<style>body {
    font-family: Arial, sans-serif;
    background: #f4f4f4;
    padding: 2rem;
}

.container {
    max-width: 900px;
    background: #fff;
    margin: 0 auto;
    padding: 2rem;
    border-radius: 8px;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

h1 {
    text-align: center;
    margin-bottom: 1rem;
}

.options {
    margin: 1rem 0;
    padding: 1rem;
    background: #eef;
    border-radius: 4px;
}

.options label {
    margin: 0 0.5rem 0.5rem 0;
    display: inline-block;
}

.options input[type="number"],
.options select {
    margin: 0 1rem 0.5rem 0;
    padding: 4px;
}

.buttons {
    text-align: center;
    margin: 1rem 0;
}

button {
    padding: 0.5rem 1rem;
    margin: 0.5rem;
    background-color: #007BFF;
    color: #fff;
    border: none;
    border-radius: 4px;
    cursor: pointer;
}

button:hover {
    background-color: #0056b3;
}

.back-btn {
    background-color: #6c757d;
}

.back-btn:hover {
    background-color: #5a6268;
}

#output {
    margin-top: 1.5rem;
    padding: 1rem;
    border: 1px solid #ddd;
    border-radius: 4px;
    background: #fff;
    min-height: 100px;
}