body {
    font-family: 'Arial', sans-serif;
    background-color: #f4f4f9;
    margin: 0;

    padding: 0;
    display: flex;
    flex-direction: column;
    align-items: center;
}

header {
    background-color: #3f51b5;
    color: white;
    width: 100%;
    padding: 1rem 0 1rem 0;
    text-align: center;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

h1 {
    margin: 0;
}

main {
    line-height: 1.6;
    padding: 2rem;
    max-width: 800px;
    width: 100%;
}

.introduction,
.additional-content,
.conclusion {
    background-color: white;
    padding: 2rem;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    margin-bottom: 2rem;
}

.calculator,
.theory>div {
    background-color: white;
    padding: 2rem;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    margin-bottom: 2rem;
}

h2,
h3 {
    margin-top: 0;
}

label {
    display: block;
    margin: 1rem 0 0.5rem;
}

input[type="number"] {
    width: calc(100% - 20px);
    padding: 0.5rem;
    margin-bottom: 1rem;
    border: 1px solid #ccc;
    border-radius: 4px;
}

button {
    background-color: #3f51b5;
    color: white;
    border: none;
    padding: 0.5rem 1rem;
    border-radius: 4px;
    cursor: pointer;
}

button:hover {
    background-color: #303f9f;
}

p {
    margin: 1rem 0 0;
}

.formula {
    font-family: 'Courier New', Courier, monospace;
    font-size: 1.2em;
    color: #333;
    margin: 1rem 0;
}

ul {
    list-style-type: disc;
    padding-left: 1.5rem;
}

ul li {
    margin-bottom: 0.5rem;
}

.theory div {
    margin-bottom: 20px;
}

.theory div>h2 {
    text-decoration: underline;
}