:root {
  --primary-color: #3498db;
  --secondary-color: #2c3e50;
  --accent-color: #1abc9c;
  --light-gray: #f5f5f5;
  --dark-gray: #333;
  --text-color: #222;
  --card-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
  --transition-speed: 0.3s;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  line-height: 1.6;
  color: var(--text-color);
  background-color: var(--light-gray);
  padding: 20px;
  max-width: 1200px;
  margin: 0 auto;
}

header {
  text-align: center;
  margin-bottom: 30px;
  padding: 20px;
}

header h1 {
  color: var(--secondary-color);
  margin-bottom: 10px;
  font-size: 2.2rem;
}

header p {
  color: var(--dark-gray);
  font-size: 1.1rem;
}

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

a:hover {
  color: var(--accent-color);
  text-decoration: underline;
}

.card {
  background-color: white;
  border-radius: 8px;
  box-shadow: var(--card-shadow);
  padding: 20px;
  margin-bottom: 20px;
}

.card h3 {
  color: var(--secondary-color);
  margin-bottom: 15px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--light-gray);
}

.collapsible-trigger {
  cursor: pointer;
  position: relative;
}

.collapsible-trigger::after {
  content: '▼';
  position: absolute;
  right: 0;
  transform: rotate(0deg);
  transition: transform var(--transition-speed) ease;
}

.collapsible-trigger.active::after {
  transform: rotate(180deg);
}

.collapsible-content {
  max-height: 0;
  overflow: hidden;
  transition: max-height var(--transition-speed) ease;
}

.collapsible-content.active {
  max-height: 1000px;
}

.cta-button {
  display: inline-block;
  background-color: var(--primary-color);
  color: white;
  padding: 12px 24px;
  border-radius: 4px;
  font-weight: bold;
  text-align: center;
  margin: 15px 0;
}

.cta-button:hover {
  background-color: var(--accent-color);
  text-decoration: none;
}

pre {
  background-color: var(--light-gray);
  padding: 15px;
  border-radius: 4px;
  overflow-x: auto;
  margin: 15px 0;
}

code {
  font-family: 'Courier New', Courier, monospace;
}

.copy-btn {
  position: absolute;
  top: 5px;
  right: 5px;
  background-color: var(--secondary-color);
  color: white;
  border: none;
  border-radius: 4px;
  padding: 5px 10px;
  cursor: pointer;
  font-size: 0.8rem;
}

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

ul, ol {
  margin-left: 20px;
  margin-bottom: 15px;
}

li {
  margin-bottom: 8px;
}

.note {
  font-size: 0.9rem;
  color: #666;
  font-style: italic;
}

.video-container {
  position: relative;
  width: 100%;
  max-width: 800px;
  height: 450px;
  margin: 0 auto;
  background: #fff;
}

#youtube-player {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}

.video-info {
  margin-top: 20px;
  padding-top: 15px;
  border-top: 1px solid var(--light-gray);
}

.footer {
  text-align: center;
  margin-top: 40px;
  padding: 20px;
  color: #888;
  font-size: 0.9rem;
}