/* Element name selector - applies to all body elements */
body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    margin: 0;
    padding: 0;
    background-color: #f4f4f4;
    color: #333;
}

/* Element name selector - applies to all header elements */
header {
    background-color: #2c3e50;
    color: white;
    text-align: center;
    padding: 2rem 1rem;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

/* Element name selector - applies to all h1 elements */
h1 {
    margin: 0;
    font-size: 2.5rem;
}

/* Element name selector - applies to all h2 elements */
h2 {
    color: #2c3e50;
    border-bottom: 3px solid #3498db;
    padding-bottom: 0.5rem;
    margin-top: 2rem;
}

/* Element name selector - applies to all h3 elements */
h3 {
    color: #34495e;
    margin-top: 1.5rem;
}

/* Element name selector - applies to all main elements */
main {
    max-width: 900px;
    margin: 2rem auto;
    padding: 2rem;
    background-color: white;
    box-shadow: 0 0 10px rgba(0,0,0,0.1);
    border-radius: 8px;
}

/* Element name selector - applies to all section elements */
section {
    margin-bottom: 2rem;
}

/* Element name selector - applies to all ul elements */
ul {
    background-color: #ecf0f1;
    padding: 1.5rem 2rem;
    border-radius: 5px;
    border-left: 4px solid #3498db;
}

/* Element name selector - applies to all ol elements */
ol {
    background-color: #e8f5e9;
    padding: 1.5rem 2rem;
    border-radius: 5px;
    border-left: 4px solid #27ae60;
}

/* Element name selector - applies to all li elements */
li {
    margin: 0.5rem 0;
}

/* Element name selector - applies to all img elements */
img {
    max-width: 100%;
    height: auto;
    display: block;
}

/* Element name selector - applies to all a elements */
a {
    color: #3498db;
    text-decoration: none;
    font-weight: bold;
}

a:hover {
    color: #2980b9;
    text-decoration: underline;
}

/* Element name selector - applies to all footer elements */
footer {
    background-color: #34495e;
    color: white;
    text-align: center;
    padding: 1rem;
    margin-top: 2rem;
}

/* ID selector - applies to element with id="main-title" */
#main-title {
    text-transform: uppercase;
    letter-spacing: 2px;
}

/* Class name selector - applies to elements with class="subtitle" */
.subtitle {
    font-size: 1.2rem;
    font-style: italic;
    margin-top: 0.5rem;
    color: #ecf0f1;
}

/* Class name selector - applies to elements with class="image-container" */
.image-container {
    text-align: center;
    margin: 2rem 0;
    padding: 1rem;
    background-color: #fafafa;
    border-radius: 8px;
}

/* Class name selector - applies to elements with class="bst-diagram" */
.bst-diagram {
    margin: 1rem auto;
    border: 2px solid #ddd;
    border-radius: 5px;
    padding: 1rem;
    background-color: white;
}

/* Class name selector - applies to elements with class="image-caption" */
.image-caption {
    font-size: 0.9rem;
    color: #666;
    font-style: italic;
    margin-top: 0.5rem;
}

/* Class name selector - applies to elements with class="highlight" */
.highlight {
    background-color: #fff3cd;
    padding: 1rem;
    border-left: 4px solid #ffc107;
    border-radius: 4px;
    font-weight: bold;
}

/* Class name selector - applies to elements with class="external-link" */
.external-link {
    display: inline-block;
    padding: 0.5rem 1rem;
    background-color: #3498db;
    color: white;
    border-radius: 5px;
    transition: background-color 0.3s ease;
}

.external-link:hover {
    background-color: #2980b9;
    text-decoration: none;
}

/* Additional styling for better appearance */
strong {
    color: #2c3e50;
}