body {
    margin: 0;
    padding: 0;
    font-family: Arial, sans-serif;
}

.calc {
    margin: 50px auto;
    padding: 18px;
    width: 300px;
    height: 530px;
    border-radius: 20px;
    background: var(--bg);
    color: #fff;
    box-shadow: 4px 4px 4px #4f4f4f;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: space-between;
}

.title{
    margin: 0;

    font-size: 28px;
    font-weight: 300;
    text-align: center;
    color: var(--color-accent);
}

.calc-screen {
    height: 125px;
    padding: 10px;
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
    align-items: flex-end;
    margin-bottom: 20px;
}

.expression {
    color: rgba(255, 255, 255, 0.7);
    font-size: 1rem;
    margin-bottom: 10px;
    min-height: 24px;
}

.calc-screen .result {
    text-align: right;
    font-size: 3rem;
    margin: 0;
}

.buttons {
    display: grid;
    grid-template-areas:
        "ac plus-minus percent division"
        "seven eight nine multiply"
        "four five six minus"
        "one two three plus"
        "zero zero dot equal";
    grid-gap: 7px;
    justify-items: center;
}

.btn {
    width: 60px;
    height: 60px;
    background-color: #333;
    border-radius: 50%;
    text-align: center;
    line-height: 60px;
    font-size: 1.5rem;
    cursor: pointer;
    user-select: none;
}

.btn:hover {
    filter: brightness(120%);
}

.btn:active {
    filter: brightness(90%);
}

.btn.zero {
    grid-area: zero;
    width: 100%;
    border-radius: 34px;
}

.btn.bg-grey {
    background-color: var(--grey);
    color: #000;
}

.btn.bg-orange {
    background-color: var(--color-accent);
}

@media (max-width: 500px) {
    .calc {
        margin: 0;
        border-radius: 0;
        width: unset;
        height: unset;
        position: absolute;
        top: 0;
        right: 0;
        left: 0;
        bottom: 0;
        box-shadow: none;
    }

    .calc-inner {
        max-width: 370px;
        width: 100%;
        margin: 0 auto;
    }
}