/* ==========================================================================
   Variables & Reset
   ========================================================================== */
:root {
  /* Color Palette - Minimal x Developer x Game */
  --bg-color: #fafafa;
  --bg-card: #ffffff;
  --text-main: #111827;
  --text-muted: #6b7280;
  --text-light: #9ca3af;
  --border-color: #e5e7eb;
  --border-dark: #111827;
  
  /* Accent Color (Cyan/Teal Tech Accent) */
  --accent: #0284c7;
  --accent-light: #e0f2fe;
  --accent-hover: #0369a1;

  /* Typography */
  --font-sans: 'Inter', 'Noto Sans JP', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-mono: 'Fira Code', monospace;

  /* Layout */
  --max-width: 1000px;
  --header-height: 70px;

  /* Transitions */
  --transition-fast: 0.2s cubic-bezier(0.16, 1, 0.3, 1);
  --transition-normal: 0.4s cubic-bezier(0.16, 1, 0.3, 1);
}

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  background-color: var(--bg-color);
  color: var(--text-main);
  font-family: var(--font-sans);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  position: relative;
  overflow-x: hidden;
}

/* Background grid decorator */
.bg-grid {
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  background-image: 
    linear-gradient(to right, rgba(0, 0, 0, 0.03) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(0, 0, 0, 0.03) 1px, transparent 1px);
  background-size: 40px 40px;
  pointer-events: none;
  z-index: -1;
}

/* Typography elements */
h1, h2, h3, h4 {
  font-weight: 700;
  line-height: 1.2;
  color: var(--text-main);
}

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

ul {
  list-style: none;
}

/* Utility Container */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

.section {
  padding: 100px 0;
  border-bottom: 1px solid var(--border-color);
}

/* Section Header */
.section-header {
  display: flex;
  align-items: baseline;
  gap: 12px;
  margin-bottom: 40px;
}

.section-num {
  font-family: var(--font-mono);
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--accent);
}

.section-title {
  font-size: 1.75rem;
  letter-spacing: -0.02em;
  font-family: var(--font-mono);
  text-transform: uppercase;
}

.section-intro {
  color: var(--text-muted);
  font-size: 1rem;
  margin-top: -24px;
  margin-bottom: 48px;
}

/* ==========================================================================
   Header & Navigation
   ========================================================================== */
.header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: var(--header-height);
  background-color: rgba(250, 250, 250, 0.85);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border-color);
  z-index: 100;
  display: flex;
  align-items: center;
}

.header-container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: 1.25rem;
  letter-spacing: -0.03em;
}

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

.nav ul {
  display: flex;
  gap: 32px;
}

.nav a {
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-muted);
  transition: color var(--transition-fast);
}

.nav a:hover {
  color: var(--text-main);
}

.nav-num {
  font-family: var(--font-mono);
  color: var(--accent);
  font-size: 0.8rem;
  margin-right: 4px;
}

/* ==========================================================================
   1. Hero Section
   ========================================================================== */
.hero {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  position: relative;
  padding: calc(var(--header-height) + 40px) 24px 60px 24px;
  max-width: var(--max-width);
  margin: 0 auto;
}

.hero-tag {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--accent);
  letter-spacing: 0.05em;
  margin-bottom: 16px;
}

.code-bracket {
  color: var(--text-light);
}

.hero-title {
  font-size: clamp(3.5rem, 8vw, 6rem);
  font-weight: 800;
  letter-spacing: -0.04em;
  line-height: 1;
  margin-bottom: 16px;
  text-transform: uppercase;
}

.hero-subtitle {
  font-family: var(--font-mono);
  font-size: clamp(1.2rem, 3vw, 1.75rem);
  color: var(--text-muted);
  margin-bottom: 24px;
  font-weight: 500;
}

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

.hero-description {
  font-size: 1.1rem;
  color: var(--text-muted);
  max-width: 600px;
  margin-bottom: 40px;
}

.hero-actions {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 24px;
  border-radius: 4px;
  font-size: 0.95rem;
  font-weight: 600;
  font-family: var(--font-mono);
  transition: all var(--transition-fast);
  cursor: pointer;
}

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

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

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

.btn-secondary:hover {
  border-color: var(--text-main);
  background-color: rgba(0, 0, 0, 0.03);
  transform: translateY(-2px);
}

/* Scroll indicator */
.scroll-indicator {
  position: absolute;
  bottom: 40px;
  left: 24px;
  display: flex;
  align-items: center;
  gap: 12px;
}

.scroll-text {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text-light);
  letter-spacing: 0.1em;
}

.scroll-line {
  width: 40px;
  height: 1px;
  background-color: var(--text-light);
}

/* ==========================================================================
   2. About Section
   ========================================================================== */
.about-grid {
  display: grid;
  grid-template-columns: 1.2fr 1fr;
  gap: 48px;
}

.bio-heading {
  font-size: 1.35rem;
  margin-bottom: 20px;
  line-height: 1.4;
}

.about-bio p {
  color: var(--text-muted);
  margin-bottom: 16px;
}

.skills-heading {
  font-family: var(--font-mono);
  font-size: 1rem;
  margin-bottom: 24px;
  color: var(--text-main);
  letter-spacing: 0.05em;
}

.accent-symbol {
  color: var(--accent);
}

.skills-wrapper {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.skill-category-label {
  display: block;
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--text-light);
  margin-bottom: 8px;
  text-transform: uppercase;
}

.skill-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.tag {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  padding: 6px 12px;
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 4px;
  color: var(--text-main);
  transition: all var(--transition-fast);
}

.tag:hover {
  border-color: var(--accent);
  color: var(--accent);
}

/* ==========================================================================
   3. Experience Section (Vertical Timeline)
   ========================================================================== */
.timeline {
  position: relative;
  max-width: 800px;
  margin-top: 32px;
}

/* Vertical line */
.timeline::before {
  content: '';
  position: absolute;
  top: 0;
  left: 95px;
  width: 2px;
  height: 100%;
  background-color: var(--border-color);
}

.timeline-item {
  position: relative;
  display: flex;
  align-items: flex-start;
  margin-bottom: 48px;
}

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

.timeline-meta {
  width: 80px;
  text-align: right;
  padding-right: 20px;
  flex-shrink: 0;
}

.timeline-year {
  font-family: var(--font-mono);
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--accent);
}

.timeline-marker {
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background-color: var(--bg-color);
  border: 3px solid var(--text-main);
  position: relative;
  left: 10px;
  top: 6px;
  z-index: 2;
  flex-shrink: 0;
  transition: transform var(--transition-fast), background-color var(--transition-fast);
}

.timeline-item:hover .timeline-marker {
  background-color: var(--accent);
  border-color: var(--accent);
  transform: scale(1.2);
}

.timeline-content {
  margin-left: 36px;
  background-color: var(--bg-card);
  padding: 24px;
  border-radius: 6px;
  border: 1px solid var(--border-color);
  width: 100%;
  transition: border-color var(--transition-fast), transform var(--transition-fast);
}

.timeline-item:hover .timeline-content {
  border-color: var(--border-dark);
  transform: translateX(4px);
}

.timeline-title {
  font-size: 1.15rem;
  margin-bottom: 8px;
}

.timeline-desc {
  font-size: 0.95rem;
  color: var(--text-muted);
}

/* ==========================================================================
   4. Contact Section
   ========================================================================== */
.contact-box {
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  padding: 48px;
  border-radius: 8px;
}

.contact-heading {
  font-size: 1.75rem;
  margin-bottom: 12px;
}

.contact-desc {
  color: var(--text-muted);
  margin-bottom: 36px;
}

.contact-links {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 16px;
}

.contact-card {
  padding: 20px;
  border: 1px solid var(--border-color);
  border-radius: 6px;
  background-color: var(--bg-color);
  display: flex;
  flex-direction: column;
  gap: 8px;
  transition: all var(--transition-fast);
}

.contact-card:hover {
  border-color: var(--accent);
  transform: translateY(-3px);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.03);
}

.contact-card-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.contact-type {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--text-light);
  text-transform: uppercase;
}

.contact-arrow {
  font-size: 0.9rem;
  color: var(--accent);
}

.contact-val {
  font-family: var(--font-mono);
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--text-main);
}

/* ==========================================================================
   Footer
   ========================================================================== */
.footer {
  padding: 40px 0;
  border-top: 1px solid var(--border-color);
  font-size: 0.85rem;
  color: var(--text-light);
  font-family: var(--font-mono);
}

.footer-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 16px;
}

/* ==========================================================================
   Animations & Responsive
   ========================================================================== */
.fade-in {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s cubic-bezier(0.16, 1, 0.3, 1), transform 0.6s cubic-bezier(0.16, 1, 0.3, 1);
}

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

/* Accessibility: prefers-reduced-motion */
@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;
  }
  .fade-in {
    opacity: 1 !important;
    transform: none !important;
  }
}

/* Responsive adjustments */
@media (max-width: 768px) {
  .nav ul {
    gap: 16px;
  }

  .about-grid {
    grid-template-columns: 1fr;
    gap: 32px;
  }

  .timeline::before {
    left: 19px;
  }

  .timeline-item {
    flex-direction: column;
  }

  .timeline-meta {
    width: auto;
    text-align: left;
    padding-right: 0;
    padding-left: 36px;
    margin-bottom: 4px;
  }

  .timeline-marker {
    position: absolute;
    top: 6px;
    left: 14px;
  }

  .timeline-content {
    margin-left: 36px;
    width: calc(100% - 36px);
  }

  .contact-box {
    padding: 24px;
  }
}