* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: Arial, Helvetica, sans-serif;
}

body {
    background: #121212;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
}

.calculator {
    width: 460px;
    background: #1f1f1f;
    padding: 20px;
    border-radius: 20px;
    box-shadow: 0 15px 40px rgba(0, 0, 0, .4);
}

#display {
    width: 100%;
    height: 70px;
    border: none;
    outline: none;
    background: #2d2d2d;
    color: white;
    text-align: right;
    font-size: 2rem;
    padding: 15px;
    border-radius: 12px;
    margin-bottom: 20px;
}

.scientific-buttons {
    display: grid;
    grid-template-columns: repeat(6, 1fr);
    gap: 15px;
    margin-bottom: 20px;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 15px;
}

button {
    height: 65px;
    border: none;
    border-radius: 12px;
    font-size: 1.2rem;
    cursor: pointer;
    background: #333;
    color: white;
    transition: .2s;
}

button:hover {
    background: #444;
    transform: scale(.98);
}

.math {
    background: #6c5ce7;
}

.math:hover {
    background: #8477f5;
}

.operator {
    background: #ff9500;
}

.operator:hover {
    background: #ffac33;
}

.equal {
    background: #00b894;
}

.equal:hover {
    background: #00d9aa;
}

.clear {
    background: #e74c3c;
}

.clear:hover {
    background: #ff5f50;
}

.delete {
    background: #3498db;
}

.delete:hover {
    background: #4db8ff;
}

.ans {
    background: #00b894;
}

.ans:hover {
    background: #00d9aa;
}

.empty {
    visibility: hidden;
    pointer-events: none;
}