```css
body {
    font-family: Arial, sans-serif;
    background: #f5f5f5;
    margin: 0;
    padding: 0;
}

.container {
    max-width: 850px;
    margin: 40px auto;
    padding: 20px;
}

h1 {
    text-align: center;
    margin-bottom: 10px;
}

.subtitle {
    text-align: center;
    font-size: 18px;
    margin-bottom: 30px;
}

.card {
    background: white;
    padding: 25px;
    margin-bottom: 20px;
    border-radius: 10px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.08);
}

.info-box {
    background: #e8f0fe;
    padding: 18px;
    border-radius: 10px;
    margin-bottom: 20px;
}

select,
input {
    padding: 10px;
    font-size: 16px;
    margin-top: 8px;
    margin-bottom: 20px;
}

select {
    width: 100%;
}

.bid-area {
    display: flex;
    gap: 10px;
    align-items: center;
}

input {
    width: 120px;
}

button {
    padding: 11px 20px;
    font-size: 16px;
    cursor: pointer;
    border: none;
    border-radius: 6px;
    background: #333;
    color: white;
}

button:hover {
    opacity: 0.85;
}

#result {
    padding: 15px;
    background: #f1f1f1;
    border-radius: 8px;
    line-height: 1.7;
}

.explanation {
    line-height: 1.6;
}

strong {
    font-weight: bold;
}

@media (max-width: 600px) {

    .container {
        margin: 15px auto;
        padding: 10px;
    }

    .bid-area {
        flex-direction: column;
        align-items: flex-start;
    }

}
```