body {
    font-family: Arial, sans-serif;
    line-height: 1.6;
    margin: 0;
    background-color: #f4f4f4;
    color: #333;
}

.container {
    display: flex;
}

.sidebar {
    width: 250px;
    background-color: #004c70;
    color: white;
    padding: 20px;
    height: 100vh;
    position: fixed;
    overflow-y: auto;
}

.sidebar h3 {
    color: #a7c0cd;
    margin-top: 20px;
    margin-bottom: 10px;
    font-size: 1.1em;
}

.sidebar ul {
    list-style: none;
    padding-left: 0;
}

.sidebar > nav > ul > li {
    margin-bottom: 10px;
}

.sidebar ul li a {
    color: white;
    text-decoration: none;
    display: block;
    padding: 8px 10px;
    border-radius: 4px;
    transition: background-color 0.3s;
    font-weight: bold;
}

.sidebar ul li a:hover {
    background-color: #005a87;
}

.sidebar .sub-topics {
    list-style: none;
    padding-left: 20px;
    margin-top: 5px;
}

.sidebar .sub-topics li a {
    font-weight: normal;
    font-size: 0.9em;
    padding: 6px 10px;
}


.main-content {
    margin-left: 270px; /* Sidebar width + some padding */
    flex-grow: 1;
}

.site-header {
    background-color: #005a87;
    color: white;
    padding: 20px 0;
    text-align: center;
}
.site-header nav ul {
    list-style: none;
    padding: 0;
}
.site-header nav ul li {
    display: inline;
    margin-right: 15px;
}
.site-header nav ul li a {
    color: white;
    text-decoration: none;
    font-weight: bold;
}
.site-header nav ul li a:hover {
    text-decoration: underline;
}
main {
    padding: 20px;
    max-width: 900px;
    margin: auto;
    background-color: white;
}
.intro {
    margin-bottom: 20px;
}
.featured-note {
    background-color: #e1f1ff;
    padding: 15px;
    border-left: 5px solid #005a87;
}
button, .button {
    background-color: #005a87;
    color: white;
    border: none;
    padding: 10px 15px;
    cursor: pointer;
    text-decoration: none;
    font-size: 16px;
    border-radius: 3px;
}
.content-image {
    max-width: 100%;
    height: auto;
    margin: 15px 0;
}
footer {
    text-align: center;
    margin-top: 30px;
    padding: 10px 0;
    background-color: #005a87;
    color: white;
}

/* New CSS for Dark Mode */
.dark-mode {
    background-color: #121212;
    color: #e0e0e0;
}

.dark-mode .sidebar {
    background-color: #002233;
}

.dark-mode .sidebar h3 {
    color: #88a1b0;
}

.dark-mode .sidebar ul li a:hover {
    background-color: #00334a;
}

.dark-mode .site-header {
    background-color: #00334a; /* Darker blue */
}
.dark-mode main {
    background-color: #1e1e1e;
}
.dark-mode .featured-note {
    background-color: #2c2c2c;
    border-left: 5px solid #4a90e2; /* Lighter accent */
}
.dark-mode button, .dark-mode .button {
    background-color: #4a90e2;
}
.dark-mode footer {
    background-color: #00334a;
}

/* Style for the Dark Mode Toggle button */
#dark-mode-toggle {
    position: absolute;
    top: 20px;
    right: 20px;
    padding: 8px 12px;
    font-size: 14px;
    background-color: #fff;
    color: #005a87;
    border: 1px solid #005a87;
    border-radius: 5px;
    cursor: pointer;
}
.dark-mode #dark-mode-toggle {
    background-color: #1e1e1e;
    color: #e0e0e0;
    border: 1px solid #e0e0e0;
}

/* New CSS for Formula Blocks */
.formula-block {
    background-color: #f0f8ff; /* Light blue background */
    border: 1px solid #cceeff;
    padding: 10px;
    font-family: 'Courier New', monospace; /* Monospace font for formulas */
    font-size: 1.1em;
    overflow-x: auto; /* for long formulas */
    border-radius: 5px;
    text-align: center;
    font-weight: bold;
}
.dark-mode .formula-block {
    background-color: #2b3a42; /* Darker background for dark mode */
    border: 1px solid #4a90e2;
    color: #f0f8ff;
}