body,
html {
    margin: 0;
    padding: 0;
    height: 100%;
    background-color: #1a1a1a;
    font-family: Arial, sans-serif;
    overflow: hidden;
}

.background {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: #3498db;
    z-index: -1;
}

.calculator {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 320px;
    padding: 20px;
    border: 2px solid #3498db;
    border-radius: 10px;
    background-color: #ecf0f1;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
    text-align: center;
}

#result {
    width: calc(100% - 10px);
    margin-bottom: 10px;
    padding: 10px;
    border: 2px solid #3498db;
    border-radius: 5px;
    font-size: 24px;
}

.button-row {
    display: flex;
    justify-content: center;
    margin-bottom: 10px;
}

.button {
    width: 60px;
    height: 60px;
    margin: 5px;
    border: none;
    border-radius: 10px;
    cursor: pointer;
    outline: none;
    font-size: 24px;
    background-color: #d1d8e0;
    color: #333;
    transition: background-color 0.3s, color 0.3s, transform 0.2s;
}

.button:hover {
    background-color: #3498db;
    color: white;
    transform: scale(1.1);
}

.button:active {
    transform: scale(0.9);
}

.button.primary {
    background-color: #3498db;
    color: white;
}

.button.warning {
    background-color: #e67e22;
    color: white;
}

.button.danger {
    background-color: #d24229;
    color: white;
}

.button.equal {
    background-color: #333;
    color: white;
}