NeoNbx.kt

fun <I: Item> ItemContainer<I>.nbxShiftModified() {

    var item: I

    val slotsToShift = firstEmptySlot .. secondEmptySlot

    for (slot in slotsToShift) {

        item = items[slot]

        if (slot == slotsToShift.first) continue

        items[slot-1] = item
        
        if (item.isInvalidItem()) {
            secondEmptySlot--
            return
        }
    }
}