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

body {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    background: linear-gradient(135deg, #74ebd5, #9face6);
}

.calculator {
    width: 340px;
    padding: 25px;
    background: rgba(255, 255, 255, 0.15);
    backdrop-filter: blur(15px);
    -webkit-backdrop-filter: blur(15px);
    border-radius: 20px;
    border: 1px solid rgba(255, 255, 255, 0.3);
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.2);
}

#display {
    width: 100%;
    height: 70px;
    background: rgba(255, 255, 255, 0.2);
    border: 1px solid rgba(255, 255, 255, 0.3);
    border-radius: 12px;
    color: #fff;
    font-size: 2em;
    text-align: right;
    padding: 0 15px;
    margin-bottom: 20px;
}

#display:focus {
    outline: none;
}

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

.btn {
    height: 60px;
    border: 1px solid rgba(255, 255, 255, 0.3);
    border-radius: 12px;
    background: rgba(255, 255, 255, 0.2);
    color: #fff;
    font-size: 1.3em;
    font-weight: 500;
    cursor: pointer;
    transition: background 0.2s, transform 0.1s;
}

.btn:hover {
    background: rgba(255, 255, 255, 0.35);
}

.btn:active {
    transform: scale(0.95);
}

.operator {
    background: rgba(255, 165, 0, 0.4);
}

.operator:hover {
    background: rgba(255, 165, 0, 0.6);
}

.clear {
    background: rgba(255, 70, 70, 0.4);
}

.clear:hover {
    background: rgba(255, 70, 70, 0.6);
}

.equals {
    background: rgba(70, 200, 120, 0.5);
    grid-row: span 2;
}

.equals:hover {
    background: rgba(70, 200, 120, 0.7);
}

.zero {
    grid-column: span 2;
}