* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-color: #080808;
}

.calculator {
    width: 320px;
    background-color: #17181a;
    padding: 20px;
    border-radius: 20px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
}

#display {
    width: 100%;
    height: 70px;
    background-color: transparent;

    overflow-x: auto;
    white-space: nowrap;

    border: none;
    outline: none;
    text-align: right;
    color: #ffffff;
    font-size: 2.5rem;
    padding: 10px;
    margin-bottom: 20px;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 12px;
}

.btn {
    height: 60px;
    border-radius: 50px;
    border: none;
    outline: none;
    font-size: 1.5rem;
    font-weight: 600;
    background-color: #2d2f31;
    color: #ffffff;
    cursor: pointer;
    transition: background-color 0.2s ease;
}

.btn:hover {
    background-color: #3e4144;
}

.btn.operator {
    color: #ff9f0a;
    background-color: #2d2f31;
}

.btn.operator:hover {
    background-color: #3e4144;
}

.btn.clear, .btn.delete {
    color: #ff453a;
}

.btn.equal {
    background-color: #ff9f0a;
    color: #ffffff;
    grid-row: span 2;
    height: 132px;
}

.btn.equal:hover {
    background-color: #e08b07;
}

.btn.zero {
    grid-column: span 2;
    border-radius: 50px;
    text-align: left;
    padding-left: 22px;
}