/* General Reset and Body Styling - Element Name Selector */
body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    margin: 0;
    padding: 0;
    background-color: #f4f4f4;
    color: #333;
}

/* Header Styling - Element Name Selector */
header {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 2rem;
    text-align: center;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

/* Main Title - ID Selector */
#main-title {
    margin: 0;
    font-size: 2.5rem;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
}

/* Intro Text - Class Selector */
.intro-text {
    font-size: 1.2rem;
    margin-top: 0.5rem;
    font-style: italic;
}

/* Main Content Area - Element Name Selector */
main {
    max-width: 900px;
    margin: 2rem auto;
    padding: 0 1.5rem;
}

/* Content Sections - Class Selector */
.content-section {
    background: white;
    padding: 1.5rem;
    margin-bottom: 1.5rem;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

/* Heading Styling - Element Name Selectors */
h2 {
    color: #667eea;
    border-bottom: 2px solid #667eea;
    padding-bottom: 0.5rem;
    margin-top: 0;
}

h3 {
    color: #764ba2;
    margin-top: 1rem;
}

/* List Styling - Element Name Selectors */
ul, ol {
    padding-left: 2rem;
}

li {
    margin-bottom: 0.8rem;
}

/* Image Container - Class Selector */
.image-container {
    text-align: center;
    margin: 1.5rem 0;
}

/* BST Diagram - Class Selector */
.bst-diagram {
    max-width: 100%;
    height: auto;
    border: 2px solid #ddd;
    border-radius: 5px;
    padding: 1rem;
    background: white;
}

/* Image Caption - Class Selector */
.image-caption {
    font-style: italic;
    color: #666;
    margin-top: 0.5rem;
    font-size: 0.9rem;
}

/* Highlight Box - Class Selector */
.highlight-box {
    background-color: #fff3cd;
    border-left: 4px solid #ffc107;
    padding: 1rem;
    margin: 1rem 0;
    border-radius: 4px;
}

/* External Link - Class Selector */
.external-link {
    color: #667eea;
    text-decoration: none;
    font-weight: bold;
    transition: color 0.3s ease;
}

.external-link:hover {
    color: #764ba2;
    text-decoration: underline;
}

/* Footer - Element Name Selector */
footer {
    background-color: #333;
    color: white;
    text-align: center;
    padding: 1rem;
    margin-top: 2rem;
}

/* Paragraph Styling - Element Name Selector */
p {
    margin-bottom: 1rem;
}

/* Strong Text - Element Name Selector */
strong {
    color: #667eea;
}