.simple-calc {
    width: 300px;
    background: #f8f9fa;
    border-radius: 10px;
    padding: 20px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    margin: 20px auto;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}

.calculator-display {
    margin-bottom: 20px;
}

.calculator-display input {
    width: 100%;
    height: 60px;
    border: none;
    background: #fff;
    font-size: 24px;
    text-align: right;
    padding: 0 15px;
    border-radius: 5px;
    box-shadow: inset 0 2px 5px rgba(0, 0, 0, 0.1);
}

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

.calc-btn {
    height: 50px;
    border: none;
    background: #fff;
    font-size: 18px;
    border-radius: 5px;
    cursor: pointer;
    transition: all 0.2s ease;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.calc-btn:hover {
    background: #f1f3f5;
    transform: translateY(-1px);
    box-shadow: 0 3px 6px rgba(0, 0, 0, 0.15);
}

.calc-btn:active {
    transform: translateY(1px);
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.1);
}

.calc-btn.operator {
    background: #e9ecef;
    color: #495057;
    font-weight: bold;
}

.calc-btn.equals {
    background: #228be6;
    color: white;
    grid-column: span 2;
}

.calc-btn.equals:hover {
    background: #1c7ed6;
}

.calc-btn.clear {
    background: #fa5252;
    color: white;
}

.calc-btn.clear:hover {
    background: #e03131;
}

/* Responsive Design */
@media (max-width: 400px) {
    .simple-calc {
        width: 100%;
        max-width: 300px;
        padding: 15px;
    }

    .calculator-display input {
        height: 50px;
        font-size: 20px;
    }

    .calc-btn {
        height: 45px;
        font-size: 16px;
    }
}