body {
    font-family: Arial, sans-serif;
    background-color: #f9fafb;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
}

.calculator {
    background-color: #ffffff;
    border-radius: 20px;
    padding: 20px;
    width: 320px;
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.1);
}

.display-wrapper {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 20px;
}

.history-icon {
    font-size: 1.5rem;
    color: #7d7d7d;
    margin-right: 10px;
}

.display {
    width: 100%;
    height: 50px;
    border: none;
    border-radius: 10px;
    font-size: 1.5rem;
    text-align: right;
    padding: 10px;
    box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.1);
    background-color: #f4f4f4;
    color: #333;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    gap: 10px;
}

.btn {
    height: 50px;
    border: none;
    border-radius: 25px;
    font-size: 1rem;
    cursor: pointer;
    background-color: #f0f4fa;
    color: #333;
    transition: all 0.3s ease;
}

.btn.mode {
    color: #007aff;
    background-color: #eaf2ff;
}

.btn.operator {
    background-color: #fbe4e4;
    color: #e53935;
}

.btn.equal {
    grid-column: span 2;
    background-color: #4caf50;
    color: white;
}

.btn:hover {
    filter: brightness(0.9);
}