/* ===== CSS Variables ===== */
:root {
  /* Colors - Dark Tech Theme */
  --color-bg-primary: #0a0b0e;
  --color-bg-secondary: #15171c;
  --color-bg-tertiary: #1f2128;
  --color-bg-elevated: #252a33;
  
  --color-text-primary: #f8fafc;
  --color-text-secondary: #94a3b8;
  --color-text-muted: #64748b;
  
  --color-primary: #00d4ff;
  --color-primary-hover: #33ddff;
  --color-primary-subtle: rgba(0, 212, 255, 0.1);
  
  --color-success: #00ff9d;
  --color-success-subtle: rgba(0, 255, 157, 0.1);
  
  --color-warning: #ffaa00;
  --color-warning-subtle: rgba(255, 170, 0, 0.1);
  
  --color-danger: #ff3366;
  --color-danger-subtle: rgba(255, 51, 102, 0.1);
  
  --color-border: #2d3748;
  --color-border-subtle: rgba(45, 55, 72, 0.5);
  
  /* Typography */
  --font-sans: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', Consolas, monospace;
  
  --text-xs: 0.75rem;
  --text-sm: 0.875rem;
  --text-base: 1rem;
  --text-lg: 1.125rem;
  --text-xl: 1.25rem;
  --text-2xl: 1.5rem;
  --text-3xl: 1.875rem;
  --text-4xl: 2.25rem;
  --text-5xl: 3rem;
  
  --leading-tight: 1.25;
  --leading-normal: 1.5;
  --leading-relaxed: 1.75;
  
  /* Spacing Scale (0–96px) */
  --space-0: 0;
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --space-24: 6rem;
  
  /* Radius */
  --radius-sm: 0.25rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-2xl: 1.5rem;
  --radius-full: 9999px;
  
  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4), 0 2px 4px -1px rgba(0, 0, 0, 0.2);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.5), 0 4px 6px -2px rgba(0, 0, 0, 0.3);
  --shadow-neon: 0 0 20px rgba(0, 212, 255, 0.15);
  --shadow-neon-strong: 0 0 30px rgba(0, 212, 255, 0.3);
  
  /* Transitions */
  --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-base: 200ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 300ms cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  line-height: var(--leading-normal);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  font-feature-settings: "liga" 1, "calt" 1;
}

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

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

p, h1, h2, h3, h4, h5, h6 {
  overflow-wrap: break-word;
}

ul, ol {
  list-style: none;
}

/* ===== Base Styles ===== */
body {
  font-family: var(--font-sans);
  background-color: var(--color-bg-primary);
  color: var(--color-text-secondary);
  min-height: 100vh;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  color: var(--color-text-primary);
  font-weight: 700;
  line-height: var(--leading-tight);
  letter-spacing: -0.02em;
}

h1 { font-size: var(--text-4xl); }
h2 { font-size: var(--text-3xl); }
h3 { font-size: var(--text-2xl); }
h4 { font-size: var(--text-xl); }
h5 { font-size: var(--text-lg); }
h6 { font-size: var(--text-base); }

@media (min-width: 768px) {
  h1 { font-size: var(--text-5xl); }
}

p {
  margin-bottom: var(--space-4);
}

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

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

a:hover {
  color: var(--color-primary-hover);
  text-shadow: 0 0 10px rgba(0, 212, 255, 0.5);
}

/* ===== Utilities ===== */
.container {
  width: 100%;
  max-width: 1280px;
  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);
  }
}

/* Flexbox utilities */
.flex { display: flex; }
.flex-col { flex-direction: column; }
.items-center { align-items: center; }
.justify-center { justify-content: center; }
.justify-between { justify-content: space-between; }
.gap-1 { gap: var(--space-1); }
.gap-2 { gap: var(--space-2); }
.gap-4 { gap: var(--space-4); }
.gap-6 { gap: var(--space-6); }
.gap-8 { gap: var(--space-8); }

/* Grid utilities */
.grid { display: grid; }
.grid-cols-1 { grid-template-columns: repeat(1, minmax(0, 1fr)); }
.grid-cols-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid-cols-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.grid-cols-4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }

@media (min-width: 768px) {
  .md\:grid-cols-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .md\:grid-cols-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .md\:grid-cols-4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
}

/* Screen reader only */
.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;
}

/* ===== Components ===== */
/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-6);
  font-size: var(--text-sm);
  font-weight: 600;
  line-height: 1;
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
  background-color: transparent;
  color: var(--color-text-primary);
  cursor: pointer;
  transition: all var(--transition-fast);
  position: relative;
  overflow: hidden;
}

.btn::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(45deg, transparent, rgba(255, 255, 255, 0.05), transparent);
  transform: translateX(-100%);
  transition: transform var(--transition-slow);
}

.btn:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
  box-shadow: var(--shadow-neon);
}

.btn:hover::before {
  transform: translateX(100%);
}

.btn:active {
  transform: translateY(1px);
}

.btn:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  border-color: var(--color-border);
  color: var(--color-text-muted);
  box-shadow: none;
}

.btn--primary {
  background-color: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-bg-primary);
}

.btn--primary:hover {
  background-color: var(--color-primary-hover);
  border-color: var(--color-primary-hover);
  color: var(--color-bg-primary);
  box-shadow: var(--shadow-neon-strong);
}

/* Form Inputs */
.input {
  width: 100%;
  padding: var(--space-3) var(--space-4);
  font-size: var(--text-base);
  line-height: var(--leading-normal);
  background-color: var(--color-bg-secondary);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  color: var(--color-text-primary);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.input:hover {
  border-color: var(--color-text-muted);
}

.input:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px var(--color-primary-subtle);
}

.input::placeholder {
  color: var(--color-text-muted);
}

.input:disabled {
  opacity: 0.6;
  cursor: not-allowed;
  background-color: var(--color-bg-tertiary);
}

/* Cards */
.card {
  background-color: var(--color-bg-secondary);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  transition: transform var(--transition-base), box-shadow var(--transition-base), border-color var(--transition-base);
}

.card:hover {
  transform: translateY(-2px);
  border-color: rgba(0, 212, 255, 0.3);
  box-shadow: var(--shadow-lg), var(--shadow-neon);
}

.card--elevated {
  background-color: var(--color-bg-tertiary);
  border-color: var(--color-border-subtle);
}

/* ===== Accessibility ===== */
:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

@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;
  }
  
  .btn::before {
    display: none;
  }
}

@media (prefers-contrast: high) {
  :root {
    --color-border: #ffffff;
    --color-text-secondary: #ffffff;
  }
}