/*!
 * Critical CSS for OBDWhiz - Above-the-fold styles only
 * Inlined in HTML head for immediate rendering
 * Total size: ~8KB optimized for LCP performance
 */

/* =================
   CSS VARIABLES & DESIGN SYSTEM (Essential)
   ================= */
:root {
  /* Brand Colors - Essential */
  --primary: #3b82f6;
  --primary-light: #60a5fa;
  --primary-dark: #2563eb;
  --primary-25: #f8faff;
  --primary-50: #eff6ff;
  --primary-100: #dbeafe;
  --primary-500: #3b82f6;
  --primary-600: #2563eb;
  --primary-700: #1d4ed8;

  /* Neutrals - Essential */
  --white: #ffffff;
  --gray-25: #fcfcfd;
  --gray-50: #f9fafb;
  --gray-100: #f3f4f6;
  --gray-200: #e5e7eb;
  --gray-300: #d1d5db;
  --gray-600: #4b5563;
  --gray-700: #374151;
  --gray-800: #1f2937;
  --gray-900: #111827;

  /* Typography */
  --font-primary: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-display: 'Plus Jakarta Sans', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'SF Mono', Monaco, 'Cascadia Code', 'Roboto Mono', Consolas, 'Courier New', monospace;

  /* Typography Scale - Essential */
  --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;

  /* Spacing Scale - Essential */
  --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-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --space-24: 6rem;

  /* Shadows - Essential */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);

  /* Border Radius - Essential */
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-2xl: 1.5rem;
  --radius-full: 9999px;

  /* Transitions - Essential */
  --transition-base: 200ms cubic-bezier(0.4, 0, 0.2, 1);
}

/* =================
   RESET & BASE STYLES (Critical)
   ================= */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

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

body {
  font-family: var(--font-primary);
  font-size: var(--text-base);
  line-height: 1.6;
  color: var(--gray-900);
  background-color: var(--white);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* =================
   LAYOUT SYSTEM (Critical)
   ================= */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--space-4);
}

@media (min-width: 640px) {
  .container {
    padding: 0 var(--space-6);
  }
}

@media (min-width: 1024px) {
  .container {
    padding: 0 var(--space-8);
  }
}

/* =================
   TYPOGRAPHY (Critical)
   ================= */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-display);
  font-weight: 700;
  line-height: 1.2;
  color: var(--gray-900);
  margin-bottom: var(--space-4);
}

h1 { font-size: var(--text-4xl); }
h2 { font-size: var(--text-3xl); }

@media (min-width: 768px) {
  h1 { font-size: var(--text-5xl); }
  h2 { font-size: var(--text-4xl); }
}

p {
  margin-bottom: var(--space-4);
  color: var(--gray-700);
}

/* =================
   HERO SECTION (Critical Above-the-fold)
   ================= */
.hero {
  position: relative;
  padding: var(--space-24) 0;
  background: linear-gradient(135deg, 
    var(--primary-25) 0%, 
    var(--white) 50%,
    var(--primary-50) 100%);
  overflow: hidden;
}

.hero-content {
  text-align: center;
  max-width: 800px;
  margin: 0 auto;
}

.hero-title {
  font-size: clamp(2.5rem, 5vw, 4rem);
  font-weight: 800;
  line-height: 1.1;
  margin-bottom: var(--space-6);
  background: linear-gradient(135deg, 
    var(--gray-900) 0%, 
    var(--primary-600) 50%, 
    var(--gray-800) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-subtitle {
  font-size: clamp(1.125rem, 2.5vw, 1.5rem);
  color: var(--gray-700);
  margin-bottom: var(--space-8);
  line-height: 1.6;
}

.hero-features {
  display: flex;
  justify-content: center;
  gap: var(--space-6);
  margin-bottom: var(--space-8);
  flex-wrap: wrap;
}

.feature-item {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  background: var(--white);
  padding: var(--space-3) var(--space-5);
  border-radius: var(--radius-full);
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--gray-200);
  font-weight: 600;
  color: var(--gray-700);
  transition: all var(--transition-base);
}

.feature-icon {
  font-size: 1.2em;
}

/* =================
   BUTTONS (Critical)
   ================= */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  font-family: var(--font-primary);
  font-weight: 600;
  text-decoration: none;
  border: none;
  border-radius: var(--radius-lg);
  cursor: pointer;
  transition: all var(--transition-base);
  outline: none;
  position: relative;
  overflow: hidden;
  white-space: nowrap;
}

.btn:focus-visible {
  outline: 2px solid var(--primary-500);
  outline-offset: 2px;
}

.btn-large {
  padding: var(--space-4) var(--space-8);
  font-size: var(--text-lg);
  min-height: 52px;
}

.btn-lookup {
  min-width: 140px;
  padding: var(--space-3) var(--space-8);
}

.btn-primary {
  background: linear-gradient(135deg, var(--primary-600) 0%, var(--primary-700) 100%);
  color: var(--white);
  box-shadow: var(--shadow-md);
}

.btn-secondary {
  background: var(--white);
  color: var(--gray-700);
  border: 1px solid var(--gray-300);
  box-shadow: var(--shadow-sm);
}

/* =================
   FORMS (Critical)
   ================= */
.form-group {
  margin-bottom: var(--space-6);
}

.form-label {
  display: block;
  margin-bottom: var(--space-2);
  font-weight: 600;
  color: var(--gray-900);
  font-size: var(--text-sm);
}

.form-input {
  width: 100%;
  padding: var(--space-3) var(--space-4);
  border: 1px solid var(--gray-300);
  border-radius: var(--radius-lg);
  font-size: var(--text-base);
  transition: all var(--transition-base);
  background: var(--white);
  font-family: var(--font-mono);
  text-transform: uppercase;
}

.form-input:focus {
  outline: none;
  border-color: var(--primary-500);
  box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.input-group {
  display: flex;
  gap: var(--space-3);
  align-items: flex-end;
}

.input-group .form-input {
  flex: 1;
}

/* =================
   HERO SPECIFIC STYLES (Critical)
   ================= */
.hero-lookup {
  max-width: 800px;
  margin: 0 auto;
}

.hero-lookup .form-group {
  margin: 0;
}

.hero-lookup .form-label {
  font-weight: 600;
  color: var(--gray-700);
  margin-bottom: var(--space-3);
  display: block;
  font-size: var(--text-lg);
}

.hero-lookup .input-group {
  display: flex;
  gap: var(--space-3);
  align-items: stretch;
}

.hero-lookup .form-input {
  flex: 1;
  padding: var(--space-4) var(--space-5);
  font-size: var(--text-lg);
  border: 2px solid var(--gray-300);
  border-radius: var(--radius-lg);
  background: var(--white);
  transition: all var(--transition-base);
}

.hero-lookup .btn-lookup {
  padding: var(--space-4) var(--space-6);
  font-size: var(--text-lg);
  white-space: nowrap;
}

.hero-hint {
  margin-top: var(--space-3);
  font-size: var(--text-sm);
  color: var(--gray-600);
  text-align: center;
}

/* =================
   SKIP NAVIGATION (Critical for Accessibility)
   ================= */
.skip-link {
  position: absolute;
  top: -40px;
  left: 6px;
  background: var(--primary-600);
  color: var(--white);
  padding: 8px 16px;
  text-decoration: none;
  border-radius: 4px;
  font-weight: 600;
  z-index: 2000;
  transition: top 0.3s;
}

.skip-link:focus {
  top: 6px;
}

/* =================
   UTILITY CLASSES (Critical)
   ================= */
.hidden {
  display: none !important;
}

/* Override for manual lookup panel - must be after .hidden */
.manual-lookup-panel.show {
  display: block !important;
}

.margin-left-3 {
  margin-left: var(--space-3) !important;
}

/* =================
   RESPONSIVE DESIGN (Critical Mobile-First)
   ================= */
@media (max-width: 640px) {
  .input-group {
    flex-direction: column;
    align-items: stretch;
  }

  .hero-lookup .input-group {
    flex-direction: column;
  }

  .hero-lookup .btn-lookup {
    width: 100%;
  }

  .hero-features {
    gap: var(--space-4);
  }
  
  .feature-item {
    padding: var(--space-2) var(--space-4);
    font-size: var(--text-sm);
  }
}

@media (max-width: 768px) {
  .form-input {
    font-size: 16px; /* Prevents zoom on iOS */
    padding: var(--space-4);
  }
  
  .hero-lookup .form-input {
    text-align: center;
    font-family: var(--font-mono);
    font-weight: 600;
    letter-spacing: 2px;
  }
}

/* =================
   ACCESSIBILITY (Critical)
   ================= */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

/* Focus indicators for better accessibility */
a:focus-visible {
  outline: 2px solid var(--primary-500);
  outline-offset: 2px;
  border-radius: 4px;
}