/* Mobile-First CSS for AI Sheet Filler */

:root {
  --color-primary: #2563eb;
  --color-primary-dark: #1e40af;
  --color-text: #1f2937;
  --color-text-light: #6b7280;
  --color-bg: #ffffff;
  --color-bg-alt: #f9fafb;
  --color-border: #e5e7eb;
  --color-accent: #22c55e;
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2rem;
  --spacing-xl: 3rem;
  --spacing-2xl: 4rem;
  --max-width: 1200px;
  --border-radius: 0.5rem;
  --transition: 0.2s ease;
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  line-height: 1.6;
  color: var(--color-text);
  background-color: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  line-height: 1.2;
  margin-bottom: var(--spacing-sm);
  color: var(--color-text);
}

h1 {
  font-size: 2rem;
  margin-bottom: var(--spacing-md);
}

h2 {
  font-size: 1.75rem;
  margin-top: var(--spacing-xl);
  margin-bottom: var(--spacing-md);
}

h3 {
  font-size: 1.5rem;
  margin-top: var(--spacing-lg);
  margin-bottom: var(--spacing-sm);
}

h4 {
  font-size: 1.25rem;
  margin-top: var(--spacing-md);
  margin-bottom: var(--spacing-xs);
}

p {
  margin-bottom: var(--spacing-sm);
}

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

a:hover {
  color: var(--color-primary-dark);
}

ul, ol {
  margin-left: var(--spacing-md);
  margin-bottom: var(--spacing-sm);
}

li {
  margin-bottom: var(--spacing-xs);
}

/* Layout */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--spacing-md);
}

/* Header */
header {
  background-color: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  padding: var(--spacing-md) 0;
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(10px);
  background-color: rgba(255, 255, 255, 0.95);
}

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

.logo {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--color-text);
}

.logo img {
  width: 32px;
  height: 32px;
}

.github-link {
  display: flex;
  align-items: center;
  padding: var(--spacing-xs);
  color: var(--color-text);
  transition: opacity var(--transition);
}

.github-link:hover {
  opacity: 0.7;
}

.github-link svg {
  width: 24px;
  height: 24px;
}

/* Main Content */
main {
  min-height: calc(100vh - 200px);
  padding: var(--spacing-xl) 0;
}

section {
  margin-bottom: var(--spacing-2xl);
}

/* Hero Section */
.hero {
  text-align: center;
  padding: var(--spacing-2xl) 0;
}

.hero h1 {
  font-size: 2.5rem;
  margin-bottom: var(--spacing-md);
}

.hero p {
  font-size: 1.125rem;
  color: var(--color-text-light);
  max-width: 600px;
  margin: 0 auto var(--spacing-lg);
}

/* Features */
.features {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-md);
  margin-top: var(--spacing-lg);
}

.feature-item {
  padding: var(--spacing-md);
  background-color: var(--color-bg-alt);
  border-radius: var(--border-radius);
  border: 1px solid var(--color-border);
}

.feature-item h3 {
  margin-top: 0;
  color: var(--color-primary);
}

/* Videos */
.videos {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-lg);
  margin-top: var(--spacing-lg);
}

.video-item {
  position: relative;
  padding-bottom: 56.25%; /* 16:9 aspect ratio */
  height: 0;
  overflow: hidden;
  border-radius: var(--border-radius);
  background-color: var(--color-bg-alt);
  border: 1px solid var(--color-border);
}

.video-item iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}

.video-placeholder {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  text-align: center;
  padding: var(--spacing-md);
}

.video-placeholder h4 {
  color: white;
  margin-bottom: var(--spacing-xs);
}

/* Examples */
.examples {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-lg);
  margin-top: var(--spacing-lg);
}

.example-item {
  padding: var(--spacing-lg);
  background-color: var(--color-bg-alt);
  border-radius: var(--border-radius);
  border-left: 4px solid var(--color-accent);
}

.example-item h3 {
  margin-top: 0;
  color: var(--color-text);
}

.example-prompt {
  font-weight: 600;
  color: var(--color-primary);
  margin-top: var(--spacing-sm);
}

.example-description {
  margin-top: var(--spacing-sm);
  color: var(--color-text-light);
}

/* Footer */
footer {
  background-color: var(--color-bg-alt);
  border-top: 1px solid var(--color-border);
  padding: var(--spacing-xl) 0;
  margin-top: var(--spacing-2xl);
}

.footer-content {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
  text-align: center;
}

.footer-links {
  display: flex;
  justify-content: center;
  gap: var(--spacing-lg);
  flex-wrap: wrap;
}

.footer-links a {
  color: var(--color-text-light);
}

.footer-links a:hover {
  color: var(--color-primary);
}

/* Legal Pages */
.legal-content {
  max-width: 800px;
  margin: 0 auto;
}

.legal-content h1 {
  margin-bottom: var(--spacing-lg);
}

.legal-content h2 {
  margin-top: var(--spacing-xl);
  padding-top: var(--spacing-lg);
  border-top: 1px solid var(--color-border);
}

.legal-content h2:first-of-type {
  border-top: none;
  padding-top: 0;
}

.legal-content h3 {
  margin-top: var(--spacing-lg);
}

.legal-content ul {
  margin-left: var(--spacing-lg);
}

.legal-content code {
  background-color: var(--color-bg-alt);
  padding: 0.125rem 0.25rem;
  border-radius: 0.25rem;
  font-size: 0.9em;
}

/* Responsive Design - Tablet */
@media (min-width: 768px) {
  html {
    font-size: 17px;
  }

  h1 {
    font-size: 2.5rem;
  }

  h2 {
    font-size: 2rem;
  }

  .hero h1 {
    font-size: 3rem;
  }

  .features {
    grid-template-columns: repeat(2, 1fr);
  }

  .videos {
    grid-template-columns: repeat(2, 1fr);
  }

  .examples {
    grid-template-columns: repeat(2, 1fr);
  }

  .footer-content {
    flex-direction: row;
    justify-content: space-between;
    align-items: center;
    text-align: left;
  }
}

/* Responsive Design - Desktop */
@media (min-width: 1024px) {
  .container {
    padding: 0 var(--spacing-xl);
  }

  .features {
    grid-template-columns: repeat(3, 1fr);
  }

  .videos {
    grid-template-columns: repeat(3, 1fr);
  }

  .examples {
    grid-template-columns: repeat(3, 1fr);
  }

  header {
    padding: var(--spacing-lg) 0;
  }

  .logo img {
    width: 40px;
    height: 40px;
  }
}

/* Accessibility */
@media (prefers-reduced-motion: reduce) {
  * {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

/* Focus styles */
a:focus,
button:focus {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}