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

body {
    font-family: Arial, sans-serif;
    background-color: #2e2e2e;
    color: #ffffff;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
}

.container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    width: 80%;
    max-width: 1200px;
}

.manual {
    background-color: #333333;
    padding: 20px;
    border-radius: 10px;
    width: 30%;
    height: fit-content;
    margin-right: 30px;
}

.manual h2 {
    text-align: center;
    margin-bottom: 20px;
}

.manual ul {
    list-style-type: none;
}

.manual ul li {
    margin: 10px 0;
}

.calculator-box {
    background-color: #444444;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 0 15px rgba(0, 0, 0, 0.2);
    width: 60%;
}

.calculator {
    width: 100%;
}

.display {
    margin-bottom: 20px;
}

#output {
    width: 100%;
    height: 50px;
    font-size: 2rem;
    padding: 10px;
    text-align: right;
    background-color: #333333;
    color: #ffffff;
    border: none;
    border-radius: 5px;
}

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

button {
    background-color: #555555; /* All buttons black */
    border: none;
    color: white;
    font-size: 1.5rem;
    padding: 20px;
    border-radius: 5px;
    transition: background-color 0.3s ease;
}

button:hover {
    background-color: #888888;
}

button:active {
    background-color: #444444;
}

button:focus {
    outline: none;
}

button:nth-child(4n), button:nth-child(5), button:nth-child(6), button:nth-child(7), button:nth-child(8), button:nth-child(9) {
    background-color: #555555; /* All numbers and operators are black */
}

/* Only the DEL, C, and = buttons in orange */
button:nth-last-child(2), button:nth-child(12), button:nth-child(16) {
    background-color: #ff8c00; /* Orange color */
}

button:last-child {
    background-color: #ff8c00; /* Orange equal button */
}

button:nth-last-child(2) {
    background-color: #ff8c00; /* Orange DEL button */
}

.calculator-box {
    width: 100%;
}