.code-boxes {
    display: grid;
    grid-template-columns: repeat(7, minmax(0, 1fr));
    gap: 8px;
    max-width: 420px;
}

.code-box {
    width: 100%;
    min-width: 0;
    text-align: center;
    font-size: 1.4rem;
    font-weight: 700;
    padding: 0.65rem 0;
    line-height: 1;
    text-transform: lowercase;
    border: 1px solid #ced4da;
    border-radius: 8px;
    background-color: #fff;
    box-shadow: inset 0 1px 2px rgba(0, 0, 0, 0.03);
    transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.code-box:focus {
    border-color: #3d8644;
    box-shadow: 0 0 0 0.18rem rgba(61, 134, 68, 0.22);
    outline: none;
}

.code-box.is-filled {
    background-color: #f1f8f2;
    border-color: #3d8644;
}

@media (max-width: 480px) {
    .code-boxes {
        gap: 5px;
    }

    .code-box {
        font-size: 1.15rem;
        padding: 0.5rem 0;
    }
}