* {
    box-sizing: border-box;
}

body {
    margin: 0;
    background-color: #f3f5f7;
    color: #263238;
    font-family: Arial, sans-serif;
}

.navbar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
    padding: 1rem 2rem;
    background-color: #263238;
}

.navbar a {
    color: #ffffff;
    text-decoration: none;
}

.navbar-brand {
    font-size: 1.2rem;
    font-weight: bold;
}

.navbar-links {
    display: flex;
    flex-wrap: wrap;
    gap: 1.25rem;
}

.navbar a:hover {
    color: #80cbc4;
}

main {
    padding: 3rem 1rem;
}

.calculator {
    width: 100%;
    max-width: 420px;
    margin: 0 auto;
    padding: 2rem;
    border-radius: 8px;
    background-color: #ffffff;
    box-shadow: 0 4px 14px rgba(38, 50, 56, 0.12);
}

.calculator h1 {
    margin-top: 0;
    text-align: center;
}

.calculator h2 {
    padding: 0.75rem;
    border-radius: 4px;
    background-color: #e0f2f1;
    font-size: 1.1rem;
}

.calculator form {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.calculator input,
.calculator select,
.calculator button {
    width: 100%;
    min-height: 44px;
    padding: 0.7rem;
    border: 1px solid #cfd8dc;
    border-radius: 4px;
    font: inherit;
}

.calculator button {
    border: 0;
    background-color: #00897b;
    color: #ffffff;
    cursor: pointer;
    transition: background-color 150ms ease, transform 150ms ease;
}

.calculator button:hover {
    transform: translateY(-1px);
    background-color: #00695c;
}

.calculator button:focus-visible,
.navbar a:focus-visible {
    outline: 3px solid #80cbc4;
    outline-offset: 3px;
}

@media (max-width: 480px) {
    .navbar {
        align-items: flex-start;
        flex-direction: column;
        padding: 1rem;
    }

    main {
        padding: 1.5rem 1rem;
    }

    .calculator {
        padding: 1.5rem;
    }
}