    text-align: center;
  }

  .timeline {
    padding-left: 0.75rem;
  }

  .timeline-item::before {
    left: calc(-0.75rem - 4px);
  }

  .skill-pills {
    gap: 0.35rem;
  }

  .skill-pill {
    font-size: 0.75rem;
    padding: 0.3rem 0.5rem;
  }
}

/* Touch device optimizations */
@media (hover: none) and (pointer: coarse) {
  .nav-link,
  .skill-pill,
  .contact-item {
    min-height: 44px;
    display: flex;
    align-items: center;
  }

  .btn {
    min-height: 44px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
  }

  .skill-pill {
    min-height: 36px;
  }
}