/* ==========================================================================
   BASE STYLES, RESET & TYPOGRAPHY HIERARCHY
   ========================================================================== */

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

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
  font-size: 16px;
  overflow-x: hidden;
}

body {
  font-family: var(--font-body);
  font-size: var(--text-base);
  line-height: 1.65;
  color: var(--text-primary);
  background-color: var(--bg-primary);
  transition: var(--transition-theme);
  overflow-x: hidden;
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* Display & Editorial Headings */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-display);
  color: var(--text-primary);
  line-height: 1.12;
  font-weight: 700;
  letter-spacing: -0.03em;
  transition: color 240ms ease;
}

/* Italic Descender Clearance (Section 4.1 mandatory rule) */
h1 em, h2 em, h3 em, .display-italic {
  font-style: italic;
  line-height: 1.15;
  padding-bottom: 0.08em;
  display: inline-block;
}

h1 {
  font-size: clamp(2.35rem, 4.2vw + 1rem, 3.75rem);
  font-weight: 700;
  letter-spacing: -0.035em;
}

h2 {
  font-size: clamp(1.85rem, 3vw + 0.6rem, 2.75rem);
  letter-spacing: -0.03em;
}

h3 {
  font-size: clamp(1.25rem, 1.6vw + 0.5rem, 1.5rem);
  letter-spacing: -0.02em;
}

h4 {
  font-size: var(--text-lg);
}

p {
  color: var(--text-secondary);
  font-size: var(--text-base);
  line-height: 1.65;
  max-width: 65ch;
  transition: color 240ms ease;
}

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

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

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

button, input, textarea, select {
  font-family: inherit;
  font-size: inherit;
  color: inherit;
}

/* Accessibility Focus States */
:focus-visible {
  outline: 2px solid var(--border-focus);
  outline-offset: 3px;
  border-radius: var(--radius-btn);
}

/* Custom Scrollbar */
::-webkit-scrollbar {
  width: 8px;
}

::-webkit-scrollbar-track {
  background: var(--bg-primary);
}

::-webkit-scrollbar-thumb {
  background: var(--bg-surface-elevated);
  border-radius: var(--radius-btn);
}

::-webkit-scrollbar-thumb:hover {
  background: var(--accent);
}

::selection {
  background: var(--accent-subtle);
  color: var(--text-primary);
}

/* Container System (max-w-7xl / 1280px standard) */
.container {
  width: 100%;
  max-width: var(--container-xl);
  margin-left: auto;
  margin-right: auto;
  padding-left: var(--space-4);
  padding-right: var(--space-4);
}

@media (min-width: 640px) {
  .container {
    padding-left: var(--space-6);
    padding-right: var(--space-6);
  }
}

@media (min-width: 1024px) {
  .container {
    padding-left: var(--space-8);
    padding-right: var(--space-8);
  }
}

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

/* Section Spacing & Vertical Rhythm */
.section {
  position: relative;
  padding: var(--space-16) 0;
  scroll-margin-top: 4.5rem;
}

@media (min-width: 768px) {
  .section {
    padding: var(--space-24) 0;
  }
}

/* Vertical-Stacked Section Heading (Split-Header Ban compliant) */
.section-intro {
  max-width: 680px;
  margin-bottom: var(--space-12);
}

/* Rationed Eyebrow (Max 1 per 3 sections across the page) */
.eyebrow {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: var(--space-3);
}

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

.section-subtitle {
  font-size: var(--text-lg);
  color: var(--text-secondary);
  line-height: 1.6;
  max-width: 60ch;
}

/* Screen Reader & Honeypot Utility (modern-web-guidance compliant) */
.sr-only,
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  clip-path: inset(50%);
  white-space: nowrap;
  border: 0;
}

/* Motivated Scroll-Reveal (IntersectionObserver driven) */
@media (prefers-reduced-motion: no-preference) {
  .reveal {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.55s var(--ease-out-expo), transform 0.55s var(--ease-out-expo);
  }

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

  .reveal-delay-1 { transition-delay: 60ms; }
  .reveal-delay-2 { transition-delay: 120ms; }
  .reveal-delay-3 { transition-delay: 180ms; }
}

/* Mandatory Reduced Motion Guardrail (Section 6.B) */
@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;
  }

  .reveal {
    opacity: 1 !important;
    transform: none !important;
  }
}