/* ============================================
   Design System — Personal Website
   "Warm Technical Minimal" for EEE Student
   ============================================ */

/* --- Custom Properties (Design Tokens) --- */
:root {
  /* Colors */
  --color-bg-primary:      #FAF7F2;   /* Warm off-white (main background) */
  --color-bg-secondary:    #F0EBE3;   /* Slightly darker warm (card backgrounds) */
  --color-bg-dark:         #1A1A2E;   /* Deep navy-black (footer, dark areas) */
  --color-text-primary:    #2D2D2D;   /* Near-black (body text, headings) */
  --color-text-secondary:  #6B6B6B;   /* Mid-gray (secondary/muted text) */
  --color-text-on-dark:    #E8E4DF;   /* Warm light (text on dark backgrounds) */
  --color-accent:          #0A7E8C;   /* Deep teal (primary accent) */
  --color-accent-light:    #B8E4E0;   /* Light teal tint (skill bars, tags) */
  --color-accent-hover:    #096B78;   /* Darker teal (hover state) */
  --color-border:          #E0D8CE;   /* Warm border (cards, dividers) */
  --color-shadow:          rgba(45, 45, 45, 0.08);   /* Subtle warm shadow */

  /* Typography */
  --font-heading:  'Inter', 'Segoe UI', system-ui, -apple-system, sans-serif;
  --font-body:     'Inter', 'Segoe UI', system-ui, -apple-system, sans-serif;
  --font-mono:     'JetBrains Mono', 'Fira Code', 'Consolas', monospace;

  --font-size-xs:    0.75rem;    /* 12px */
  --font-size-sm:    0.875rem;   /* 14px */
  --font-size-base:  1rem;       /* 16px */
  --font-size-md:    1.125rem;   /* 18px */
  --font-size-lg:    1.5rem;     /* 24px */
  --font-size-xl:    2rem;       /* 32px */
  --font-size-2xl:   2.5rem;     /* 40px */
  --font-size-hero:  clamp(2rem, 4vw, 3.5rem);

  --font-weight-normal:  400;
  --font-weight-medium:  500;
  --font-weight-bold:    700;

  --line-height-tight:   1.3;
  --line-height-normal:  1.6;
  --line-height-relaxed: 1.8;

  /* Spacing */
  --spacing-xs:    0.25rem;   /* 4px */
  --spacing-sm:    0.5rem;    /* 8px */
  --spacing-md:    1rem;      /* 16px */
  --spacing-lg:    1.5rem;    /* 24px */
  --spacing-xl:    2rem;      /* 32px */
  --spacing-2xl:   3rem;      /* 48px */
  --spacing-3xl:   4rem;      /* 64px */
  --spacing-section: clamp(3rem, 6vw, 6rem);

  /* Layout */
  --max-width:       1200px;
  --nav-height:      72px;
  --content-padding: clamp(1rem, 3vw, 2rem);

  /* Borders & Shadows */
  --radius-sm:   4px;
  --radius-md:   8px;
  --radius-lg:   12px;
  --radius-full: 9999px;

  --shadow-sm:   0 2px 4px var(--color-shadow);
  --shadow-md:   0 4px 8px var(--color-shadow);
  --shadow-lg:   0 8px 24px var(--color-shadow);
  --shadow-card: 0 4px 12px var(--color-shadow);
  --shadow-card-hover: 0 8px 24px rgba(45, 45, 45, 0.15);

  /* Transitions */
  --transition-fast:   150ms ease;
  --transition-base:   300ms ease;
  --transition-slow:   600ms ease-out;
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: var(--nav-height);
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-body);
  font-size: var(--font-size-base);
  line-height: var(--line-height-normal);
  color: var(--color-text-primary);
  background-color: var(--color-bg-primary);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

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

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

ul, ol {
  list-style: none;
}

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

/* ============================================
   Layout Utilities
   ============================================ */
.container {
  max-width: var(--max-width);
  margin-inline: auto;
  padding-inline: var(--content-padding);
}

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

.section-heading {
  font-size: var(--font-size-xl);
  font-weight: var(--font-weight-bold);
  color: var(--color-text-primary);
  margin-bottom: var(--spacing-xl);
  position: relative;
}

.section-heading::after {
  content: '';
  display: block;
  width: 40px;
  height: 3px;
  background-color: var(--color-accent);
  margin-top: var(--spacing-sm);
}

/* ============================================
   Typography
   ============================================ */
h1, h2, h3, h4 {
  font-family: var(--font-heading);
  line-height: var(--line-height-tight);
}

h1 { font-size: var(--font-size-hero); }
h2 { font-size: var(--font-size-xl); }
h3 { font-size: var(--font-size-lg); }
h4 { font-size: var(--font-size-md); }

p {
  margin-bottom: var(--spacing-md);
  line-height: var(--line-height-relaxed);
}

/* ============================================
   Buttons
   ============================================ */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-sm);
  padding: var(--spacing-sm) var(--spacing-lg);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  border-radius: var(--radius-md);
  transition: background-color var(--transition-fast),
              transform var(--transition-fast),
              box-shadow var(--transition-fast);
}

.btn-primary {
  background-color: var(--color-accent);
  color: #fff;
}

.btn-primary:hover {
  background-color: var(--color-accent-hover);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

.btn-outline {
  border: 2px solid var(--color-accent);
  color: var(--color-accent);
  background: transparent;
}

.btn-outline:hover {
  background-color: var(--color-accent);
  color: #fff;
  transform: translateY(-1px);
}

/* ============================================
   Reveal Animation
   ============================================ */
.reveal {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity var(--transition-slow), transform var(--transition-slow);
}

.reveal.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ============================================
   Navigation Bar
   ============================================ */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--nav-height);
  background-color: rgba(250, 247, 242, 0.95);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  z-index: 1000;
  border-bottom: 1px solid var(--color-border);
}

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

.nav-logo {
  font-size: var(--font-size-md);
  font-weight: var(--font-weight-bold);
  color: var(--color-text-primary);
}

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

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

.nav-link {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--color-text-secondary);
  transition: color var(--transition-fast);
  position: relative;
}

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

.nav-link[aria-current="section"] {
  color: var(--color-accent);
}

.nav-link[aria-current="section"]::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  right: 0;
  height: 2px;
  background-color: var(--color-accent);
  border-radius: var(--radius-sm);
}

/* Hamburger button (hidden on desktop) */
.menu-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  padding: var(--spacing-sm);
  z-index: 1001;
}

.menu-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background-color: var(--color-text-primary);
  transition: transform var(--transition-base), opacity var(--transition-base);
}

.menu-toggle[aria-expanded="true"] span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.menu-toggle[aria-expanded="true"] span:nth-child(2) {
  opacity: 0;
}

.menu-toggle[aria-expanded="true"] span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* ============================================
   Hero Section
   ============================================ */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  padding-top: var(--nav-height);
}

.hero .container {
  display: grid;
  grid-template-columns: 1fr 1.5fr;
  gap: var(--spacing-3xl);
  align-items: center;
}

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

.hero-image {
  width: 180px;
  height: 180px;
  border-radius: var(--radius-full);
  object-fit: cover;
  box-shadow: var(--shadow-lg);
}

.hero-content {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

.hero-greeting {
  font-size: var(--font-size-hero);
  font-weight: var(--font-weight-bold);
  color: var(--color-text-primary);
}

.hero-greeting .accent {
  color: var(--color-accent);
}

.hero-subtitle {
  font-size: var(--font-size-md);
  color: var(--color-text-secondary);
  font-weight: var(--font-weight-medium);
}

.hero-tagline {
  font-size: var(--font-size-base);
  color: var(--color-text-secondary);
}

.hero-actions {
  display: flex;
  gap: var(--spacing-md);
  margin-top: var(--spacing-sm);
}

/* ============================================
   About Section
   ============================================ */
.about-text {
  max-width: 800px;
  color: var(--color-text-primary);
}

.quick-facts {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--spacing-md);
  margin-top: var(--spacing-xl);
}

.fact-item {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
}

.fact-icon {
  width: 20px;
  height: 20px;
  color: var(--color-accent);
  flex-shrink: 0;
}

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

.skill-group {
  background-color: var(--color-bg-secondary);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--spacing-xl);
}

.skill-group-title {
  font-size: var(--font-size-md);
  font-weight: var(--font-weight-bold);
  color: var(--color-text-primary);
  margin-bottom: var(--spacing-lg);
}

.skill-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--spacing-md);
}

.skill-item:last-child {
  margin-bottom: 0;
}

.skill-name {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--color-text-primary);
  width: 160px;
  flex-shrink: 0;
}

.skill-bar {
  flex: 1;
  height: 8px;
  background-color: var(--color-border);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.skill-bar-fill {
  height: 100%;
  width: 0%;
  background-color: var(--color-accent);
  border-radius: var(--radius-full);
  transition: width 1.2s ease-out;
}

.skill-level {
  font-size: var(--font-size-xs);
  font-family: var(--font-mono);
  color: var(--color-text-secondary);
  width: 90px;
  flex-shrink: 0;
  text-align: right;
}

/* ============================================
   Projects Section
   ============================================ */
.projects-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--spacing-xl);
}

.project-card {
  background-color: var(--color-bg-secondary);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: transform var(--transition-base), box-shadow var(--transition-base);
}

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

.project-image {
  width: 100%;
  aspect-ratio: 16 / 9;
  object-fit: cover;
}

.project-content {
  padding: var(--spacing-lg);
}

.project-title {
  font-size: var(--font-size-md);
  font-weight: var(--font-weight-bold);
  color: var(--color-text-primary);
  margin-bottom: var(--spacing-xs);
}

.project-tag {
  font-size: var(--font-size-xs);
  font-family: var(--font-mono);
  color: var(--color-accent);
  font-weight: var(--font-weight-medium);
  margin-bottom: var(--spacing-md);
}

.project-description {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  line-height: var(--line-height-normal);
  margin-bottom: var(--spacing-md);
}

.project-tech-tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-sm);
}

.tech-tag {
  font-size: var(--font-size-xs);
  font-family: var(--font-mono);
  padding: var(--spacing-xs) var(--spacing-sm);
  background-color: var(--color-accent-light);
  color: var(--color-accent-hover);
  border-radius: var(--radius-sm);
}

/* ============================================
   Internship Section
   ============================================ */
.internship-section {
  background-color: var(--color-bg-secondary);
}

.timeline {
  position: relative;
  padding-left: 2rem;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  width: 2px;
  background-color: var(--color-border);
}

.timeline-item {
  position: relative;
  padding-bottom: var(--spacing-2xl);
}

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

.timeline-dot {
  position: absolute;
  left: -2rem;
  top: 4px;
  width: 12px;
  height: 12px;
  border-radius: var(--radius-full);
  background-color: var(--color-accent);
  border: 2px solid var(--color-bg-secondary);
  transform: translateX(-5px);
}

.timeline-date {
  font-size: var(--font-size-sm);
  font-family: var(--font-mono);
  color: var(--color-accent);
  font-weight: var(--font-weight-medium);
  margin-bottom: var(--spacing-xs);
}

.timeline-title {
  font-size: var(--font-size-md);
  font-weight: var(--font-weight-bold);
  color: var(--color-text-primary);
  margin-bottom: var(--spacing-xs);
}

.timeline-company {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-sm);
}

.timeline-description {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  line-height: var(--line-height-normal);
  max-width: 600px;
}

.timeline-highlights {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-sm);
  margin-top: var(--spacing-md);
}

.highlight-tag {
  font-size: var(--font-size-xs);
  font-family: var(--font-mono);
  padding: var(--spacing-xs) var(--spacing-sm);
  background-color: var(--color-accent-light);
  color: var(--color-accent-hover);
  border-radius: var(--radius-sm);
}

/* ============================================
   Education Section
   ============================================ */
.education-timeline {
  position: relative;
  padding-left: 2rem;
}

.education-timeline::before {
  content: '';
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  width: 2px;
  background-color: var(--color-border);
}

.education-item {
  position: relative;
  padding-bottom: var(--spacing-2xl);
}

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

.education-dot {
  position: absolute;
  left: -2rem;
  top: 4px;
  width: 12px;
  height: 12px;
  border-radius: var(--radius-full);
  background-color: var(--color-accent);
  border: 2px solid var(--color-bg-primary);
  transform: translateX(-5px);
}

.education-date {
  font-size: var(--font-size-sm);
  font-family: var(--font-mono);
  color: var(--color-accent);
  font-weight: var(--font-weight-medium);
  margin-bottom: var(--spacing-xs);
}

.education-degree {
  font-size: var(--font-size-md);
  font-weight: var(--font-weight-bold);
  color: var(--color-text-primary);
  margin-bottom: var(--spacing-xs);
}

.education-school {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-sm);
}

.education-details {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  line-height: var(--line-height-normal);
}

.education-details .course-list {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-sm);
  margin-top: var(--spacing-sm);
}

.course-tag {
  font-size: var(--font-size-xs);
  font-family: var(--font-mono);
  padding: var(--spacing-xs) var(--spacing-sm);
  background-color: var(--color-accent-light);
  color: var(--color-accent-hover);
  border-radius: var(--radius-sm);
}

/* ============================================
   Footer
   ============================================ */
.footer {
  background-color: var(--color-bg-dark);
  color: var(--color-text-on-dark);
  padding-block: var(--spacing-xl);
}

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

.footer-copyright {
  font-size: var(--font-size-sm);
  color: var(--color-text-on-dark);
}

.footer-links {
  display: flex;
  gap: var(--spacing-lg);
}

.footer-link {
  font-size: var(--font-size-sm);
  color: var(--color-text-on-dark);
  transition: color var(--transition-fast);
}

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

.footer-link svg {
  width: 20px;
  height: 20px;
  fill: currentColor;
}

.back-to-top {
  font-size: var(--font-size-sm);
  color: var(--color-text-on-dark);
  transition: color var(--transition-fast);
}

.back-to-top:hover {
  color: var(--color-accent);
}

/* ============================================
   Responsive — Mobile (< 768px)
   ============================================ */
@media (max-width: 767px) {
  /* Navigation */
  .menu-toggle {
    display: flex;
  }

  .nav-menu {
    position: fixed;
    top: var(--nav-height);
    left: 0;
    right: 0;
    background-color: rgba(250, 247, 242, 0.98);
    backdrop-filter: blur(10px);
    flex-direction: column;
    align-items: center;
    padding: var(--spacing-xl);
    gap: var(--spacing-lg);
    transform: translateY(-120%);
    opacity: 0;
    transition: transform var(--transition-base), opacity var(--transition-base);
    border-bottom: 1px solid var(--color-border);
  }

  .nav-menu.open {
    transform: translateY(0);
    opacity: 1;
  }

  /* Hero */
  .hero .container {
    grid-template-columns: 1fr;
    text-align: center;
    gap: var(--spacing-xl);
  }

  .hero-content {
    align-items: center;
  }

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

  .hero-image {
    width: 140px;
    height: 140px;
  }

  /* Quick Facts */
  .quick-facts {
    grid-template-columns: repeat(2, 1fr);
  }

  /* Skills */
  .skill-item {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--spacing-xs);
  }

  .skill-bar {
    margin-left: 0;
    width: 100%;
  }

  .skill-level {
    text-align: left;
  }

  /* Projects */
  .projects-grid {
    grid-template-columns: 1fr;
  }

  /* Timeline (Internship & Education) */
  .timeline,
  .education-timeline {
    padding-left: 1.5rem;
  }

  .timeline-dot,
  .education-dot {
    left: -1.5rem;
  }

  /* Footer */
  .footer .container {
    flex-direction: column;
    gap: var(--spacing-md);
    text-align: center;
  }
}

/* ============================================
   Responsive — Tablet (768px - 1023px)
   ============================================ */
@media (min-width: 768px) and (max-width: 1023px) {
  /* Skills grid can show 2 columns */
  .skills-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  /* Quick Facts */
  .quick-facts {
    grid-template-columns: repeat(3, 1fr);
  }
}

/* ============================================
   Responsive — Desktop (≥ 1024px)
   ============================================ */
@media (min-width: 1024px) {
  /* Skills grid: 3 columns */
  .skills-grid {
    grid-template-columns: repeat(3, 1fr);
  }

  /* Projects grid: 2 columns (already set) */
}

/* ============================================
   Accessibility
   ============================================ */
:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  .reveal {
    opacity: 1;
    transform: none;
    transition: none;
  }

  .skill-bar-fill {
    transition: none;
  }

  .project-card {
    transition: none;
  }

  .btn {
    transition: none;
  }
}