body {
    background-color: #1a1a1a;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

.calculator {
    background-color: #1a1a1a;
    padding: 20px;
    border-radius: 30px;
    box-shadow: 10px 10px 30px #0d0d0d, -10px -10px 30px #272727;
    width: 320px;
}

.display {
    margin-bottom: 20px;
}

#result {
    width: 100%;
    height: 60px;
    background-color: #1a1a1a;
    border: none;
    border-radius: 10px;
    box-shadow: inset 4px 4px 8px #0d0d0d, inset -4px -4px 8px #272727;
    padding: 10px 15px;
    font-size: 24px;
    text-align: right;
    color: #e0e0e0;
    outline: none;
    box-sizing: border-box;
}

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

.btn {
    width: 60px;
    height: 60px;
    background-color: #1a1a1a;
    border: none;
    border-radius: 50%;
    box-shadow: 6px 6px 12px #0d0d0d, -6px -6px 12px #272727;
    font-size: 18px;
    font-weight: bold;
    color: #b0b0b0;
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    justify-content: center;
    align-items: center;
}

.btn:active {
    box-shadow: inset 4px 4px 8px #0d0d0d, inset -4px -4px 8px #272727;
    transform: scale(0.95);
}

.operator {
    color: #ff9f0a;
}

.scientific {
    color: #5e5ce6;
}

.clear {
    color: #ff453a;
}

.equal {
    background-color: #1a1a1a;
    color: #32d74b;
}

.backspace {
    grid-column: span 4;
    width: 100%;
    border-radius: 15px;
    margin-top: 10px;
}