.calculator {
    max-width: 500px;
    margin: 0 auto;
    text-align: center;
}

#relationText {
    width: 90%;
    padding: 1em;
    font-size: 1em;
    margin-bottom: 1em;
    border: 2px solid #4a90e2;
    border-radius: 8px;
    background: #f9f9f9;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    max-width: 400px;
    margin: 0 auto;
}


.buttons button {
    padding: 0.5em 1.2em;
    font-size: 1em;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    background: #4a90e2;
    color: white;
    transition: transform 0.2s;
}

.buttons button:hover {
    transform: scale(1.1);
    background: #357ab8;
}

.buttons .op {
    background: #aaa;
}

.buttons .calc {
    background: #e67e22;
}

.progress-container {
    width: 90%;
    background: #eee;
    border-radius: 8px;
    margin: 1em auto;
    height: 20px;
    display: none;
    overflow: hidden;
}

.progress-bar {
    height: 100%;
    background: #4caf50;
    width: 0%;
    transition: width 0.3s ease;
}

.result {
    margin-top: 1em;
    font-size: 1.1em;
    min-height: 2em;
}

.result .highlight {
    color: red;
    font-weight: bold;
}
.top-bar {
    text-align: center;
    margin-bottom: 1em;
}