:root {
  /* Light theme */
  --bg-primary: #ffffff;
  --bg-secondary: #f8f9fa;
  --text-primary: #212529;
  --text-secondary: #6c757d;
  --border-color: #dee2e6;
  --accent-color: #ff4d4d;
  --accent-hover: #ff3333;
  --shadow: rgba(0, 0, 0, 0.1);
  --card-bg: #ffffff;
}

@media (prefers-color-scheme: dark) {
  :root {
    /* Dark theme */
    --bg-primary: #121212;
    --bg-secondary: #1e1e1e;
    --text-primary: #ffffff;
    --text-secondary: #b0b0b0;
    --border-color: #333333;
    --accent-color: #ff4d4d;
    --accent-hover: #ff3333;
    --shadow: rgba(0, 0, 0, 0.3);
    --card-bg: #1e1e1e;
  }
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  transition: background-color 0.3s, color 0.3s;
}

/* Header */
.site-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  max-width: 1200px;
  margin: 0 auto;
  padding: 1rem;
}

.brand {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--accent-color);
  text-decoration: none;
}

.theme-toggle {
  background: none;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  color: var(--text-primary);
  transition: transform 0.3s;
}

.theme-toggle:hover {
  transform: scale(1.1);
}

/* Main container */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 2rem 1rem;
}

/* Hero section */
.hero {
  text-align: center;
  margin-bottom: 3rem;
}

.eyebrow {
  color: var(--accent-color);
  font-weight: 600;
  letter-spacing: 1px;
  margin-bottom: 0.5rem;
  font-size: 0.875rem;
}

.animate-text {
  animation: fadeInUp 0.6s ease-out;
}

@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.animate-title {
  animation: fadeInUp 0.6s ease-out 0.2s forwards;
  opacity: 0;
}

.animate-subtitle {
  animation: fadeInUp 0.6s ease-out 0.4s forwards;
  opacity: 0;
}

.animate-hint {
  animation: fadeInUp 0.6s ease-out 0.6s forwards;
  opacity: 0;
}

.animate-footer {
  animation: fadeIn 0.6s ease-out 0.8s forwards;
  opacity: 0;
}

@keyframes fadeIn {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

h1 {
  font-size: 2.5rem;
  margin-bottom: 1rem;
  font-weight: 800;
}

.subtitle {
  font-size: 1.125rem;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto 2rem;
}

/* Download form */
.download-form {
  max-width: 600px;
  margin: 0 auto 1.5rem;
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
}

#videoUrl {
  flex: 1;
  min-width: 250px;
  padding: 0.75rem 1rem;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  background-color: var(--bg-secondary);
  color: var(--text-primary);
  font-size: 1rem;
  transition: border-color 0.3s, box-shadow 0.3s;
}

#videoUrl:focus {
  outline: none;
  border-color: var(--accent-color);
  box-shadow: 0 0 0 3px rgba(255, 77, 77, 0.2);
}

#downloadButton {
  background-color: var(--accent-color);
  color: white;
  border: none;
  border-radius: 8px;
  padding: 0.75rem 1.5rem;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  transition: background-color 0.3s, transform 0.2s;
  position: relative;
  overflow: hidden;
}

#downloadButton:hover {
  background-color: var(--accent-hover);
  transform: translateY(-2px);
}

#downloadButton:active {
  transform: translateY(0);
}

.spinner {
  width: 1rem;
  height: 1rem;
  border: 2px solid transparent;
  border-top-color: currentColor;
  border-radius: 50%;
  animation: spin 1s linear infinite;
  display: none;
}

#downloadButton.processing .spinner {
  display: inline-block;
}

#downloadButton.processing .button-label {
  opacity: 0.8;
}

@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}

.hint {
  color: var(--text-secondary);
  font-size: 0.875rem;
  max-width: 600px;
  margin: 0 auto;
}

/* Messages */
.message {
  margin-top: 1rem;
  padding: 0.75rem;
  border-radius: 8px;
  text-align: center;
  display: none;
}

.message.error {
  background-color: rgba(255, 77, 77, 0.1);
  color: #ff4d4d;
  border: 1px solid rgba(255, 77, 77, 0.3);
  display: block;
}

.message.success {
  background-color: rgba(40, 167, 69, 0.1);
  color: #28a745;
  border: 1px solid rgba(40, 167, 69, 0.3);
  display: block;
}

/* Result card */
.result-card {
  background-color: var(--card-bg);
  border-radius: 12px;
  box-shadow: 0 4px 12px var(--shadow);
  padding: 2rem;
  margin-top: 2rem;
  text-align: center;
  display: none;
}

.result-card.show {
  display: block;
  animation: slideIn 0.4s ease-out;
}

@keyframes slideIn {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.result-video {
  width: 100%;
  max-width: 400px;
  border-radius: 8px;
  margin: 0 auto 1.5rem;
  display: block;
}

.download-options {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  justify-content: center;
  margin-bottom: 1.5rem;
}

.btn-download {
  background-color: var(--accent-color);
  color: white;
  border: none;
  border-radius: 8px;
  padding: 0.5rem 1rem;
  font-size: 0.875rem;
  font-weight: 600;
  cursor: pointer;
  text-decoration: none;
  display: inline-block;
  transition: background-color 0.3s;
}

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

.video-info h3 {
  margin-bottom: 0.5rem;
  font-size: 1.25rem;
}

.video-info p {
  color: var(--text-secondary);
  margin-bottom: 1rem;
}

/* Footer */
.footer {
  text-align: center;
  padding: 2rem 1rem;
  color: var(--text-secondary);
  border-top: 1px solid var(--border-color);
  margin-top: 3rem;
}

.footer a {
  color: var(--accent-color);
  text-decoration: none;
}

.footer a:hover {
  text-decoration: underline;
}

.developer-credit {
  margin-top: 0.5rem;
  font-size: 0.875rem;
}

/* 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;
}

/* Responsive design */
@media (max-width: 768px) {
  .container {
    padding: 1rem;
  }
  
  h1 {
    font-size: 2rem;
  }
  
  .subtitle {
    font-size: 1rem;
  }
  
  .download-form {
    flex-direction: column;
  }
  
  #videoUrl,
  #downloadButton {
    width: 100%;
  }
  
  .result-card {
    padding: 1.5rem;
  }
  
  .download-options {
    flex-direction: column;
    align-items: center;
  }
  
  .btn-download {
    width: 100%;
    max-width: 300px;
  }
}