/* ==========================================================================
   Main CSS - Base, Typography, Layout, & Accessibility
   Data Centre Academy Asia (DCAA)
   ========================================================================== */

/* Modern CSS Reset */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  line-height: var(--line-height-normal);
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  color-scheme: light;
  overflow-x: clip;
}

body {
  font-family: var(--font-family-sans);
  color: var(--color-text-primary);
  background-color: var(--color-bg-base);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  overflow-x: clip;
  max-width: 100%;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* Skip to Content Accessible Link */
.skip-link {
  position: absolute;
  top: -100px;
  left: var(--space-4);
  background: var(--color-brand-accent);
  color: #FFFFFF;
  padding: var(--space-3) var(--space-6);
  border-radius: var(--radius-sm);
  font-weight: var(--font-weight-semibold);
  font-size: var(--font-size-sm);
  z-index: 9999;
  text-decoration: none;
  transition: top var(--transition-fast);
}

.skip-link:focus {
  top: var(--space-4);
  outline: 3px solid #FFFFFF;
  outline-offset: 2px;
}

/* Universal Focus States */
:focus-visible {
  outline: 2px solid var(--color-border-focus);
  outline-offset: 2px;
}

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

/* Typography Hierarchy */
h1, h2, h3, h4, h5, h6 {
  color: var(--color-text-primary);
  font-family: var(--font-family-sans);
  font-weight: var(--font-weight-bold);
  line-height: var(--line-height-tight);
  letter-spacing: -0.015em;
}

h1 {
  font-size: var(--font-size-4xl);
  margin-bottom: var(--space-6);
}

h2 {
  font-size: var(--font-size-3xl);
  margin-bottom: var(--space-4);
}

h3 {
  font-size: var(--font-size-2xl);
  margin-bottom: var(--space-3);
  font-weight: var(--font-weight-semibold);
}

h4 {
  font-size: var(--font-size-xl);
  margin-bottom: var(--space-2);
  font-weight: var(--font-weight-semibold);
}

p {
  color: var(--color-text-secondary);
  font-size: var(--font-size-base);
  line-height: var(--line-height-relaxed);
  margin-bottom: var(--space-4);
}

p:last-child {
  margin-bottom: 0;
}

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

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

ul, ol {
  list-style: none;
}

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

/* Container & Section Layouts */
.container {
  width: 100%;
  max-width: var(--container-max-width);
  margin-left: auto;
  margin-right: auto;
  padding-left: var(--container-padding);
  padding-right: var(--container-padding);
}

.section {
  padding-top: var(--space-16);
  padding-bottom: var(--space-16);
}

.section--subtle {
  background-color: var(--color-bg-subtle);
  border-top: 1px solid var(--color-border-subtle);
  border-bottom: 1px solid var(--color-border-subtle);
}

.section--dark {
  background-color: var(--color-brand-dark);
  color: var(--color-text-inverse);
  border-top: 1px solid var(--color-border-dark);
  border-bottom: 1px solid var(--color-border-dark);
}

.section--dark h2,
.section--dark h3,
.section--dark h4 {
  color: var(--color-text-inverse);
}

.section--dark p {
  color: var(--color-text-inverse-muted);
}

/* Section Header Component */
.section-header {
  margin-bottom: var(--space-12);
  max-width: 760px;
}

.section-header--center {
  margin-left: auto;
  margin-right: auto;
  text-align: center;
}

.section-header__tag {
  display: inline-block;
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-semibold);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-brand-accent);
  margin-bottom: var(--space-2);
}

.section-header__title {
  margin-bottom: var(--space-4);
}

.section-header__description {
  font-size: var(--font-size-lg);
  line-height: var(--line-height-normal);
  color: var(--color-text-secondary);
}

/* Grid Utilities */
.grid {
  display: grid;
  gap: var(--space-6);
}

.grid > * {
  min-width: 0;
}

.grid--2 {
  grid-template-columns: 1fr;
}

.grid--3 {
  grid-template-columns: 1fr;
}

.grid--4 {
  grid-template-columns: 1fr;
}

@media (min-width: 640px) {
  :root {
    --container-padding: var(--space-6);
  }
  .grid--2 {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 768px) {
  .grid--3 {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1024px) {
  .grid--3 {
    grid-template-columns: repeat(3, 1fr);
  }
  .grid--4 {
    grid-template-columns: repeat(4, 1fr);
  }
}

/* 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;
  }
}

/* Desktop Typographic Enhancements */
@media (min-width: 768px) {
  h1 {
    font-size: var(--font-size-5xl);
  }
  h2 {
    font-size: var(--font-size-4xl);
  }
  .section {
    padding-top: var(--space-20);
    padding-bottom: var(--space-20);
  }
}

@media (min-width: 1024px) {
  .section {
    padding-top: var(--space-24);
    padding-bottom: var(--space-24);
  }
}

/* --------------------------------------------------------------------------
   Architectural & Blueprint Utilities
   -------------------------------------------------------------------------- */
.bg-grid-dark {
  background-color: var(--color-brand-navy-950);
  background-image: 
    linear-gradient(to right, rgba(255, 255, 255, 0.03) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(255, 255, 255, 0.03) 1px, transparent 1px);
  background-size: 48px 48px;
}

.bg-grid-subtle {
  background-color: var(--color-bg-warm);
  background-image: 
    linear-gradient(to right, rgba(15, 23, 42, 0.03) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(15, 23, 42, 0.03) 1px, transparent 1px);
  background-size: 40px 40px;
}

.mono-tag {
  font-family: var(--font-family-mono);
  font-size: var(--font-size-xs);
  letter-spacing: var(--letter-spacing-mono);
  text-transform: uppercase;
  color: var(--color-brand-accent-bright);
}

.hairline-top {
  border-top: 1px solid var(--color-border-dark-hairline);
}

.hairline-bottom {
  border-bottom: 1px solid var(--color-border-dark-hairline);
}