/* ==========================================================================
   Oluwapelumi Ajanaku - Portfolio Stylesheet
   Pure Vanilla CSS3 • Mobile-First • Accessible • Self-Contained
   ========================================================================== */

/* --------------------------------------------------------------------------
   1. Design Tokens & CSS Custom Properties
   8px-based scale • Consistent Muted Neutrals • Single Cyan Accent
   -------------------------------------------------------------------------- */
:root {
  /* Color Palette - Neutrals */
  --bg-primary: #0a0d14;
  --bg-secondary: #111622;
  --bg-tertiary: #182030;
  --bg-elevated: #1e273b;

  --border-subtle: #1e283b;
  --border-default: #26334d;
  --border-focus: #38bdf8;

  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;

  /* Single Accent Color */
  --accent: #38bdf8;
  --accent-hover: #0ea5e9;
  --accent-surface: rgba(56, 189, 248, 0.08);
  --accent-border: rgba(56, 189, 248, 0.25);

  /* Typography */
  --font-system: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;

  /* Spacing Scale (8px rhythm) */
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-8: 32px;
  --space-10: 40px;
  --space-12: 48px;
  --space-16: 64px;
  --space-20: 80px;

  /* Layout */
  --container-max: 1120px;
  --header-height: 64px;
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-normal: 250ms ease;
}

/* --------------------------------------------------------------------------
   2. Reset & Baseline Setup
   -------------------------------------------------------------------------- */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-family: var(--font-system);
  font-size: 16px;
  line-height: 1.6;
  color: var(--text-primary);
  background-color: var(--bg-primary);
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  overflow-x: hidden;
}

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

a {
  color: inherit;
  text-decoration: none;
}

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

ul, ol {
  list-style: none;
}

/* --------------------------------------------------------------------------
   3. Accessibility & Focus Indicators
   -------------------------------------------------------------------------- */
:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

.skip-link {
  position: absolute;
  top: -60px;
  left: var(--space-4);
  background-color: var(--accent);
  color: var(--bg-primary);
  font-weight: 600;
  padding: var(--space-3) var(--space-4);
  border-radius: var(--radius-sm);
  z-index: 1000;
  transition: top var(--transition-fast);
}

.skip-link:focus {
  top: var(--space-4);
}

/* --------------------------------------------------------------------------
   4. Typography & Layout Utilities
   -------------------------------------------------------------------------- */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin-left: auto;
  margin-right: auto;
  padding-left: var(--space-4);
  padding-right: var(--space-4);
}

@media (min-width: 768px) {
  .container {
    padding-left: var(--space-8);
    padding-right: var(--space-8);
  }
}

.section {
  padding-top: var(--space-16);
  padding-bottom: var(--space-16);
  border-bottom: 1px solid var(--border-subtle);
}

@media (min-width: 768px) {
  .section {
    padding-top: var(--space-20);
    padding-bottom: var(--space-20);
  }
}

.section-header {
  max-width: 680px;
  margin-bottom: var(--space-12);
}

.section-title {
  font-size: clamp(1.6rem, 3vw, 2.25rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text-primary);
  line-height: 1.25;
  margin-bottom: var(--space-3);
}

.section-lead {
  font-size: clamp(1rem, 1.5vw, 1.125rem);
  color: var(--text-secondary);
  line-height: 1.6;
}

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

/* --------------------------------------------------------------------------
   5. Buttons & Badges
   -------------------------------------------------------------------------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  min-height: 44px;
  padding: var(--space-3) var(--space-6);
  font-size: 0.9375rem;
  font-weight: 600;
  border-radius: var(--radius-md);
  transition: background-color var(--transition-fast), border-color var(--transition-fast), color var(--transition-fast);
}

.btn svg {
  width: 18px;
  height: 18px;
  flex-shrink: 0;
}

.btn-primary {
  background-color: var(--accent);
  color: #07090e;
  border: 1px solid var(--accent);
}

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

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

.btn-secondary:hover {
  background-color: var(--bg-tertiary);
  border-color: var(--accent-border);
  color: var(--accent);
}

.btn-sm {
  min-height: 36px;
  padding: var(--space-2) var(--space-4);
  font-size: 0.875rem;
}

/* --------------------------------------------------------------------------
   6. Site Header & Navigation
   -------------------------------------------------------------------------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: rgba(10, 13, 20, 0.92);
  border-bottom: 1px solid var(--border-subtle);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
}

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

.brand-link {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-weight: 700;
  font-size: 1.05rem;
  color: var(--text-primary);
}

.brand-monogram {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  background-color: var(--accent-surface);
  border: 1px solid var(--accent-border);
  color: var(--accent);
  border-radius: var(--radius-sm);
  font-size: 0.875rem;
  font-weight: 700;
}

.brand-name {
  letter-spacing: -0.01em;
}

/* Desktop Navigation */
.nav-desktop {
  display: none;
  align-items: center;
  gap: var(--space-6);
}

.nav-link {
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--text-secondary);
  padding: var(--space-2) var(--space-1);
  border-bottom: 2px solid transparent;
  transition: color var(--transition-fast), border-color var(--transition-fast);
}

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

.nav-link.active {
  color: var(--accent);
  border-bottom-color: var(--accent);
}

/* Mobile Navigation Toggle Button */
.mobile-nav-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border-radius: var(--radius-md);
  color: var(--text-primary);
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-default);
}

.hamburger-icon {
  width: 20px;
  height: 20px;
}

/* Mobile Drawer */
.mobile-nav-menu {
  display: flex;
  flex-direction: column;
  padding: var(--space-4);
  background-color: var(--bg-secondary);
  border-bottom: 1px solid var(--border-default);
  gap: var(--space-2);
}

.mobile-nav-menu[hidden] {
  display: none;
}

.mobile-nav-link {
  display: flex;
  align-items: center;
  min-height: 44px;
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-weight: 500;
  color: var(--text-secondary);
}

.mobile-nav-link:hover,
.mobile-nav-link.active {
  color: var(--accent);
  background-color: var(--bg-tertiary);
}

@media (min-width: 768px) {
  .nav-desktop {
    display: flex;
  }

  .mobile-nav-toggle,
  .mobile-nav-menu {
    display: none !important;
  }
}

/* --------------------------------------------------------------------------
   7. Hero Section
   -------------------------------------------------------------------------- */
.hero-section {
  padding-top: clamp(var(--space-12), 8vw, var(--space-20));
  padding-bottom: clamp(var(--space-12), 8vw, var(--space-20));
}

.hero-content {
  max-width: 740px;
}

.hero-title {
  font-size: clamp(2.25rem, 5vw, 3.75rem);
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1.15;
  margin-bottom: var(--space-3);
  color: var(--text-primary);
}

.hero-role {
  font-size: clamp(1.125rem, 2vw, 1.375rem);
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: var(--space-5);
  letter-spacing: -0.01em;
}

.hero-value-prop {
  font-size: clamp(1rem, 1.5vw, 1.125rem);
  color: var(--text-secondary);
  line-height: 1.7;
  margin-bottom: var(--space-8);
  max-width: 640px;
}

.hero-ctas {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-4);
}

/* --------------------------------------------------------------------------
   8. About & Engineering Philosophy
   -------------------------------------------------------------------------- */
.philosophy-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-4);
}

@media (min-width: 640px) {
  .philosophy-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1024px) {
  .philosophy-grid {
    grid-template-columns: repeat(3, 1fr);
  }

  .philosophy-card-wide {
    grid-column: span 3;
  }
}

.philosophy-card {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: var(--space-6);
  transition: border-color var(--transition-fast);
}

.philosophy-card:hover {
  border-color: var(--border-default);
}

.philosophy-title {
  font-size: 1.125rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: var(--space-3);
  letter-spacing: -0.01em;
}

.philosophy-text {
  font-size: 0.9375rem;
  color: var(--text-secondary);
  line-height: 1.65;
}

/* --------------------------------------------------------------------------
   9. Technical Skills Section
   -------------------------------------------------------------------------- */
.skills-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-4);
}

@media (min-width: 640px) {
  .skills-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1024px) {
  .skills-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

.skills-card {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: var(--space-6);
}

.skills-group-title {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: var(--space-4);
  padding-bottom: var(--space-2);
  border-bottom: 1px solid var(--border-subtle);
}

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

.skill-tag {
  display: inline-flex;
  align-items: center;
  min-height: 32px;
  padding: var(--space-1) var(--space-3);
  background-color: var(--bg-tertiary);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-sm);
  font-size: 0.875rem;
  color: var(--text-primary);
  font-weight: 500;
}

/* --------------------------------------------------------------------------
   10. Featured Projects Section
   -------------------------------------------------------------------------- */
.projects-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-8);
}

.project-card {
  display: grid;
  grid-template-columns: 1fr;
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: border-color var(--transition-fast), transform var(--transition-fast), opacity 0.5s ease;
  opacity: 1;
}

.project-card:hover {
  border-color: var(--border-default);
}

/* Subtle intersection observer fade-in */
.project-card.will-fade {
  opacity: 0;
  transform: translateY(16px);
}

.project-card.is-visible {
  opacity: 1;
  transform: translateY(0);
}

@media (min-width: 900px) {
  .project-card {
    grid-template-columns: 42% 58%;
  }
}

.project-visual {
  background-color: var(--bg-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-4);
  border-bottom: 1px solid var(--border-subtle);
}

@media (min-width: 900px) {
  .project-visual {
    border-bottom: none;
    border-right: 1px solid var(--border-subtle);
  }
}

.project-illustration {
  width: 100%;
  height: auto;
  border-radius: var(--radius-sm);
}

.project-details {
  padding: var(--space-6);
  display: flex;
  flex-direction: column;
}

@media (min-width: 768px) {
  .project-details {
    padding: var(--space-8);
  }
}

.project-badge-notice {
  align-self: flex-start;
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--accent);
  background-color: var(--accent-surface);
  border: 1px solid var(--accent-border);
  padding: var(--space-1) var(--space-2);
  border-radius: var(--radius-sm);
  margin-bottom: var(--space-2);
}

.project-title {
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: var(--space-2);
  letter-spacing: -0.01em;
}

.project-description {
  font-size: 0.9375rem;
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: var(--space-4);
}

.project-tech-stack {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin-bottom: var(--space-4);
}

.tech-badge {
  font-size: 0.8125rem;
  font-weight: 600;
  padding: 2px var(--space-2);
  background-color: var(--bg-tertiary);
  border: 1px solid var(--border-default);
  color: var(--accent);
  border-radius: var(--radius-sm);
}

.project-highlights {
  list-style: disc;
  padding-left: var(--space-5);
  margin-bottom: var(--space-6);
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.project-highlights li {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.55;
}

.project-highlights code {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  color: var(--text-primary);
  background-color: var(--bg-tertiary);
  padding: 1px 4px;
  border-radius: var(--radius-sm);
}

.project-actions {
  margin-top: auto;
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
}

/* --------------------------------------------------------------------------
   11. Contact Section
   -------------------------------------------------------------------------- */
.contact-container {
  max-width: 800px;
}

.contact-methods {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-4);
}

@media (min-width: 600px) {
  .contact-methods {
    grid-template-columns: repeat(2, 1fr);
  }
}

.contact-card {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  padding: var(--space-5);
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  min-height: 72px;
  transition: border-color var(--transition-fast), background-color var(--transition-fast);
}

.contact-card:hover {
  background-color: var(--bg-tertiary);
  border-color: var(--accent-border);
}

.contact-icon {
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: var(--accent-surface);
  color: var(--accent);
  border-radius: var(--radius-md);
  flex-shrink: 0;
}

.contact-icon svg {
  width: 22px;
  height: 22px;
}

.contact-info {
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.contact-label {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  font-weight: 600;
  margin-bottom: 2px;
}

.contact-value {
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--text-primary);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

/* --------------------------------------------------------------------------
   12. Site Footer
   -------------------------------------------------------------------------- */
.site-footer {
  padding-top: var(--space-8);
  padding-bottom: var(--space-8);
  background-color: var(--bg-primary);
}

.footer-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  text-align: center;
}

@media (min-width: 600px) {
  .footer-container {
    flex-direction: row;
    text-align: left;
  }
}

.footer-copy {
  font-size: 0.875rem;
  color: var(--text-muted);
}

.back-to-top {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  min-height: 44px;
  padding: 0 var(--space-2);
  transition: color var(--transition-fast);
}

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

.back-to-top svg {
  width: 16px;
  height: 16px;
}

/* --------------------------------------------------------------------------
   13. Reduced Motion Media Query (MANDATORY)
   -------------------------------------------------------------------------- */
@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }

  .project-card.will-fade {
    opacity: 1 !important;
    transform: none !important;
  }
}