.calculator {
    max-width: 400px;
    margin: 70px auto;
    background: #fff;
    padding: 30px;
    border-radius: 10px;
    box-shadow: 0 2px 8px rgba(0, 82, 204, 0.2);
    box-sizing: border-box;
}

    .calculator h2 {
        text-align: center;
        margin-bottom: 20px;
        color: #2a5c91;
    }

.input-group {
    margin-bottom: 10px;
}

    .input-group label {
        display: block;
        margin: 10px auto 5px auto;
        width: 90%;
        color: #2a5c91;
    }

input[type="number"] {
    display: block;
    width: 90%;
    padding: 10px;
    margin: 0 auto;
    border: 1px solid #ccc;
    border-radius: 8px;
    box-sizing: border-box;
    background: #f8faff;
}

input.invalid {
    border-color: orange;
}

.input-hint {
    width: 90%;
    margin: 5px auto 0 auto;
    font-size: 13px;
    color: orange;
    display: none;
    text-align: left;
}

::selection {
    background: #007BFF; /* Selection background */
    color: white; /* Selection text color */
}

.calculate-btn {
    width: 90%;
    display: block;
    margin: 20px auto 0 auto;
    padding: 10px;
    margin-top: 20px;
    background: #2a5c91;
    color: white;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 16px;
}

    .calculate-btn:hover {
        opacity: 0.9;
        
    }

.result {
    margin-top: 20px;
    padding: 10px;
    border-radius: 8px;
    font-weight: bold;
    text-align: center;
}

.normal {
    background-color: #d4edda;
    color: #155724;
}

.warning {
    background-color: #fff3cd;
    color: #856404;
}

.danger {
    background-color: #f8d7da;
    color: #721c24;
}

@media (max-width: 600px) {
    .calculator {
        padding: 20px;
        width: 90%;
    }

    .calculate-btn {
        font-size: 15px;
        padding: 10px;
    }

    input, select {
        font-size: 15px;
    }
}