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

/* Body */
body {
    height: 100vh;
    background: linear-gradient(to right, #2196f3, #21cbf3);

    display: flex;
    justify-content: center;
    align-items: center;
}

/* Calculator Box */
.calculator {
    background: white;
    width: 300px;
    padding: 20px;

    border-radius: 15px;
    box-shadow: 0 10px 25px rgba(0,0,0,0.2);
}

/* Display */
#display {
    width: 100%;
    height: 60px;

    font-size: 26px;
    text-align: right;

    padding: 10px;

    border: none;
    outline: none;

    background: #f5f5f5;
    border-radius: 8px;

    margin-bottom: 15px;
}

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

/* Button Style */
button {
    height: 55px;

    font-size: 18px;
    font-weight: bold;

    border: none;
    border-radius: 8px;

    background: #e0e0e0;
    cursor: pointer;

    transition: 0.2s;
}

button:hover {
    background: #d5d5d5;
}

/* Special Buttons */
.clear {
    background: #f44336;
    color: white;
}

.clear:hover {
    background: #e53935;
}

.equal {
    background: #4caf50;
    color: white;

    grid-row: span 2;
}

.equal:hover {
    background: #43a047;
}

.zero {
    grid-column: span 2;
}