* {
    box-sizing: border-box;
}

body {
    margin: 0;
    min-height: 100vh;

    display: flex;
    justify-content: center;
    align-items: center;

    font-family: Arial, sans-serif;
    background-color: #f4f4f4;
}

.calculator {
    width: 90%;
    max-width: 420px;

    padding: 32px;

    background-color: white;
    border-radius: 16px;

    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.1);
}

h1 {
    margin-top: 0;
    margin-bottom: 8px;
}

.calculator > p:first-of-type {
    margin-top: 0;
    margin-bottom: 24px;
    color: #666666;
}

label {
    display: block;
    margin-bottom: 8px;
}

input[type="number"] {
    width: 100%;
    padding: 12px 14px;
    margin-bottom: 20px;

    font-size: 16px;

    border: 1px solid #cccccc;
    border-radius: 8px;
}

input[type="number"]:focus {
    outline: none;
    border-color: #333333;
}

button {
    width: 100%;
    padding: 14px;
    margin-top: 24px;

    font-size: 16px;
    font-weight: bold;

    border: none;
    border-radius: 8px;

    background-color: #222222;
    color: white;

    cursor: pointer;
}

button:hover {
    background-color: #444444;
}

.result {
    margin-top: 24px;
    margin-bottom: 0;

    padding: 16px;

    font-size: 18px;
    font-weight: bold;

    background-color: #f2f2f2;
    border-radius: 8px;
}

.gender-title {
    margin-top: 4px;
    margin-bottom: 8px;
}

.gender-options {
    display: flex;
    gap: 12px;
}

.gender-option {
    flex: 1;
    margin-bottom: 0;
    cursor: pointer;
}

.gender-option input {
    position: absolute;
    opacity: 0;
    pointer-events: none;
}

.gender-option span {
    display: flex;
    justify-content: center;
    align-items: center;

    min-height: 58px;
    padding: 14px;

    font-size: 18px;
    font-weight: bold;

    border: 2px solid #cccccc;
    border-radius: 10px;

    background-color: white;
}

.gender-option input:checked + span {
    border-color: #222222;
    background-color: #222222;
    color: white;
}