:root {
    --bg-color: #f8f9fa;
    --text-color: #212529;
    --primary-color: #005a9c;
    --secondary-color: #e9ecef;
    --border-color: #dee2e6;
    --tag-behavior-bg: #fff0f3;
    --tag-behavior-text: #c92a2a;
    --tag-mechanics-bg: #e6f7ff;
    --tag-mechanics-text: #1864ab;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji";
    line-height: 1.7;
    background-color: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    padding: 20px;
}

.article-container {
    max-width: 800px;
    margin: 0 auto;
    background-color: #ffffff;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 2rem 3rem;
    box-shadow: 0 4px 12px rgba(0,0,0,0.05);
}

header {
    border-bottom: 2px solid var(--primary-color);
    padding-bottom: 1.5rem;
    margin-bottom: 2rem;
    text-align: center;
}

h1 {
    font-size: 2.5rem;
    color: var(--primary-color);
    margin: 0;
}

h2 {
    font-size: 1.8rem;
    color: var(--primary-color);
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 0.5rem;
    margin-top: 2.5rem;
    margin-bottom: 1.5rem;
}

h3 {
    font-size: 1.5rem;
    margin-top: 2rem;
    margin-bottom: 1rem;
}

h4 {
    font-size: 1.2rem;
    font-weight: 700;
    margin-top: 1.5rem;
    margin-bottom: 0.5rem;
}

p, ol, ul {
    font-size: 1.1rem;
    margin-bottom: 1.2rem;
}

ol, ul {
    padding-left: 1.5rem;
}

.subtitle {
    font-size: 1.2rem;
    color: #6c757d;
    margin-top: 0.5rem;
}

.series-nav {
    display: flex;
    justify-content: space-between;
    padding: 1rem;
    background-color: var(--secondary-color);
    border-radius: 6px;
    margin-bottom: 2rem;
}

.series-nav.bottom {
    margin-top: 3rem;
    margin-bottom: 0;
}

.nav-button {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
    padding: 0.5rem 1rem;
    border-radius: 4px;
    transition: background-color 0.2s ease-in-out;
}

.nav-button:hover {
    background-color: rgba(0, 90, 156, 0.1);
}

.nav-button.disabled {
    color: #6c757d;
    pointer-events: none;
    background-color: transparent;
}

.instructor-script {
    background-color: #fffbe6;
    border-left: 5px solid #fcc419;
    padding: 1rem 1.5rem;
    margin: 2rem 0;
    border-radius: 4px;
}

.instructor-script p {
    margin: 0;
    font-style: italic;
    color: #594b0a;
}

.protocol-block {
    background-color: #f1f3f5;
    padding: 2rem;
    border-radius: 8px;
    margin: 2.5rem 0;
}

.protocol-title {
    margin-top: 0;
    text-align: center;
}

.split-view {
    display: flex;
    gap: 2rem;
    margin-top: 1.5rem;
}

.split-half {
    flex: 1;
    min-width: 0;
}

.split-half ul {
    list-style-type: none;
    padding: 0;
}

.split-half li {
    background-color: #ffffff;
    padding: 0.8rem 1rem;
    border-radius: 4px;
    margin-bottom: 0.8rem;
    border: 1px solid var(--border-color);
}

.tag-behavior, .tag-mechanics {
    display: inline-block;
    font-weight: 700;
    font-size: 0.9rem;
    padding: 0.1rem 0.5rem;
    border-radius: 3px;
    margin-right: 0.5rem;
}

.tag-behavior {
    background-color: var(--tag-behavior-bg);
    color: var(--tag-behavior-text);
}

.tag-mechanics {
    background-color: var(--tag-mechanics-bg);
    color: var(--tag-mechanics-text);
}

@media (max-width: 768px) {
    .article-container {
        padding: 1.5rem;
    }
    h1 {
        font-size: 2rem;
    }
    .split-view {
        flex-direction: column;
        gap: 1rem;
    }
    .series-nav {
        flex-direction: column;
        align-items: center;
        gap: 0.5rem;
    }
}