* {
    box-sizing: border-box;
}

body {
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background: #000;
    font-family: Arial, sans-serif;
}

.calc {
    position: absolute;
    top: 10px;
    color: white;
}

.container {
    width: 90%;
    max-width: 350px;
    background: #ecf0f3;
    padding: 15px;
    border-radius: 12px;
}

#screen {
    width: 100%;
    height: 70px;
    font-size: 2rem;
    text-align: right;
    border: none;
    outline: none;
    padding: 10px;
    border-radius: 10px;
}

.btns {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    margin-top: 15px;
}

button {
    height: 55px;
    font-size: 1.1rem;
    border: none;
    border-radius: 8px;
    background: white;
    cursor: pointer;
}

button:hover {
    background: #ddd;
}

.equal {
    background: #33ccff;
    color: white;
}