:root {
    --button-bg: #2c2c2c;
    --button-active: #0066ff;
    --display-bg: #1a1a1a;
    --calculator-bg: #333333;
}

.calculator {
    background-color: var(--calculator-bg);
    padding: 20px;
    border-radius: 8px;
    width: 450px;
    margin: 0 auto;
    font-family: Arial, sans-serif;
}

.title-bar {
    display: flex;
    align-items: center;
    gap: 5px;
    padding: 5px;
    color: #ffffff;
    margin-bottom: 15px;
}

.dot {
    width: 12px;
    height: 12px;
    border-radius: 50%;
}

.red { background-color: #ff5f56; }
.yellow { background-color: #ffbd2e; }
.green { background-color: #27c93f; }

.display {
    background-color: var(--display-bg);
    border: 1px solid #444;
    border-radius: 4px;
    height: 60px;
    margin-bottom: 20px;
    padding: 10px;
    text-align: right;
    color: white;
    font-size: 24px;
    display: flex;
    align-items: center;
    justify-content: flex-end;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
}

.calculator button {
    background-color: var(--button-bg);
    border: 1px solid #444;
    border-radius: 4px;
    color: white;
    font-size: 20px;
    padding: 15px;
    cursor: pointer;
    transition: background-color 0.2s;
}

.calculator button:active, 
.calculator button.active {
    background-color: var(--button-active);
}

.zero {
    grid-column: span 2;
}

.equals {
    grid-row: span 2;
}

.footer {
    display: flex;
    justify-content: space-between;
    color: white;
    margin-top: 20px;
    font-size: 12px;
}