/* ==========================================================================
   NADIMPALLY NAGA SHANKAR - PRINCIPAL SYSTEMS ARCHITECT PORTFOLIO
   Design System & Styling
   Built for Clarity, Low-Latency Visual Hierarchy & Strict Accessibility
   ========================================================================== */

/* --------------------------------------------------------------------------
   1. Design Tokens & CSS Custom Properties
   -------------------------------------------------------------------------- */
:root {
  /* Color Palette - Sovereign Obsidian & Signal Emerald Theme */
  --bg-base: #0B0F14;          /* Bare-metal dark obsidian background */
  --bg-surface: #121820;       /* Dark slate surface layer */
  --bg-surface-hover: #1A232F; /* Elevated hover surface */
  --bg-subtle: #17202B;        /* Subtle container backdrop */
  
  --border-muted: #212B38;     /* 1px clean architectural border */
  --border-active: #00E5A3;    /* Active state / focus accent border */
  
  --text-primary: #F0F4F8;     /* High contrast text (Contrast > 14:1) */
  --text-secondary: #94A3B8;   /* Muted steel gray secondary text (Contrast > 5.2:1) */
  --text-tertiary: #64748B;    /* De-emphasized labels */
  --text-inverse: #0B0F14;     /* Dark text on light accent fills */
  
  --accent-primary: #00E5A3;   /* Signal Emerald - primary interactions & status */
  --accent-primary-hover: #00C78E;
  --accent-muted: rgba(0, 229, 163, 0.12);
  --accent-alert: #FF6B4A;     /* Crisis Alert Red */

  /* Typography */
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  
  /* Type Hierarchy (Restrained: 3 Main Sizes) */
  --text-size-lg: 1.875rem;    /* 30px - Primary Page / Section Titles */
  --text-size-md: 1.25rem;     /* 20px - Subheadings & Metric Labels */
  --text-size-sm: 0.9375rem;   /* 15px - Body text & Spec detail */
  --text-size-xs: 0.8125rem;   /* 13px - Micro metadata & tags */

  /* Spacing Scale (8px Grid) */
  --space-xs: 0.5rem;    /* 8px */
  --space-sm: 1rem;      /* 16px */
  --space-md: 1.5rem;    /* 24px */
  --space-lg: 2rem;      /* 32px */
  --space-xl: 3rem;      /* 48px */
  --space-2xl: 4rem;     /* 64px */

  /* Layout & Controls */
  --container-max-width: 1140px;
  --radius-sm: 2px;
  --radius-md: 4px;
  --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.6;
  background-color: var(--bg-base);
  color: var(--text-primary);
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Accessible Focus States */
:focus-visible {
  outline: 2px solid var(--accent-primary);
  outline-offset: 3px;
}

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

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

/* Skip link for screen reader accessibility */
.skip-link {
  position: absolute;
  top: -100px;
  left: 1rem;
  background: var(--accent-primary);
  color: var(--text-inverse);
  padding: 0.5rem 1rem;
  font-weight: 600;
  z-index: 1000;
  transition: top var(--transition-fast);
}

.skip-link:focus {
  top: 1rem;
}

/* --------------------------------------------------------------------------
   3. Layout Structure
   -------------------------------------------------------------------------- */
.container {
  width: 100%;
  max-width: var(--container-max-width);
  margin: 0 auto;
  padding: 0 var(--space-sm);
}

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

.section {
  padding: var(--space-xl) 0;
  border-bottom: 1px solid var(--border-muted);
}

.section:last-of-type {
  border-bottom: none;
}

/* Section Header Typography */
.section-title {
  font-family: var(--font-mono);
  font-size: var(--text-size-lg);
  font-weight: 600;
  letter-spacing: -0.02em;
  color: var(--text-primary);
  margin-bottom: var(--space-xs);
  display: flex;
  align-items: center;
  gap: var(--space-xs);
}

.section-title::before {
  content: "//";
  color: var(--accent-primary);
  font-weight: 700;
}

.section-subtitle {
  font-size: var(--text-size-sm);
  color: var(--text-secondary);
  margin-bottom: var(--space-md);
  max-width: 780px;
}

/* --------------------------------------------------------------------------
   4. Header & Identity Section
   -------------------------------------------------------------------------- */
.site-header {
  border-bottom: 1px solid var(--border-muted);
  background-color: var(--bg-surface);
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 64px;
}

.brand-id {
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: 1rem;
  letter-spacing: -0.01em;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.brand-tag {
  font-size: var(--text-size-xs);
  color: var(--accent-primary);
  background-color: var(--accent-muted);
  padding: 2px 6px;
  border-radius: var(--radius-sm);
  font-weight: 500;
}

.nav-links {
  display: flex;
  gap: var(--space-md);
  list-style: none;
}

.nav-link {
  font-family: var(--font-mono);
  font-size: var(--text-size-xs);
  color: var(--text-secondary);
  transition: color var(--transition-fast);
  padding: 4px 0;
}

.nav-link:hover, .nav-link:focus {
  color: var(--accent-primary);
}

/* Hero / Identity Banner */
.hero-block {
  padding: var(--space-xl) 0 var(--space-lg);
  border-bottom: 1px solid var(--border-muted);
}

.status-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-family: var(--font-mono);
  font-size: var(--text-size-xs);
  color: var(--accent-primary);
  background-color: var(--bg-surface);
  border: 1px solid var(--border-muted);
  padding: 0.35rem 0.75rem;
  border-radius: var(--radius-sm);
  margin-bottom: var(--space-md);
}

.status-dot {
  width: 8px;
  height: 8px;
  background-color: var(--accent-primary);
  border-radius: 50%;
  display: inline-block;
  box-shadow: 0 0 8px rgba(0, 229, 163, 0.4);
}

.hero-title {
  font-family: var(--font-sans);
  font-size: 2.5rem;
  font-weight: 700;
  line-height: 1.15;
  color: var(--text-primary);
  margin-bottom: var(--space-xs);
  letter-spacing: -0.03em;
}

@media (min-width: 768px) {
  .hero-title {
    font-size: 3.25rem;
  }
}

.hero-role {
  font-family: var(--font-mono);
  font-size: var(--text-size-md);
  color: var(--accent-primary);
  margin-bottom: var(--space-md);
  font-weight: 500;
}

.hero-meta-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-sm);
  background-color: var(--bg-surface);
  border: 1px solid var(--border-muted);
  padding: var(--space-md);
  border-radius: var(--radius-md);
  margin-bottom: var(--space-md);
}

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

.meta-item {
  display: flex;
  flex-direction: column;
}

.meta-label {
  font-family: var(--font-mono);
  font-size: var(--text-size-xs);
  color: var(--text-tertiary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 2px;
}

.meta-value {
  font-size: var(--text-size-sm);
  color: var(--text-primary);
  font-weight: 500;
}

.summary-text {
  font-size: var(--text-size-sm);
  color: var(--text-secondary);
  line-height: 1.7;
  max-width: 900px;
}

.action-bar {
  margin-top: var(--space-md);
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
}

.btn-primary {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background-color: var(--accent-primary);
  color: var(--text-inverse);
  font-family: var(--font-mono);
  font-size: var(--text-size-xs);
  font-weight: 700;
  padding: 0.75rem 1.25rem;
  border-radius: var(--radius-sm);
  transition: background-color var(--transition-fast), transform var(--transition-fast);
}

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

.btn-secondary {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background-color: var(--bg-surface);
  color: var(--text-primary);
  border: 1px solid var(--border-muted);
  font-family: var(--font-mono);
  font-size: var(--text-size-xs);
  font-weight: 600;
  padding: 0.75rem 1.25rem;
  border-radius: var(--radius-sm);
  transition: border-color var(--transition-fast), background-color var(--transition-fast);
}

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

/* --------------------------------------------------------------------------
   5. Core Competencies Grid & Search Filter
   -------------------------------------------------------------------------- */
.filter-bar {
  display: flex;
  gap: var(--space-xs);
  margin-bottom: var(--space-md);
  flex-wrap: wrap;
}

.filter-btn {
  font-family: var(--font-mono);
  font-size: var(--text-size-xs);
  color: var(--text-secondary);
  background-color: var(--bg-surface);
  border: 1px solid var(--border-muted);
  padding: 0.4rem 0.8rem;
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
}

.filter-btn:hover {
  color: var(--text-primary);
  border-color: var(--text-secondary);
}

.filter-btn.active {
  color: var(--text-inverse);
  background-color: var(--accent-primary);
  border-color: var(--accent-primary);
  font-weight: 600;
}

.competencies-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-sm);
}

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

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

.competency-card {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-muted);
  padding: var(--space-md);
  border-radius: var(--radius-md);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  transition: border-color var(--transition-fast);
}

.competency-card:hover {
  border-color: var(--border-active);
}

.competency-title {
  font-family: var(--font-mono);
  font-size: var(--text-size-sm);
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: var(--space-xs);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.competency-desc {
  font-size: var(--text-size-xs);
  color: var(--text-secondary);
  line-height: 1.5;
}

/* --------------------------------------------------------------------------
   6. High-Stakes Narrative Projects
   -------------------------------------------------------------------------- */
.projects-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-lg);
}

.project-entry {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-muted);
  border-left: 3px solid var(--accent-primary);
  padding: var(--space-md);
  border-radius: var(--radius-md);
}

.project-header {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  margin-bottom: var(--space-sm);
}

@media (min-width: 768px) {
  .project-header {
    flex-direction: row;
    justify-content: space-between;
    align-items: baseline;
  }
}

.project-name {
  font-family: var(--font-mono);
  font-size: var(--text-size-md);
  font-weight: 600;
  color: var(--text-primary);
}

.project-metrics-badge {
  font-family: var(--font-mono);
  font-size: var(--text-size-xs);
  color: var(--accent-primary);
  background-color: var(--accent-muted);
  padding: 2px 8px;
  border-radius: var(--radius-sm);
  align-self: flex-start;
  font-weight: 600;
}

.project-body {
  font-size: var(--text-size-sm);
  color: var(--text-secondary);
  line-height: 1.65;
}

.project-highlights {
  margin-top: var(--space-sm);
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.highlight-tag {
  font-family: var(--font-mono);
  font-size: var(--text-size-xs);
  color: var(--text-tertiary);
  background-color: var(--bg-base);
  border: 1px solid var(--border-muted);
  padding: 2px 6px;
  border-radius: var(--radius-sm);
}

/* --------------------------------------------------------------------------
   7. Technical Stack Matrix
   -------------------------------------------------------------------------- */
.stack-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-md);
}

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

.stack-category {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-muted);
  padding: var(--space-md);
  border-radius: var(--radius-md);
}

.stack-category-name {
  font-family: var(--font-mono);
  font-size: var(--text-size-sm);
  font-weight: 600;
  color: var(--accent-primary);
  margin-bottom: var(--space-xs);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.stack-items-list {
  font-size: var(--text-size-sm);
  color: var(--text-secondary);
  line-height: 1.6;
}

/* --------------------------------------------------------------------------
   8. Education & Track Record
   -------------------------------------------------------------------------- */
.mastery-block {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-muted);
  padding: var(--space-md);
  border-radius: var(--radius-md);
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.mastery-item-title {
  font-family: var(--font-mono);
  font-size: var(--text-size-sm);
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 4px;
}

.mastery-item-desc {
  font-size: var(--text-size-sm);
  color: var(--text-secondary);
}

/* --------------------------------------------------------------------------
   9. Sovereign Inquiry & Direct Contact Modal Overlay
   -------------------------------------------------------------------------- */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  background-color: rgba(11, 15, 20, 0.85);
  backdrop-filter: blur(4px);
  display: flex;
  justify-content: center;
  align-items: center;
  z-index: 1000;
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--transition-fast);
  padding: var(--space-sm);
}

.modal-overlay.active {
  opacity: 1;
  pointer-events: auto;
}

.modal-content {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-muted);
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.5);
  border-radius: var(--radius-md);
  width: 100%;
  max-width: 600px;
  padding: var(--space-lg);
  position: relative;
}

.modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--space-md);
  border-bottom: 1px solid var(--border-muted);
  padding-bottom: var(--space-xs);
}

.modal-title {
  font-family: var(--font-mono);
  font-size: var(--text-size-md);
  font-weight: 600;
  color: var(--text-primary);
}

.modal-close {
  font-family: var(--font-mono);
  font-size: var(--text-size-md);
  color: var(--text-secondary);
  padding: 4px 8px;
}

.modal-close:hover {
  color: var(--accent-primary);
}

.modal-body {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.form-label {
  font-family: var(--font-mono);
  font-size: var(--text-size-xs);
  color: var(--text-tertiary);
  text-transform: uppercase;
}

.form-input, .form-textarea {
  background-color: var(--bg-base);
  border: 1px solid var(--border-muted);
  color: var(--text-primary);
  font-family: var(--font-mono);
  font-size: var(--text-size-sm);
  padding: 0.6rem 0.75rem;
  border-radius: var(--radius-sm);
  transition: border-color var(--transition-fast);
}

.form-input:focus, .form-textarea:focus {
  border-color: var(--accent-primary);
  outline: none;
}

.pgp-box {
  background-color: var(--bg-base);
  border: 1px solid var(--border-muted);
  padding: var(--space-xs) var(--space-sm);
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  font-size: var(--text-size-xs);
  color: var(--text-secondary);
  display: flex;
  justify-content: space-between;
  align-items: center;
  word-break: break-all;
}

/* --------------------------------------------------------------------------
   10. Footer
   -------------------------------------------------------------------------- */
.site-footer {
  margin-top: auto;
  padding: var(--space-lg) 0;
  border-top: 1px solid var(--border-muted);
  background-color: var(--bg-surface);
  font-family: var(--font-mono);
  font-size: var(--text-size-xs);
  color: var(--text-tertiary);
}

.footer-content {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

@media (min-width: 768px) {
  .footer-content {
    flex-direction: row;
    justify-content: space-between;
    align-items: center;
  }
}

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