/* ============================================
   LAYOUT SYSTEM — 45black.tech
   Grid, Flexbox, Containers, Responsive
   ============================================ */

/* ============================================
   RESET & BASE
   ============================================ */

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

html {
  font-size: 100%; /* 16px base */
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-sans);
  font-weight: var(--font-weight-normal);
  font-size: var(--font-size-base);
  line-height: var(--line-height-normal);
  color: var(--text-primary);
  background-color: var(--bg-paper);

  /* Fix IBM Plex Sans numeral alignment */
  font-feature-settings: 'tnum' 1, 'lnum' 1;
}

/* ============================================
   SEMANTIC HTML5 ELEMENTS
   ============================================ */

header[role="banner"] {
  position: sticky;
  top: 0;
  z-index: var(--z-sticky);
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(12px);
  border-bottom: var(--border-width-1) solid rgba(229, 231, 235, 0.8);
  box-shadow: var(--shadow-sm);
  transition: all var(--transition-base);
}

nav[role="navigation"] {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-md);
}

main {
  min-height: 60vh;
  padding: var(--space-2xl) 0;
}

footer[role="contentinfo"] {
  margin-top: var(--space-3xl);
  padding: var(--space-2xl) 0;
  background: linear-gradient(180deg, rgba(249, 250, 251, 0.5) 0%, rgba(243, 244, 246, 1) 100%);
  border-top: var(--border-width-1) solid rgba(229, 231, 235, 0.8);
  box-shadow: inset 0 1px 0 0 rgba(255, 255, 255, 0.5);
  font-size: var(--font-size-sm);
  color: var(--text-secondary);
}

/* ============================================
   CONTAINER SYSTEM
   ============================================ */

.container {
  width: 100%;
  max-width: var(--max-width-wide);
  margin-left: auto;
  margin-right: auto;
  padding-left: var(--space-md);
  padding-right: var(--space-md);
}

.container-narrow {
  max-width: var(--max-width-content);
}

.container-prose {
  max-width: var(--max-width-prose);
}

.container-reading {
  max-width: var(--max-width-reading);
}

.container-full {
  max-width: none;
  padding-left: 0;
  padding-right: 0;
}

/* ============================================
   SECTION LAYOUT
   ============================================ */

.section {
  position: relative;
  margin-bottom: var(--space-3xl);
  padding: var(--space-2xl) 0;
}

.section:last-child {
  margin-bottom: 0;
}

.section:nth-child(even) {
  background: linear-gradient(180deg, transparent 0%, rgba(249, 250, 251, 0.5) 50%, transparent 100%);
}

.section-compact {
  padding: var(--space-lg) 0;
}

.section-spacious {
  padding: var(--space-3xl) 0;
}

/* ============================================
   GRID SYSTEM
   ============================================ */

.grid {
  display: grid;
  gap: var(--space-md);
}

/* Responsive Grid Columns */
.grid-cols-1 {
  grid-template-columns: 1fr;
}

.grid-cols-2 {
  grid-template-columns: repeat(2, 1fr);
}

.grid-cols-3 {
  grid-template-columns: repeat(3, 1fr);
}

.grid-cols-4 {
  grid-template-columns: repeat(4, 1fr);
}

/* Auto-fit Grid (Responsive) */
.grid-auto-fit {
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 320px), 1fr));
}

.grid-auto-fill {
  grid-template-columns: repeat(auto-fill, minmax(min(100%, 320px), 1fr));
}

/* Gap Utilities */
.gap-xs { gap: var(--space-xs); }
.gap-sm { gap: var(--space-sm); }
.gap-md { gap: var(--space-md); }
.gap-lg { gap: var(--space-lg); }
.gap-xl { gap: var(--space-xl); }
.gap-2xl { gap: var(--space-2xl); }

/* ============================================
   FLEXBOX UTILITIES
   ============================================ */

.flex {
  display: flex;
}

.flex-row {
  flex-direction: row;
}

.flex-col {
  flex-direction: column;
}

.flex-wrap {
  flex-wrap: wrap;
}

.flex-nowrap {
  flex-wrap: nowrap;
}

/* Justify Content */
.justify-start { justify-content: flex-start; }
.justify-end { justify-content: flex-end; }
.justify-center { justify-content: center; }
.justify-between { justify-content: space-between; }
.justify-around { justify-content: space-around; }
.justify-evenly { justify-content: space-evenly; }

/* Align Items */
.items-start { align-items: flex-start; }
.items-end { align-items: flex-end; }
.items-center { align-items: center; }
.items-baseline { align-items: baseline; }
.items-stretch { align-items: stretch; }

/* Align Self */
.self-start { align-self: flex-start; }
.self-end { align-self: flex-end; }
.self-center { align-self: center; }
.self-baseline { align-self: baseline; }
.self-stretch { align-self: stretch; }

/* Flex Grow/Shrink */
.flex-1 { flex: 1 1 0%; }
.flex-auto { flex: 1 1 auto; }
.flex-initial { flex: 0 1 auto; }
.flex-none { flex: none; }

/* ============================================
   SPACING UTILITIES
   ============================================ */

/* Margin */
.m-0 { margin: 0; }
.m-auto { margin: auto; }

.mt-xs { margin-top: var(--space-xs); }
.mt-sm { margin-top: var(--space-sm); }
.mt-md { margin-top: var(--space-md); }
.mt-lg { margin-top: var(--space-lg); }
.mt-xl { margin-top: var(--space-xl); }
.mt-2xl { margin-top: var(--space-2xl); }
.mt-3xl { margin-top: var(--space-3xl); }

.mb-xs { margin-bottom: var(--space-xs); }
.mb-sm { margin-bottom: var(--space-sm); }
.mb-md { margin-bottom: var(--space-md); }
.mb-lg { margin-bottom: var(--space-lg); }
.mb-xl { margin-bottom: var(--space-xl); }
.mb-2xl { margin-bottom: var(--space-2xl); }
.mb-3xl { margin-bottom: var(--space-3xl); }

.ml-auto { margin-left: auto; }
.mr-auto { margin-right: auto; }
.mx-auto { margin-left: auto; margin-right: auto; }

/* Padding */
.p-0 { padding: 0; }

.px-xs { padding-left: var(--space-xs); padding-right: var(--space-xs); }
.px-sm { padding-left: var(--space-sm); padding-right: var(--space-sm); }
.px-md { padding-left: var(--space-md); padding-right: var(--space-md); }
.px-lg { padding-left: var(--space-lg); padding-right: var(--space-lg); }

.py-xs { padding-top: var(--space-xs); padding-bottom: var(--space-xs); }
.py-sm { padding-top: var(--space-sm); padding-bottom: var(--space-sm); }
.py-md { padding-top: var(--space-md); padding-bottom: var(--space-md); }
.py-lg { padding-top: var(--space-lg); padding-bottom: var(--space-lg); }
.py-xl { padding-top: var(--space-xl); padding-bottom: var(--space-xl); }
.py-2xl { padding-top: var(--space-2xl); padding-bottom: var(--space-2xl); }

/* ============================================
   RESPONSIVE LAYOUT (MOBILE FIRST)
   ============================================ */

/* Mobile: Default (320px - 767px) */
/* Styles above are mobile-first */

/* Tablet: 768px+ */
@media (min-width: 768px) {
  .container {
    padding-left: var(--space-lg);
    padding-right: var(--space-lg);
  }

  main {
    padding: var(--space-2xl) 0 var(--space-3xl) 0;
  }

  /* Tablet Grid Overrides */
  .md\:grid-cols-2 {
    grid-template-columns: repeat(2, 1fr);
  }

  .md\:grid-cols-3 {
    grid-template-columns: repeat(3, 1fr);
  }

  .md\:flex-row {
    flex-direction: row;
  }

  .md\:justify-between {
    justify-content: space-between;
  }
}

/* Desktop: 1024px+ */
@media (min-width: 1024px) {
  .container {
    padding-left: var(--space-xl);
    padding-right: var(--space-xl);
  }

  /* Desktop Grid Overrides */
  .lg\:grid-cols-3 {
    grid-template-columns: repeat(3, 1fr);
  }

  .lg\:grid-cols-4 {
    grid-template-columns: repeat(4, 1fr);
  }
}

/* Large Desktop: 1280px+ */
@media (min-width: 1280px) {
  /* Extra large layouts if needed */
}

/* ============================================
   ACCESSIBILITY
   ============================================ */

/* Skip to Content Link */
.skip-link {
  position: absolute;
  top: -999px;
  left: 0;
  padding: var(--space-sm) var(--space-md);
  background: var(--brand-primary);
  color: var(--text-on-dark);
  text-decoration: none;
  font-weight: var(--font-weight-semibold);
  z-index: var(--z-top);
  border-radius: var(--border-radius-base);
}

.skip-link:focus {
  top: var(--space-sm);
  left: var(--space-sm);
  outline: var(--focus-ring-width) var(--focus-ring-style) var(--focus-ring-color);
  outline-offset: var(--focus-ring-offset);
}

/* Screen Reader Only */
.sr-only,
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* ============================================
   PRINT STYLES
   ============================================ */

@media print {
  body {
    font-size: 12pt;
    color: #000;
    background: #fff;
  }

  header[role="banner"],
  nav[role="navigation"],
  .skip-link,
  .nav-toggle {
    display: none;
  }

  main {
    padding: 0;
  }

  a {
    text-decoration: underline;
    color: #000;
  }

  a[href^="http"]::after {
    content: " (" attr(href) ")";
    font-size: 0.8em;
    font-style: italic;
  }
}