/* ==========================================================================
   1. CSS VARIABLES / THEME
   ========================================================================== */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&display=swap');

/* Default (Light Theme) */
:root,
html[data-theme="light"] {
  --color-bg: #F7F7F5;
  --color-surface: #FFFFFF;
  --color-text-primary: #111111;
  --color-text-secondary: #555555;
  --color-text-muted: #777777;
  --color-border: #DDDDDD;
  --color-border-hover: #111111;

  --color-btn-primary-bg: #111111;
  --color-btn-primary-text: #F7F7F5;
  --color-btn-primary-hover-bg: #2A2A2A;

  --color-btn-secondary-bg: transparent;
  --color-btn-secondary-text: #111111;
  --color-btn-secondary-border: #DDDDDD;
  --color-btn-secondary-hover-bg: #EAEAE8;

  --color-badge-bg: #F0F0EE;
  --color-badge-text: #333333;
  --color-badge-border: #DDDDDD;

  --header-bg: rgba(247, 247, 245, 0.9);

  /* Typography */
  --font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;

  --font-size-xs: 0.8125rem;  /* 13px */
  --font-size-sm: 0.875rem;   /* 14px */
  --font-size-base: 1rem;     /* 16px */
  --font-size-lg: 1.125rem;   /* 18px */
  --font-size-xl: 1.25rem;    /* 20px */
  --font-size-2xl: 1.5rem;    /* 24px */
  --font-size-3xl: 2rem;      /* 32px */
  --font-size-4xl: 2.75rem;   /* 44px */
  --font-size-5xl: 3.5rem;    /* 56px */

  --font-weight-light: 300;
  --font-weight-regular: 400;
  --font-weight-medium: 500;
  --font-weight-semibold: 600;
  --font-weight-bold: 700;

  --line-height-tight: 1.15;
  --line-height-heading: 1.25;
  --line-height-body: 1.65;

  /* Spacing Scale */
  --space-1: 8px;
  --space-2: 12px;
  --space-3: 16px;
  --space-4: 24px;
  --space-5: 32px;
  --space-6: 48px;
  --space-7: 64px;
  --space-8: 96px;
  --space-9: 128px;

  /* Layout & Geometry */
  --container-max-width: 1280px;
  --header-height: 72px;
  --radius-sm: 4px;
  --radius-md: 6px;
  --radius-lg: 12px;
  --radius-full: 9999px;

  /* Transitions */
  --transition-fast: 0.15s cubic-bezier(0.16, 1, 0.3, 1);
  --transition-normal: 0.25s cubic-bezier(0.16, 1, 0.3, 1);
}

/* Dark Theme Overrides */
html[data-theme="dark"] {
  --color-bg: #0A0A0A;
  --color-surface: #141414;
  --color-text-primary: #F5F5F5;
  --color-text-secondary: #999999;
  --color-text-muted: #777777;
  --color-border: #242424;
  --color-border-hover: #F5F5F5;

  --color-btn-primary-bg: #F5F5F5;
  --color-btn-primary-text: #0A0A0A;
  --color-btn-primary-hover-bg: #D9D9D9;

  --color-btn-secondary-bg: transparent;
  --color-btn-secondary-text: #F5F5F5;
  --color-btn-secondary-border: #242424;
  --color-btn-secondary-hover-bg: #1F1F1F;

  --color-badge-bg: #141414;
  --color-badge-text: #CCCCCC;
  --color-badge-border: #242424;

  --header-bg: rgba(10, 10, 10, 0.9);
}


/* ==========================================================================
   2. RESET / BASE STYLES & LAYOUT SYSTEM
   ========================================================================== */

*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-family: var(--font-family);
  font-size: 16px;
  background-color: var(--color-bg);
  color: var(--color-text-primary);
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-height) + var(--space-4));
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
}

body {
  min-height: 100vh;
  line-height: var(--line-height-body);
  overflow-x: hidden;
  background-color: var(--color-bg);
  color: var(--color-text-primary);
  transition: background-color var(--transition-normal), color var(--transition-normal);
}

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

ul, ol {
  list-style: none;
}

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

button, input, textarea, select {
  font: inherit;
  color: inherit;
}

/* 
   UNIFIED CENTERED CONTAINER ARCHITECTURE
   All sections use the exact same left-aligned 1280px grid boundary.
*/
.container {
  width: min(100% - 64px, var(--container-max-width));
  margin-inline: auto;
}

main {
  width: 100%;
}

section {
  width: 100%;
  padding: var(--space-8) 0;
  border-bottom: 1px solid var(--color-border);
}

section:last-of-type {
  border-bottom: none;
}


/* ==========================================================================
   3. TYPOGRAPHY
   ========================================================================== */

h1, h2, h3, h4, h5, h6 {
  color: var(--color-text-primary);
  font-weight: var(--font-weight-semibold);
  line-height: var(--line-height-heading);
  letter-spacing: -0.025em;
}

p {
  color: var(--color-text-secondary);
  font-weight: var(--font-weight-regular);
}

section h2 {
  font-size: clamp(1.75rem, 2.5vw + 1rem, 2.25rem);
  font-weight: var(--font-weight-bold);
  margin-bottom: var(--space-3);
  letter-spacing: -0.03em;
}

.section-desc {
  font-size: var(--font-size-lg);
  color: var(--color-text-secondary);
  max-width: 750px;
  margin-bottom: var(--space-6);
  line-height: var(--line-height-body);
}


/* ==========================================================================
   4. HEADER / NAVIGATION
   ========================================================================== */

header {
  position: sticky;
  top: 0;
  z-index: 100;
  width: 100%;
  background-color: var(--header-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border);
  transition: background-color var(--transition-fast), border-color var(--transition-fast);
}

nav.container {
  height: var(--header-height);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
}

.brand-logo {
  font-size: var(--font-size-xl);
  font-weight: var(--font-weight-bold);
  letter-spacing: -0.03em;
  color: var(--color-text-primary);
  flex-shrink: 0;
}

.brand-logo:hover {
  opacity: 0.8;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  margin-left: auto;
}

.nav-links li a {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--color-text-secondary);
  position: relative;
  padding: var(--space-1) 0;
}

.nav-links li a:hover {
  color: var(--color-text-primary);
}

.nav-links li a::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 1px;
  background-color: var(--color-text-primary);
  transition: width var(--transition-fast);
}

.nav-links li a:hover::after {
  width: 100%;
}

/* Theme toggle button */
.theme-toggle {
  background: transparent;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  color: var(--color-text-primary);
  width: 38px;
  height: 38px;
  padding: 0;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  transition: border-color var(--transition-fast), background-color var(--transition-fast), transform var(--transition-fast);
}

.theme-toggle:hover {
  border-color: var(--color-text-primary);
  background-color: var(--color-btn-secondary-hover-bg);
}

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

html[data-theme="dark"] .sun-icon {
  display: block;
}

html[data-theme="dark"] .moon-icon {
  display: none;
}

html[data-theme="light"] .sun-icon,
:root:not([data-theme="dark"]) .sun-icon {
  display: none;
}

html[data-theme="light"] .moon-icon,
:root:not([data-theme="dark"]) .moon-icon {
  display: block;
}


/* ==========================================================================
   5. HERO (#home)
   ========================================================================== */

#home {
  padding-top: var(--space-8);
  padding-bottom: var(--space-8);
}

.hero-container {
  display: grid;
  grid-template-columns: 58% 42%;
  gap: var(--space-6);
  align-items: center;
}

.hero-text {
  max-width: 680px;
}

.hero-greeting {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: var(--space-2);
}

.hero-text h1 {
  font-size: clamp(2.5rem, 4vw + 1.2rem, 3.6rem);
  font-weight: var(--font-weight-bold);
  letter-spacing: -0.04em;
  line-height: var(--line-height-tight);
  margin-bottom: var(--space-2);
}

.hero-text h2 {
  font-size: clamp(1.125rem, 1.5vw + 0.8rem, 1.35rem);
  font-weight: var(--font-weight-medium);
  color: var(--color-text-secondary);
  line-height: var(--line-height-heading);
  margin-bottom: var(--space-4);
}

.hero-bio {
  font-size: var(--font-size-lg);
  color: var(--color-text-secondary);
  line-height: var(--line-height-body);
  margin-bottom: var(--space-6);
}

.hero-cta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-3) var(--space-5);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
  cursor: pointer;
}

.btn-primary {
  background-color: var(--color-btn-primary-bg);
  color: var(--color-btn-primary-text);
  border: 1px solid var(--color-btn-primary-bg);
}

.btn-primary:hover {
  background-color: var(--color-btn-primary-hover-bg);
  border-color: var(--color-btn-primary-hover-bg);
  transform: translateY(-2px);
}

.btn-secondary {
  background-color: var(--color-btn-secondary-bg);
  color: var(--color-btn-secondary-text);
  border: 1px solid var(--color-btn-secondary-border);
}

.btn-secondary:hover {
  background-color: var(--color-btn-secondary-hover-bg);
  border-color: var(--color-text-primary);
  transform: translateY(-2px);
}

.hero-image {
  display: flex;
  justify-content: center;
  align-items: center;
}

.hero-image img {
  width: 100%;
  max-width: 360px;
  aspect-ratio: 1 / 1;
  object-fit: cover;
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border);
  transition: border-color var(--transition-normal), transform var(--transition-normal);
}

.hero-image img:hover {
  border-color: var(--color-border-hover);
  transform: translateY(-3px);
}


/* ==========================================================================
   6. ABOUT (#about)
   ========================================================================== */

.about-content {
  max-width: 820px;
}

.about-content p {
  font-size: var(--font-size-lg);
  line-height: 1.75;
  color: var(--color-text-secondary);
  margin-bottom: var(--space-4);
}

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


/* ==========================================================================
   7. SKILLS (#skills)
   ========================================================================== */

.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(230px, 1fr));
  gap: var(--space-4);
}

.skills-grid article {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: var(--space-4) var(--space-5);
  transition: border-color var(--transition-fast), transform var(--transition-fast);
}

.skills-grid article:hover {
  border-color: var(--color-border-hover);
  transform: translateY(-2px);
}

.skills-grid article h3 {
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
  margin-bottom: var(--space-3);
  padding-bottom: var(--space-2);
  border-bottom: 1px solid var(--color-border);
}

.skills-grid article ul {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.skills-grid article ul li {
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-medium);
  color: var(--color-badge-text);
  background-color: var(--color-badge-bg);
  border: 1px solid var(--color-badge-border);
  padding: 4px 10px;
  border-radius: var(--radius-sm);
  transition: border-color var(--transition-fast), color var(--transition-fast);
}

.skills-grid article ul li:hover {
  border-color: var(--color-text-secondary);
  color: var(--color-text-primary);
}


/* ==========================================================================
   8. PROJECTS (#projects)
   ========================================================================== */

.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: var(--space-5);
}

.projects-grid article {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: var(--space-5);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  transition: border-color var(--transition-fast), transform var(--transition-fast);
}

.projects-grid article:hover {
  border-color: var(--color-border-hover);
  transform: translateY(-3px);
}

.projects-grid article h3 {
  font-size: var(--font-size-xl);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
  margin-bottom: var(--space-2);
  letter-spacing: -0.02em;
}

.projects-grid article p {
  font-size: var(--font-size-base);
  color: var(--color-text-secondary);
  line-height: var(--line-height-body);
  margin-bottom: var(--space-5);
  flex-grow: 1;
}

.project-links {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.project-links a {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--color-text-primary);
  padding: var(--space-2) var(--space-3);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background-color: transparent;
  transition: all var(--transition-fast);
}

.project-links a:hover {
  border-color: var(--color-text-primary);
  background-color: var(--color-btn-secondary-hover-bg);
}

.project-links a::after {
  content: "→";
  font-family: inherit;
  transition: transform var(--transition-fast);
}

.project-links a:hover::after {
  transform: translateX(3px);
}


/* ==========================================================================
   9. EDUCATION (#education)
   ========================================================================== */

.education-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: var(--space-5);
  transition: border-color var(--transition-fast), transform var(--transition-fast);
  max-width: 820px;
}

.education-card:hover {
  border-color: var(--color-border-hover);
  transform: translateY(-2px);
}

.education-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin-bottom: var(--space-2);
}

.education-header h3 {
  font-size: var(--font-size-xl);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
}

.education-badge {
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-medium);
  color: var(--color-badge-text);
  background-color: var(--color-badge-bg);
  border: 1px solid var(--color-badge-border);
  padding: 4px 12px;
  border-radius: var(--radius-full);
}

.education-institution {
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-medium);
  color: var(--color-text-primary);
  margin-bottom: 2px;
}

.education-university {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
}


/* ==========================================================================
   10. CONTACT (#contact)
   ========================================================================== */

.contact-heading {
  font-size: clamp(1.5rem, 2.5vw + 1rem, 2rem);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
  margin-bottom: var(--space-2);
  letter-spacing: -0.025em;
}

.contact-desc {
  font-size: var(--font-size-lg);
  color: var(--color-text-secondary);
  max-width: 750px;
  margin-bottom: var(--space-6);
  line-height: var(--line-height-body);
}

.contact-cards {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-4);
}

.contact-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: var(--space-5);
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  transition: border-color var(--transition-fast), transform var(--transition-fast), background-color var(--transition-fast);
}

.contact-card:hover {
  border-color: var(--color-border-hover);
  transform: translateY(-3px);
  background-color: var(--color-btn-secondary-hover-bg);
}

.contact-label {
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-semibold);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-text-muted);
}

.contact-value {
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2);
  word-break: break-all;
}

.contact-value svg {
  flex-shrink: 0;
  transition: transform var(--transition-fast);
}

.contact-card:hover .contact-value svg {
  transform: translateX(4px);
}


/* ==========================================================================
   11. FOOTER
   ========================================================================== */

footer {
  width: 100%;
  border-top: 1px solid var(--color-border);
  padding: var(--space-6) 0;
}

.footer-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

footer p {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
}


/* ==========================================================================
   12. RESPONSIVE STYLES
   ========================================================================== */

@media (max-width: 1024px) {
  .hero-container {
    grid-template-columns: 55% 45%;
    gap: var(--space-5);
  }

  .hero-image img {
    max-width: 320px;
  }
}

@media (max-width: 900px) {
  .contact-cards {
    grid-template-columns: 1fr;
    gap: var(--space-3);
  }
}

@media (max-width: 768px) {
  .container {
    width: min(100% - 32px, var(--container-max-width));
  }

  nav.container {
    height: auto;
    padding-block: 14px;
    flex-wrap: wrap;
  }

  .nav-links {
    order: 3;
    width: 100%;
    justify-content: center;
    gap: var(--space-3);
    padding-top: var(--space-2);
    border-top: 1px solid var(--color-border);
    margin-left: 0;
  }

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

  .hero-text {
    max-width: 100%;
  }

  .hero-image {
    justify-content: center;
  }

  .hero-image img {
    max-width: 280px;
  }

  .projects-grid,
  .skills-grid {
    grid-template-columns: 1fr;
  }

  section {
    padding: var(--space-6) 0;
  }

  .footer-container {
    flex-direction: column;
    align-items: flex-start;
  }
}

@media (max-width: 480px) {
  .container {
    width: min(100% - 24px, var(--container-max-width));
  }

  .hero-cta {
    flex-direction: column;
  }

  .btn {
    width: 100%;
  }

  .nav-links li a {
    font-size: var(--font-size-xs);
  }

  .education-header {
    flex-direction: column;
    align-items: flex-start;
  }
}


/* ==========================================================================
   13. REDUCED-MOTION PREFERENCES
   ========================================================================== */

@media (prefers-reduced-motion: reduce) {
  *, ::before, ::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}