/* ==========================================================================
   DESIGN SYSTEM & CORE STYLES - SHIVA SAI SURISETTY PORTFOLIO
   Aesthetic: Linear / Vercel dark-first technical polish with subtle cyber glow
   ========================================================================== */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&family=JetBrains+Mono:wght@400;500;600&family=Outfit:wght@500;600;700;800&display=swap');

:root {
  /* Color Palette - Refined Obsidian & Electric Indigo/Cyan */
  --bg-primary: #08090d;
  --bg-secondary: #0f1117;
  --bg-tertiary: #161922;
  --bg-card: rgba(18, 21, 30, 0.75);
  --bg-card-hover: rgba(26, 31, 44, 0.85);
  --bg-glass: rgba(12, 14, 20, 0.7);
  --bg-input: rgba(15, 18, 26, 0.9);

  /* Borders & Dividers */
  --border-subtle: rgba(255, 255, 255, 0.07);
  --border-medium: rgba(255, 255, 255, 0.12);
  --border-accent: rgba(99, 102, 241, 0.35);
  --border-cyan: rgba(6, 182, 212, 0.35);

  /* Accents & Brand Colors */
  --accent-primary: #6366f1;       /* Indigo */
  --accent-primary-hover: #4f46e5;
  --accent-secondary: #06b6d4;     /* Cyan */
  --accent-emerald: #10b981;       /* Success / Online */
  --accent-amber: #f59e0b;         /* Warning / Highlight */
  --accent-rose: #f43f5e;          /* Red / Alert */
  --accent-purple: #a855f7;

  /* Gradients */
  --gradient-accent: linear-gradient(135deg, #6366f1 0%, #06b6d4 100%);
  --gradient-glow: linear-gradient(135deg, rgba(99, 102, 241, 0.15) 0%, rgba(6, 182, 212, 0.15) 100%);
  --gradient-card: linear-gradient(180deg, rgba(255, 255, 255, 0.03) 0%, rgba(255, 255, 255, 0) 100%);
  --gradient-text: linear-gradient(180deg, #ffffff 0%, #cbd5e1 100%);
  --gradient-heading: linear-gradient(135deg, #ffffff 30%, #94a3b8 100%);

  /* Text Colors */
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --text-inverse: #030712;

  /* Typography */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-heading: 'Outfit', 'Inter', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;

  /* Shadows & Glows */
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.35);
  --shadow-md: 0 8px 24px -4px rgba(0, 0, 0, 0.45);
  --shadow-lg: 0 20px 40px -10px rgba(0, 0, 0, 0.6);
  --shadow-glow: 0 0 25px rgba(99, 102, 241, 0.2);
  --shadow-glow-cyan: 0 0 25px rgba(6, 182, 212, 0.2);

  /* Layout & Spacing */
  --max-width: 1200px;
  --header-height: 72px;
  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 20px;
  --radius-full: 9999px;

  /* Transitions */
  --transition-fast: 150ms cubic-bezier(0.16, 1, 0.3, 1);
  --transition-normal: 250ms cubic-bezier(0.16, 1, 0.3, 1);
  --transition-slow: 400ms cubic-bezier(0.16, 1, 0.3, 1);
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-height) + 24px);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
}

body {
  min-height: 100vh;
  position: relative;
  overflow-x: hidden;
  background-color: var(--bg-primary);
  color: var(--text-primary);
}

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

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

::-webkit-scrollbar-thumb {
  background: var(--border-medium);
  border-radius: 4px;
}

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

::selection {
  background: rgba(99, 102, 241, 0.35);
  color: #ffffff;
}

/* Background Canvas */
#bg-canvas {
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  z-index: 0;
  pointer-events: none;
  opacity: 0.65;
}

/* Ambient Radial Glow Overlays */
.ambient-glow {
  position: fixed;
  border-radius: 50%;
  filter: blur(140px);
  pointer-events: none;
  z-index: 0;
  opacity: 0.18;
}

.ambient-glow-1 {
  top: -10%;
  left: 15%;
  width: 600px;
  height: 600px;
  background: var(--accent-primary);
}

.ambient-glow-2 {
  top: 45%;
  right: -5%;
  width: 500px;
  height: 500px;
  background: var(--accent-secondary);
}

.ambient-glow-3 {
  bottom: 5%;
  left: 10%;
  width: 450px;
  height: 450px;
  background: var(--accent-purple);
}

/* Typography Utilities */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  color: var(--text-primary);
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: -0.025em;
}

p {
  color: var(--text-secondary);
}

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

code, pre, .mono {
  font-family: var(--font-mono);
}

/* Section Containers */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
  position: relative;
  z-index: 1;
}

.section {
  padding: 100px 0;
  position: relative;
  z-index: 1;
}

.section-header {
  margin-bottom: 56px;
}

.section-header.text-center {
  text-align: center;
  max-width: 720px;
  margin-left: auto;
  margin-right: auto;
}

.section-tag {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 6px 14px;
  border-radius: var(--radius-full);
  background: rgba(99, 102, 241, 0.1);
  border: 1px solid var(--border-accent);
  color: var(--accent-primary);
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  font-weight: 500;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  margin-bottom: 16px;
}

.section-tag.cyan {
  background: rgba(6, 182, 212, 0.1);
  border-color: var(--border-cyan);
  color: var(--accent-secondary);
}

.section-tag.emerald {
  background: rgba(16, 185, 129, 0.1);
  border-color: rgba(16, 185, 129, 0.35);
  color: var(--accent-emerald);
}

.section-title {
  font-size: clamp(2rem, 4vw, 2.75rem);
  font-weight: 800;
  background: var(--gradient-heading);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  margin-bottom: 16px;
}

.section-description {
  font-size: 1.125rem;
  color: var(--text-secondary);
  line-height: 1.7;
}

/* Scroll Progress Bar */
.scroll-progress-bar {
  position: fixed;
  top: 0;
  left: 0;
  height: 3px;
  width: 0%;
  background: var(--gradient-accent);
  z-index: 9999;
  box-shadow: 0 0 10px rgba(99, 102, 241, 0.7);
  transition: width 50ms ease-out;
}

/* Grid & Layout Utilities */
.grid {
  display: grid;
  gap: 24px;
}

.flex {
  display: flex;
}

.flex-center {
  display: flex;
  align-items: center;
  justify-content: center;
}

.flex-between {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

/* Glass Card Baseline */
.glass-card {
  background: var(--bg-card);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  position: relative;
  overflow: hidden;
  transition: transform var(--transition-normal), border-color var(--transition-normal), box-shadow var(--transition-normal);
}

.glass-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.12), transparent);
  opacity: 0.7;
}

.glass-card:hover {
  border-color: var(--border-medium);
  box-shadow: var(--shadow-md);
}

/* Animations */
@keyframes pulseSlow {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.6; transform: scale(0.96); }
}

@keyframes floatGentle {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-6px); }
}

@keyframes shimmer {
  0% { background-position: -200% 0; }
  100% { background-position: 200% 0; }
}

/* Reveal on Scroll Helper */
.reveal {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 600ms cubic-bezier(0.16, 1, 0.3, 1), transform 600ms cubic-bezier(0.16, 1, 0.3, 1);
}

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

/* Accessibility */
@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;
  }
  .reveal {
    opacity: 1 !important;
    transform: none !important;
  }
}