body {
    margin: 0;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

header {
    background-color: #333;
    color: white;
    padding: 15px 10px;
    text-align: center;
}

header h1 a {
    color: inherit;
    text-decoration: none;
}

main {
    flex: 1 0 auto;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 40px 20px;
}

.calculator-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    max-width: 400px;
    width: 100%;
    gap: 20px;
}

.calculator-container h2 {
    font-size: 2rem;
    margin: 0 0 20px 0;
    text-align: center;
}

.input-group {
    display: flex;
    flex-direction: column;
    width: 100%;
    text-align: center;
}

.input-group label {
    margin-bottom: 8px;
    font-weight: 500;
    font-size: 1rem;
}

.input-group input {
    padding: 12px;
    font-size: 1rem;
    border: 2px solid #ddd;
    border-radius: 4px;
    text-align: center;
    font-family: inherit;
}

.input-group input:focus {
    outline: none;
    border-color: #333;
}

button {
    padding: 12px 24px;
    font-size: 1rem;
    background-color: #333;
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-family: inherit;
    transition: background-color 0.2s;
}

button:hover {
    background-color: #555;
}

button:active {
    background-color: #222;
}

.result {
    margin-top: 20px;
    padding: 16px;
    font-weight: bold;
    font-size: 1.1rem;
    text-align: center;
    min-height: 24px;
    border-radius: 4px;
    background-color: #f5f5f5;
}

footer {
    background-color: #333;
    color: white;
    text-align: center;
    padding: 10px;
    width: 100%;
    flex-shrink: 0;
}

@media screen and (max-width: 600px) {
    header h1 {
        font-size: 1.5rem;
    }

    .calculator-container h2 {
        font-size: 1.5rem;
    }

    main {
        padding: 20px 10px;
    }

    .calculator-container {
        gap: 15px;
    }
}