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

body {
    background: linear-gradient(135deg, #667eea, #764ba2);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}

.head {
    color: white;
    margin-bottom: 20px;
}

.container {
    background: #222;
    padding: 20px;
    border-radius: 12px;
    box-shadow: 0 15px 30px rgba(0,0,0,0.4);
}

.row {
    display: flex;
}

.input {
    width: 100%;
    height: 60px;
    font-size: 24px;
    margin-bottom: 10px;
    padding: 10px;
    text-align: right;
    border: none;
    outline: none;
    border-radius: 8px;
}

.btn {
    width: 70px;
    height: 70px;
    margin: 5px;
    font-size: 20px;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    background: #333;
    color: white;
    transition: 0.2s;
}

.btn:hover {
    background: #555;
}

.equal {
    background: #ff9500;
    color: white;
}

.equal:hover {
    background: #e08900;
}

.zero {
    width: 150px;
}