* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: Arial, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
}

.calculator {
    background: #333;
    border-radius: 15px;
    padding: 20px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
}

.display {
    margin-bottom: 15px;
}

#result {
    width: 100%;
    height: 60px;
    font-size: 24px;
    text-align: right;
    padding: 0 15px;
    border: none;
    border-radius: 8px;
    background: #222;
    color: white;
    outline: none;
}

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

button {
    height: 60px;
    font-size: 18px;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s;
    background: #666;
    color: white;
}

button:hover {
    background: #777;
    transform: translateY(-2px);
}

button:active {
    transform: translateY(0);
}

.equals {
    background: #ff6b35;
    grid-row: span 2;
}

.equals:hover {
    background: #ff7f50;
}

.zero {
    grid-column: span 2;
}