body {
    font-family: 'Segoe UI', sans-serif;
    background-color: #f0f2f5;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
}

.container {
    background: white;
    padding: 2.5rem;
    border-radius: 15px;
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
    text-align: center;
    width: 350px;
}

.input-group input {
    padding: 12px;
    margin: 10px 5px;
    border: 2px solid #eee;
    border-radius: 8px;
    width: 100px;
    transition: border-color 0.3s;
}

.input-group input:focus {
    border-color: #007bff;
    outline: none;
}

button {
    width: 100%;
    padding: 12px;
    background-color: #007bff;
    color: white;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 600;
}

.result-box {
    margin-top: 20px;
    padding: 15px;
    border-radius: 8px;
    min-height: 20px;
    font-weight: 500;
    color: #333;
    /* This keeps the box invisible until there is text */
    background-color: transparent; 
}

/* A little color if there's text inside */
.result-box:not(:empty) {
    background-color: #e9ecef;
}